Republic Seabee Engine Conversions

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Most Seabee owners and pilots agree that one of the few weak points of an original RC-3 Seabee is the lack of engine power.  The original engine installation was a 215 hp Franklin Model 6A8-215-B8F/-B9F six cylinder engine.  The Seabee is a large airplane and with the Franklin engine the power-loading is quite high.

The huge cabin of the Seabee invites pilots to overload the airplane, and on a hot day a heavy loaded Franklin-powered Seabee will be a challenge to get in the air...

Simuflight Lycoming GO-480 Engine Conversion
Photo: © Mark Becker

Engine conversions therefore have been among the most popular of the many modifications developed for the Seabee, after production ceased in 1947.   Many experimental one-of-a-kind engine installations have been developed, including gas turbine engines.  Some of the engine conversions have been STC'ed and are offered commercially by a few companies.  The Lycoming GO-480 geared engine conversions have become the most popular.  However, the Lycoming GO-480-series engines are no longer in production (since 1979).  Direct drive Lycoming IO/TIO-540 engine conversions have also been installed on a number of Seabees.   The O-540-series engines are still in production at Lycoming.

TAC Lycoming IO/TIO-540 Engine Conversion
Photo: © Randy Komko

The newest Seabee engine conversions to emerge are the Robinson V8 engine conversions, developed by Mr. Brian Robinson in Canada.  The Robinson conversions utilize a 320 hp LS-1 or a 350 hp LS-6 Corvette G.M. V8 engine.

Twenty-three Seabees have been converted to twin engine configuration, through the STOL UC-1 Twin Bee conversion.  Actually, the Twin Bee conversion is so extensive that it requires a new Aircraft Type Certificate.



Franklin Standard Engines


W.S.K. - PZL-Rzeszow
Ul. Hetmanska 12
PL-35 078 Rzeszow

The original engine installation on manufacture at Republic in 1946/47, was the 215 hp Franklin 6A8-215-B8F/B9F six cylinder.   The RC-3 prototype / pre-production aircraft originally had a Model -B7F installed.  The Type Certificate for the Franklin engines is currently held by a Polish company.

Specifications - Franklin 6A8-215-B8F/-B9F

Manufacturer Aircooled Motors, Inc.
Address Syracuse 8, New York, USA
Models 6A8-215-B8F and 6A8-215-B9F
Approved Type Certificate No. E-242
Weight - dry 432 lbs (incl. cooling fan and oil cooler)
Number of Cylinders 6
Rated Power 215 hp
Rated Speed 2500 rpm
Idle Speed 500 - 600 rpm
Reverse Propeller Speed (Max) 1750 rpm
Crankshaft Rotation Clockwise
Propeller Shaft Rotation Clockwise
Propeller to Crankshaft Ratio 1:1
Propeller Shaft Spline Size SAE 20
Cylinder Head Temperature Max. 525 ° F
Fuel Grade 80 Octane Nonleaded Aviation
Fuel Consumption (Cruise) 13.5 US gal/hr
Fuel Pressure 2 to 9 psi
Compression Ratio 7:1
Piston Displacement 500 cu in
Bore 5 cu in
Stroke 4.25 cu in
Fuel Pump Dual AC Diaphragm Type
Carburetor Marvel-Schebler MA4-5 # 10-3007
Ignition (-B8F) Dual Eisemann Magneto Model LA-6
Ignition (-B9F) 1 Scintilla Magneto + 1 Auto-Lite Distr.
Magneto Breaker Point Gap (Eisemann) .019" to .021"
Distributor Point Gap (Auto-Lite)    .020"
Maximum Drop on Magneto or Distributor  100 RPM
Ignition Timing 32 º Adv. Left and Right
Firing Order 1-4-5-2-3-6
Spark Plugs Auto Lite AH4
Spark Plug Gap .014" to .018"
Valve Clearance (lifter bled down, cold)    .040"
Starter 12 Volt, Delco
Generator (Max 35 Ampere) E.AL. GGS-4801A-EO-8686
Oil Capacity 13 qts
Oil Temp (Max) 260 ° F
Oil Pressure (Max) 50 psi
Oil Pressure (Idle Min) 20 psi
Oil Capacity (thru MSN 24065) 11 qts
Oil Capacity (MSN 24066 and on) 12 qts
Oil Specifications (Above 40 F) SAE 40
Oil Specifications (Below 20 F) SAE 20
Max Time Between Oil Changes 25 hrs



Continental IO-470-P Engine Conversions


N6432K (#682)
George Pappas Continental IO-470-P engine conversion
Photo: © courtesy of Nancy and Randy Rhodes

In the late 1960s, expert mechanic and world class metal craftsman George Pappas installed a 250 hp Continental IO-470-P engine in his Seabee N6432K (MSN 682) in Anchorage, Alaska, where Pappas owns a company called Aircraft Rebuilders.  Pappas also designed his special cowlings for the Continental conversion. His conversion also have a reversible propeller.

The original "Pappas" cowling was very sleek and beautiful, as shown in the above photo.  However, it seems that one of the later owners modified the cowling by widening the inlet, probably to improve cooling.

The Continental IO-470-P engine was originally installed on the Italian NARDI / SIAI-Marcehtti FN.333 Riviera amphibian.  The supply of IO-470-P engines is less than plentyfull and therefore this engine is quite expensive.  Actually the IO-470-P conversion has never been STCed.  However, at least four more Seabees are reported to have been modified with IO-470-P engines under 'experimental' category; N124AC (MSN 60), N6056K (MSN 231), N6668K (MSN 945) and N6747K (MSN 1035). 


Specifications - Continental IO-470-P

Manufacturer Teledyne Continental Motors
Address Mobile, Alabama, USA
Models IO-470-P
Approved Type Certificate No. 3E1
Weight - dry 472 lbs
Number of Cylinders 6
Rated Power (T/O) 250 hp
Rated Speed (T/O)      2600 rpm
Idle Speed ? rpm
Reverse Propeller Speed ? rpm
Crankshaft Rotation Clockwise
Propeller Shaft Rotation Clockwise
Propeller to Crankshaft Ratio 1:1
Propeller Shaft Spline Size SAE 20, extended shaft with provision for hydraulic propeller control and revering.
Cylinder Head Temperature Max. 460 ° F
Cylinder Barrel Temperature Max. 290 ° F
Oil Inlet Temperature Max. 225 ° F
Fuel Grade 91/96 Aviation
Fuel Consumption (Cruise) ? US gal/hr
Fuel Pressure -2 to +10 psig
Compression Ratio 8.0:1
Piston Displacement 471 cu in
Bore 5.00 cu in
Stroke 4.00 cu in
Fuel Pump ?
Fuel Injection TCM Injector (Eq. 5648)
Ignition (dual magnetos) ?
Magneto Breaker Point Gap ?" to ?"
Distributor Point Gap ?"
Maximum Drop on Magneto or Distributor  100 RPM
Ignition Timing 26 º BTC
Firing Order 1-4-5-2-3-6
Spark Plugs Auto Lite SH26. SH260
Spark Plug Gap  ? "
Valve Clearance (lifter bled down, cold)   ? "
Starter ? Volt
Generator ? Volt, ? Ampere
Oil Sump Capacity 12 qts
Oil Temp (Max) 235 ° F
Oil Pressure (Max) 100 psi
Oil Pressure (Normal) 30 - 60 psi
Oil Pressure (Idle Min) 10 psi
Oil Capacity 12 qts



'Daubenspeck' Engine Conversions


STC Bee, Inc.
10900 Rainier Avenue S.
Seattle, WA 98178

In the late 1960s engineer and Seabee owner Jack Daubenspeck, Seattle, Washington, started to develop Seabee modifications.  Daubenspeck soon formed the company Aerocraft Inc. and initially designed, produced and marketed some very popular fiberglass 'droop' wing tips for the Seabee.  He also started the design and development of new Seabee engine conversions utilizing the Lycoming GO-435/GO-480 geared engines. 

At some stage of the development, Aerocraft Inc. started accepting predelivery deposits from eager Seabee owners who wanted to give their Seabees 'new' power. Unfortunately, engineering problems continued and the company was forced to close down when some of the Seabee owners lost their patience and wanted their deposits back.  The prototype 'Daubenspeck' Seabee was sold to cover the claims, and was never flown with the Lycoming engine under Daubenspeck's ownership.

Seabee owner John Greeff did not loose confidence in Daubenspeck and contracted him to finish the Lycoming GO-435/GO-480 engine conversion for his Seabee, N6456K (MSN 707).  With Mr. Greeff funding the company, Greeff and Daubenspeck started the company 'STC Bee, Inc.' to produce and market Daubenspeck's Seabee modifications.  

For the ' Daubenspeck' engine conversion a new "scoop type" glas fibre cowling was designed.  Most Daubenspeck conversions will be recognized by this beautiful cowling.  However, it is generally agreed that the 'Daubenspeck' cowling is heavier (55 lbs vs 22 lbs) and less maintenance-friendly than the 'Simuflight' cowling.

The Daubenspeck Lycoming GO-435/GO-480 engine conversions were FAA approved on 13 April 1976.  Originally the 1976 FAA STC # SA-282-NW was issued for the Lycoming GO-435-series with 260 hp, the GO-480B-series producing  270 hp on 80/87 octane fuel, the GO-480F-series producing  275 hp on 80/87 octane fuel; and the GO-480C/G-series which puts out 295 hp on 100/130 octane.  Approval is for engines with rear mounted accessories and either splined or flanged output shafts.  Propellers for all approved engines are 84" diameter, three blade, constant speed and reversible.  Fabricated sheet metal parts for the STC kits were manufactured by Robertson (STOL) Aircraft.

STC Bee, Inc. went out of business in 1985, and Mr. Daubenspeck died year 2000.   In May 2004 it is reported that Jack's son, Mr. John A. Daubenspeck is working on re-introducing the 'Daubenspeck' conversions and modifications.

STC Bee held the following STC for engine conversion:

STC No: SA282NW - Installation of Lycoming GO-480-B1D (270 hp @ 3400 RPM), GO-480-G1D6/G2D6 (295 hp @ 3400 RPM) engine and Hartzell HC83X20-2CL propeller. [Issued 1976-04-13].  

Specifications - Lycoming GO-480-G1D6

Manufacturer AVCO Lycoming
Address Williamsport, Pennsylvania, USA
Models GO-480-G1D6
Approved Type Certificate No. E-275
Weight - dry 444 lbs
Number of Cylinders 6
Rated Power (T/O) 295 hp (GO-480-G1D6)
Rated Engine Speed (T/O)      3400 rpm
Propeller Speed (T/O) 2170 rpm
Idle Speed 500 - 600 rpm
Reverse Propeller Speed ? rpm
Crankshaft Rotation Clockwise
Propeller Shaft Rotation Clockwise
Propeller to Crankshaft Ratio 77 : 120
Propeller Shaft Spline Size SAE 20
Cylinder Head Temperature Max. 475 ° F
Cylinder Barrel Temperature Max. 350 ° F
Oil Inlet Temperature Max. 235 ° F
Fuel Grade 100/130 LL Aviation
Fuel Consumption (Cruise) ? US gal/hr
Fuel Pressure 2 to 9 psi
Compression Ratio 8.70:1
Piston Displacement 479.7 cu in
Bore 5.125 cu in
Stroke 3.875 cu in
Fuel Pump Lear-Romex
Carburetor Bendix PS-5BD
Ignition (dual) Bendix S6LN-21 (Left)
Bendix S6LN-20 (Right)
Magneto Breaker Point Gap .019" to .021"
Distributor Point Gap ?"
Maximum Drop on Magneto or Distributor  100 RPM
Ignition Timing 28 deg Adv. Left and Right
Firing Order 1-4-5-2-3-6
Spark Plugs Auto Lite AH4A
Spark Plug Gap  .016"
Valve Clearance (lifter bled down, cold)    .040"
Starter 24 Volt
Generator 24 Volt, 50 Ampere
Oil Capacity 12 qts
Oil Temp (Max) 235 ° F
Oil Pressure - Normal (Min - Max) 65 - 85 psi
Oil Pressure (Idle Min) 25 psi
Oil Sump Capacity 12 qts



Robinson V8 Engine Conversions


Robinson V8 Engine Conversion

Mr. Brian Robinson
Eric B. Robinson Ltd.
12 Hardwood Street, RR#3 
Kirkfield, Ontario KDM 2B0

Tel: 715-340-2408

The Robinson engine conversion is the newest on the market, and has stirred a huge interest among Seabee owners.  Developed by Canadian Brian Robinson, the conversion utilize a Corvette V8 automobile engine mated to a cast aluminum reduction drive designed specifically for the Seabee..  To date the Robinson's have developed & flown the 320 hp LS1 version & the 350 hp LS6 version.  Late 2005 the new 350 hp LS2  and 400 hp LS7 versions were installed in the first Seabees.

The conversions have been successfully flown using both standard Seabee 2 and 3 blade propellers and modern 4 blade MT propellers.  Robinson has also developed a system which uses the Hartzell constant speed reversible propeller from a GO-480 powered Seabee.

The engine can use both premium unleaded automotive fuel and 100 LL aviation fuel.

Photo: Registration: MSN: Engine: Remarks:
001 LS6 (405 HP) "Lake Tahoe Special"
Steve Lantz.
Crashed 2011-01-21.

Ex RC-3 Seabee
MSN 550

CF-EVE CF-EVE 003 LS6 (350 HP) Ex C-FZYL.

"Robinson Special"
André Durocher.

C-FCBV C-FCBV 006 LS? Frederick Robinson
CF-EJE CF-EJE 71 LS2 (350 HP) Planned conversion.
N87525 82 LS6 (350 HP) Under restoration.
Robert Fudald.
CF-HHS C-FHHS 281 LS7 (400 HP) Under restoration.
Donald Bradshaw.
CF-GZX C-FGZX 593 LS2 (??? HP) "Beeboyz Seabee".
C-FDLS C-FDLS 627 LS1 (320 HP) Cancelled as "destroyed".
Probably became another "VeeBee"...
LS6 "SeaBeast LS6".
Neil & Janet Kennedy.
N6466K N6466K 717 LS? Under restoration.
N64PN N64PN 749 LS7 "Seabee Warbird"
Peter Norman.
N378NK C-GLYI 001-23-007
LS6 (310 HP) "VeeBee - Amphibian"
Ken Kunz.
Ex CF-DKJ, N378NK.
CF-WCB CF-WCB 815 LS2 (350 HP) Under restoration.
CF-ILM (Photo: Blair Robinson) CF-ILM 001
LS1 (320 HP)
"Robinson Special"
LS6 (350 HP)
"Robinson Special"
Mike Lush.
C-FOME C-FOME 001 LS1 (320 HP) "Thunderbee"
Buzz Hale
LS? "Foster XB"
Steven Foster
CF-GAD CF-GAD 965 LS? "Seabee"
Henry Chapeskie.
C-GVEB C-GVEB 01 LS? Manfred Loos
"Seabee Special"

Robinson V8 Engine Conversion
Photo: © Brian Robinson

August 2005:

Brian Robinson reported that interest in the V8 powered Seabee continued to grow. Seven converted Seabees were flying, and four more were under conversion. The first U.S. licensed V8 powered Seabee is the "Tahoe Special". Rebuilt from the ground up by Steve Lantz & Paul Shepard, the Tahoe Special is powered by an LS6 coupled to a four-blade MT reversible propeller. The aircraft won the Grand Champion Seaplane award at EAA Airventure 2005 in Oshkosh! Based at Carson, City Nevada, they often fly from land or water with density altitudes in the 9000’ range. Steve & Paul consider the air conditioning essential for operating in their climate.

Total fleet time is approximately 1800 hrs.  The highest time V8 Seabee is Brian's own airplane CF-ILM.  It has accumulated 1176 hours.  The longest trip has been from Balsam Lake to Key West Florida and return.  They use whatever fuel is available, automotive or aviation. The aircraft continues to perform flawlessly. The V8 installation has been operated from sea to level to 10,000 ft, and in temperatures ranging from -20°F to 113°F.

November 2014:

We flew the original installation 2,098 hours in the period from 4 July 2000 to 23 Dec 2011. During that time the aircraft performed far above my expectations. The engine and PSRU was performing well when it was removed. We removed it because my system was becoming dated. My aircraft was the first V 8 conversion done. It was running an LS 1 with a manual throttle standard Seabee Hartzell 3 blade propeller and our 1.68:1 reduction ratio. Most of my customers use the 1.98:1 ratio with an electric throttle.

The Bee had a conventional (dated) panel and was in need of some upgrading. We refurbished ILM with many improvements including a new LS 3 sporting a modified Edelbrock supercharger, a new design single leaver control system that combines throttle, pitch, reverse & supercharger control functions in one unit, and a new design data link that allows the engine data to be sent directly from the engine control unit to the new MGL IEFIS based panel. The data link avoids the hassle of wiring in engine sensors and has the benefit of letting the pilot monitor the actual GM engine sensors that control the engine. 

We were back in the air 14 Jan 2014 and now have 99 hours on the new installation. I am really happy with the  performance of the new engine and associated systems.

I am sure ILM is one of most highly modified Seabee ever flown. The list of modifications are as follows:
(Ed: too long to list here, see C-FILM )

I have not documented any performance numbers. For them to mean anything I would have to calibrate all the instruments & standardize the data. Sufficient to say I have flown ILM in side by side comparisons with many Seabees, and none of them have come close to matching the performance. The LS 3 is a noticeable improvement over the LS 1. I have only had the new engine to 10,000’ but I was able to still pull 30” HG. Someday I will borrow an oxygen system and explore the higher elevations.

These days my focus has shifted from the Seabee to trying to raise capital to build the prototype of our new Horizon X2 - the first amphibian you can land on the water with the wheels down without hurting yourself!

Visit our website and check out the Conversion Kits/Current status and Horizon X2 tabs for more pictures and information.

E-mail dated November 21, 2014


The Robinson Horizon X2
The Next Generation Seabee!


USA Licensing Options

In the U.S. the only viable licensing option Robinson has been able to identify is compliance with the amateur built rules. In theory the aircraft could be licensed by using a one time STC or via the 337 processes. We have been unable to find an inspector willing to do this. The amateur built process is as follows

You currently cannot take a certified aircraft & license it as an amateur built aircraft. You can however build an amateur built aircraft using mostly certified aircraft components. This is only practical if the airframe is going to be refurbished. The process begins by removing the Manufacturers nameplate & ensuring the aircraft has been removed from the registry. You must then simply comply with the "51%" rule checklist. The only confusing part is that the 51% checklist has nothing to do with 51% of the work being done. It is simply a scorecard. You the owner must complete 51% of the items on the FAA approved checklist. There have been several Cessna 185 & 206 "replicas" built & licensed as amateur built aircraft. These aircraft are eligible for export to Canada & are permitted to cross the border. You may also import a Canadian amateur built aircraft into the U.S. It is important to note you cannot call the aircraft a Seabee. It must be called something else, e.g. A Robinson V-8 powered Bee. The name Seabee refers to a certified aircraft. If you call the FAA & tell them you are going to build an amateur built Seabee you will be turned down. If you call the FAA & tell them you are going to build a Robinson V-8 powered Bee (or any other name of you're choice) - an all aluminum, V-8 powered amphibian using modified Seabee components - they will inform you that you must comply with the 51% rule and instruct you to complete a 51% evaluation sheet. If your project meets the 51% criteria, it will be eligible for registration as an amateur built aircraft. The checklist is found on the FAA web site.

Robinson V8 Engine Conversions
C-FDOQ (MSN 934), CF-ILM (s/n 881) and C-GHQU (s/n 639)
Photo: © Brian Robinson

Below is a description of the protoype LS1 installation as installed on Robinson's Seabee CF-ILM.

Engine - The LS1, Corvette version, was a stock unit as purchased new from GM. It is rated at 345 HP @ 5600 RPM and produces 350 ft lbs torque @ 4400 RPM. The engine has been mated to a custom built 1.7:1 reduction unit. The engine was de-rated to approximately 320 HP by limiting the engine to 4500 RPM. This permitted the prop to turn @ 2600 RPM. (Maximum rating for the Hartzell Propeller installed on CF-ILM).  Robinson believed that de-rating the engine should help him reach his number one objective - reliability.  A large engine working at less than maximum power should last significantly longer than a small engine that is working it's heart out...

The engine was equipped with stock Corvette exhaust manifolds, machined to remove excess weight and mated to dual stainless steel mufflers. The mufflers and pipes were insulated reduce the heat buildup under the cowling.

The electric throttle body actuator was removed and replaced with the cable controlled mechanical throttle body actuator (KISS).

The engine was equipped with the stock GM air conditioning compressor.

The stock alternator was lowered to the same position used on the Camaro version of the LS-1 to provide clearance for the stock Seabee cowlings.

Reduction Unit - The reduction drive was custom designed to fit the Seabee installation using AutoCAD. It is based on standard Morse Hi VO chain and sprockets, and was sized and installed as per their technical publication. The chain is lubricated with engine oil via a spray bar.  Morse does not condone the use of their product in aircraft. The aluminum housing was cast, aged and tempered in a local foundry. All machining was done locally on a milling machine equipped with a digital readout. The design was loosely patterned off of the existing Franklin engine extension, with changes as required to maintain the existing thrust line and propeller position.

All thrust loads (forward and reverse) are carried by the rear reduction unit bearing. This is a copy of the Franklin setup and the thrust bearing used is the same as the original. The propeller pitch control system is identical to the Franklin set up. It has proven to be trouble free over the years. Oil return is by gravity to the engine sump, and all oil is filtered through a custom remote oil filtering system. The drive mates to the engine via a splined adapter bolted directly to the flywheel.  The heavy manual version of the flywheel was used as a safeguard against any potential vibration concerns.

Cooling System - The liquid cooling is provided by a stock Corvette radiator, complete with stock electric cooling fans controlled by the computer.  A manual over ride switch for the fans was added so that the pilot can turn the fans on anytime he pleases. The stock air conditioning condenser is mounted in front of the radiator as it is in the Corvette.

Fuel - Fuel is supplied via manually controlled dual electric fuel pumps, complete with a water separator and dual automotive filters. Operating pressure range is 58 - 62 PSI.  The LS1 will run on either premium automotive fuel or 100 Low Lead aviation fuel.

Engine Control System - The system chosen was a standard GM system. The unit is programmed with the export code for leaded fuel and uses no oxygen sensors. This was to enable owner to run 100 octane Low Lead fuel as well as premium unleaded fuel. It also meets the KISS criteria. The emission and VAT codes are suppressed. The computer is stock GM. After much research and correspondence, the wiring harness was purchased from an after market supplier. This portion of the project was as time consuming as designing the reduction drive. Robinson learned that it is imperative for a project like this to purchase the factory (not after market) manuals for the engine and read them thoroughly. You have to decide what is acceptable practice, how you want your engine management system to work, and have the harness manufactured accordingly.

The option of installing a second (backup) computer was discussed with many individuals. The resulting opinion was that the computer used is extremely reliable. The risk of a total computer failure is probably in the same league as a crankshaft or timing chain failure. The installation of a second computer would make the wiring harness considerably more complicated and increase the risk of a wiring harness/switching circuit failure. In the Robinson installation, Computer Power is supplied from one of two full size batteries. The batteries can be manually isolated in case of an alternator failure. The computer power source is selected manually.

Wiring Harness - The harness must be integrated into the airframe. Robinson believes that the odds of a wiring harness failure are greater than the risk of a mechanical failure (and you probably will get less warning). The harness utilizes crimped and/or soldered terminals. A good quality crimper was purchased and mil spec terminals and wires were used throughout. Routing, visibility, protection and security of the harness were installation priorities.



Manufacturer GM GM GM GM GM
Model Camaro LS1 Corvette LS1 Corvette LS2 Corvette LS6 Corvette LS7
Displacement 346 cu in 346 cu in 364 cu in 346 cu in 427 cu in
Bore x Stroke 3.90 x 3.62 in 3.90 x 3.62 4.00 x 3.62 in 3.90 x 3.62 4.125 x 4.00 in
Comp Ratio 10.1:1 10.1:1 10.9:1 10.5:1 11.0:1
Cylinders 8 8 8 8 8
Cooling System Liquid Liquid Liquid Liquid Liquid
Fuel System Multi-port Injection Multi-port Injection Multi-port Injection Multi-port Injection Multi-port Injection
Fuel Grade 91 Octane Unleaded or 100 Octane  91 Octane Unleaded or 100 Octane  Regular Unleaded or 91 Octane Unleaded or 100 Octane  91 Octane Unleaded or 100 Octane  91 Octane Unleaded or 100 Octane 
Ignition System Computerized Electronic - 8 Coils Computerized Electronic - 8 Coils Computerized Electronic - 8 Coils Computerized Electronic - 8 Coils Computerized Electronic - 8 Coils
Rated Power 325 hp @ 5200 rpm 350 hp @ 5200 rpm 400 hp @ 6000 rpm 405 hp @ 6000 rpm 505 hp @ 6300 rpm
Operating Power 300 hp @ 4500 rpm 320 hp @ 4500 rpm 350 hp @ 4500 rpm 350 hp @ 4500 rpm 400 hp @ 4500 rpm
Engine Torque 330 ft lbs @ 4500 rpm 350 ft lbs @ 4500 rpm 400 ft lbs @ 4400 rpm 385 ft lbs @ 4500 rpm 475 ft lbs @ 4800 rpm
Propeller Torque 463 ft lbs @ 2600 rpm 499 ft lbs @ 2600 rpm   549 ft lbs @ 2600 rpm  
Reduction Ratio 1.7:1 1.7:1 1.7:1 1.7:1 1.7:1
Brake Specific Fuel Consumption Ib/hr @ 3200 R.P.M. 0.507 0.454   0.500  
Cabin Heating Forced Air Hot Water Forced Air Hot Water Forced Air Hot Water Forced Air Hot Water Forced Air Hot Water
Air Conditioning Forced Air Mechanical Forced Air Mechanical Forced Air Mechanical Forced Air Mechanical Forced Air Mechanical
Exhaust System SS Pipes and Mufflers SS Pipes and Mufflers Ceramic coated stainless muffler system SS Pipes and Mufflers Ceramic coated stainless muffler system
Rec. TBO 1300 h 1300 h   1300 h  
Water Take Off 15 sec ? sec ? sec ? sec ? sec
Land Take Off 10 sec ? sec ? sec ? sec ? sec
Rate of Climb 1075 fpm 1075 fpm ? fpm 1125 fpm ? fpm
Power Loading 9.8 lbs/hp ? lbs/hp ? lbs/hp ? lbs/hp ? lbs/hp
Cruise Speed 110 mph ? mph ? mph ? mph ? mph
Fuel Consumption 10.8 US GPH 10.8 US GPH ? Imp GPH 10.8 Imp GPH ? Imp GPH
Range 714 mi 714 mi ? mi 714 mi ? mi
Endurance 6.5 h 6.5 h ? h 6.5 h ? h
Useful Load CDN @ 3150 Lbs 690 lbs ? lbs ? lbs ? lbs ? lbs
Useful Load US @ 3250 Lbs 790 lbs ? lbs ? lbs ? lbs ? lbs


Pratt & Whitney PT6A Turbine Engine


Mark Ward
SkyMark Aviation Services

David Saunders
AviaDesign Services Inc.

The Sea Hornet conversion has a Pratt & Whitney Canada PT6A-20 turbine engine, turning a specially built Hartzell 3 blade full feather, reversing propeller.  The engine has been de-rated to 400 SHP.

The subject Seabee is registered on the Canadian Civil Aircraft Register as C-GNVS (MSN 465).  The listed owner is Mr. R. Wallace of Bellingham, Washington, USA.  However, the modifications and flight testing are reported to be taking place in California.  From the photos it is also seen that the Seabee has gotten a serious 'nose-job'!  Also noted are the struts on the tailplane. The Turbine Seabee project has been named The 'Sea Hornet'.

The people behind the Turbine Seabee project - Mr. David Saunders (Avaiadesign Inc.) and  Mr. Mark Ward (SkyMark Aviation Services/AviaDesign Services Inc) - report that they already have accumulated a few hours on the 'Sea Hornet' and no problems have been experienced so far.  The Sea Hornet was also modified to get sponsons replacing the wing floats for water stability.  However, this modification was abandoned before completed.

C-GNVS (Photo: Bruce Hinds)

C-GNVS (MSN 465)
PWC PT6A-20 Turbine Engine
Photo: © via Bruce Hinds

Specifications - Pratt & Whitney Canada PT6A-20

Manufacturer Pratt & Whitney Canada
Address Canada
Model PT6A-20
Type Two-shaft axial-plus-centrifugal free-turbine
Take off power 550 shp to 70° F
ESHP 579
Max continous power 550 shp to 70° F
Max climb power 538 shp
Max cruise power 495 shp to 59° F



Simuflight Engine Conversions


Scott A. Henderson
McHugh Aviation Inc.
3763 Image Drive
Anchorage, Alaska 99504
Phone: 907.337.2860
Fax: 907.333.4482


The most popular of all Seabee engine conversions available is undoubtedly the Simuflight Lycoming conversions.  Developed by Joe McHugh, the Simuflight conversions represent the majority of all Seabee engine conversions installed.  Sadly Joe McHugh was killed as a passenger in an airplane accident on 16 June 2003.

In August 2003, Mr. Scott A. Henderson, announced that he and his sisters intend to continuing the legacy of their father Joe McHugh, as soon as the estate is sorted out.  They expect to be back in operation beginning in February 2004. Simuflight will be merging with KenAir Aviation Co. of Sonoma, CA, (Ken Thompson) and will be building a new facility in Fallon, Nevada. The plan is to offer complete Seabee maintenance and restoration at the new facility.  Restoration and maintenance work is scheduled to begin on 1 October 2004.

Simuflight has a huge inventory of Seabee parts along with all the kits that Joe McHugh developed through the years. McHugh salvaged every Seabee part he ever came across through the years and if you can't find it in Simuflight's inventory, then it most likely doesn't exist any longer.  Simuflight also have a number of critical parts that McHugh invested in having remanufactured before the originals were lost forever.

Simuflight will also be completing a number of STC's that McHugh had started but never finished. Seabee owners that need parts and kits are encouraged to make orders now, so that Simuflight can ship them before they move to Fallon.

All inquiries should be forwarded to the above contact information.

Both the STC Bee (Daubenspeck) and Simuflight Lycoming engine conversion utilize the the GO-435 and GO-480 engine series. The geared Lycoming GO-480 engine allows a reduced propeller speed, 2170 rpm at engine speed of 3400 rpm, with reduced noise as a result. Data for the GO-480 engine can be found above. Due to the higher mount of the Simuflight engine conversion, larger propeller diameters can be installed on the Simuflight (89")  conversions than on the Daubenspeck (84") conversions.

The main features of the Simuflight engine conversions are as follows:

Cowling - The Simuflight engine cowling is fabricated from two original Seabee aluminum cowlings that are modified to form on single piece weighing only 22 lbs.  The cowl is hinged at the forward end and opens with the release of two lever fasteners - one at each side.

Engine Mount - Is made almost completely of aluminum and weighs 14 lbs.  It has been statically tested and approved by FAA. The rubber "Lord Mounts" are mounted at 45º angle to the engine vertical.  The Simuflight mount is designed to transfer engine loads into the firewall and rear cabin, as on the original Franklin engine installation.

Exhaust System - Uses existing Seabee collectors which are welded to Lycoming flanges, to attach to the cylinders.  The exhaust is routed forward from the cylinders and exhausted upward over the center of the wing at a 45º angle, to prevent exhaust burn stains and to reduce noise.

STRuctural Modifications - The rear firewall section (triangular area aft of the rear spar) is lowered approximately 10 inches to make room for the carburetor or fuel injector unit.  An access door is provided on the left side for removal or inspection of the carburetor components.  The rear spar is strengthened on both sides directly under the engine mount.  Forward spar is strengthened by adding a stiffener below and with the use of a number of "Cherry Loc" rivets to further attach the web material to the forward spar.

Air Filetering - Carburetor induction air is filtered at the intake located forward of the engine to provide the coolest and cleanest pickup air.

Propeller - Hartzell constant speed and reversible 2 blade or 3 blade.  The blades are 9333, which are cut off four inches at the factory to give 89 inches blade length.

Gross Weight - The Simuflight engine conversions allow gross weight increase of Seabee from original 3150 lbs to 3250 lbs.

STC No: SA615NW - Installation of Lycoming GO-435-C2B, GSO-/IGSO-480 series and GO-/IGO-480 series engine with Hartzell HC-A2V20 and HC-A3VF series propellers; new nacelle and engine mount; modified front and rear spar and aft firewall; and associated systems. [Amended 1992-02-28].

STC No: SA5684NM - Installation of Lycoming GSO-/IGSO-480 series engine; Hartzell HC-A3V20 propeller; new nacelle and engine mount; modified front and rear spar and aft firewall; and associated systems. [Issued 1992-02-19].



T.A.C. Engine Conversions


Transition AirCraft, Inc.
P.O. Box 285
McKenna, WA 98558
Tel: 360-458-7715


Owned by Mr. Randy M. Komko, Transition AirCraft, Inc., (TAC), has developed the Lycoming IO-540 (250 - 300 hp) and Lycoming TIO-540 (300 - 350 hp) 'direct drive' engine conversions for the Seabee.  The TAC conversions utilize the 'Daubenspeck'-type cowling.   

In co-operation with other parties, Mr. Komko has also been involved in the development, installation and flight-tests of a number of GO-480-series engine conversions since 1976, including the the first GSO-480 (340 hp) Seabee engine conversion installed (N6124K MSN 310 flying on 1983-10-08).

Here is a list of some of the "TAC" Seabees:

Photo Reg. No: MSN: Year: Engine: Remarks:
N66CB (Photo: Randy Komko) N66CB 774 1976 GO-480 TAC # 1
N6684K (Photo: Alex McMahon) N6684K 967 1976 GO-480-G1B6
295 HP
TAC # 2
N37619 (Photo: Randy Komko) N37619 599 1979   TAC # 3

Rebuilt after 15 years under water.

N6119K 305 1980 IGSO-480 TAC # 4
N87576 (Photo: Randy Komko 1980) N87576 143 1980 GO-480 TAC # 5

Wreck purchased by TAC after crash in 1980. Under rebuild.

N6014K (Photo: Randy Komko) N6014K 184 1993 GO-480 TAC #6

Rebuilt by TAC after crash 1993.

N3500G (Photo: Randy Komko) N3500G
631   TIO-540-A2B
350 HP
N6522K 788   IO-540  
N6267K N6267K 477 1999 TIO-540-A2B
350 HP
N6144K N6144K
330   GSO-480-B1G6
340 HP
N6286K N6286K 499   TIO-540-A2B 
350 HP
N6381K N6381K 610   IO-540 
300 HP @ 2700 RPM
N6585K N6585K 858   IO-540
300 HP @ 2700 RPM

N6723K (Photo: Willam T. Larkins)

N6723K 1006   GO-435-B2C2 Crashed 2003.  Wreck purchased by TAC.
N245RC N245RC 245 2006 GSO-480 340 HP  
N6290K (Photo: Randy Komko) N6290K 503 1994? IO-540-K
300 HP @ 2700 RPM
N6124K (Photo: David Lednicer) N6124K 310 1983 GSO-480
340 HP?
N447ZK N447ZK 517 2012 IO-540
300 HP
MT Propeller.

Randy also offer several other Seabee modifications; including 6 place interior, droop wingtips, new wing floats, new spray rails.

TAC holds the following engine conversion STCs:

STC No: SA5652NM - Installation of a Lycoming TIO-540-A2B engine together with a Hartzell HC-E3YR-7LF/FLC8468-4R propeller.  [STC reissued 1992-03-31].

STC No: SA4330NM - Installation of a Lycoming IO-540-K engine (N6290K).

Specifications - Lycoming IO-540-K & TIO-540-A2B

Manufacturer AVCO Lycoming
Address Williamsport, Pennsylvania, USA
Models IO-540-K
Approved Type Certificate No. 1E4 (IO-540K)
E14EA (TIO-540-A2B Issued 1968-04-01)
Weight - dry 438 lbs (IO-540-K)
509 lbs (TIO-540-A2B)
Dimension (H x W x L) 19.60x34.25x39.34 in
Number of Cylinders 6
Rated Power (T/O) 300 hp (IO-540-K)
310 hp (TIO-540-A2B)
Rated Speed (T/O)      2700 rpm (IO-540-K)
2575 rpm (TIO-540-A2B)
Idle Speed ? rpm
Reverse Propeller Speed ? rpm
Crankshaft Rotation Clockwise
Propeller Shaft Rotation Clockwise
Propeller to Crankshaft Ratio 1:1
Propeller Shaft SAE A.S. 127 Type 2 Modified
Cylinder Head Temperature Max. 500 ° F
Oil Inlet Temperature Max. 245 ° F
Exhaust Gas temperature Max. 1650 ° F
Fuel Grade 100/100LL Aviation
Fuel Consumption (Cruise) ? US gal/hr
Fuel Pressure (above injector inlet air pressure) 25 to 45 psi
Fuel Pressure (above ambient air pressure) -2 to 40 psi (IO-540-K)
-2 to 65 psi (TIO-540-A2B)
Compression Ratio 8.70:1
Piston Displacement 541.5 cu in
Bore 5.125 cu in
Stroke 4.375 cu in
Fuel Pump ?
Fuel Injection RSA-10AD1
Turbocharger (TIO-540-A2B) TE0659
Turbocharger Compression Ratio 7.30:1
Ignition (dual) TCM S6LN-1208 (Left?)
TCM S6LN-1209 (Right?)
Magneto Breaker Point Gap ?" to ?"
Distributor Point Gap ?"
Maximum Drop on Magneto or Distributor  100 RPM
Ignition Timing 20 ºBTC
Firing Order 1-4-5-2-3-6
Spark Plugs ?
Spark Plug Gap  ?"
Valve Clearance (lifter bled down, cold)    ?"
Starter ? Volt
Generator ? Volt, ? Ampere
Oil Sump Capacity 12 qts
Oil Temp (Max) 235 ° F
Oil Pressure - Normal (Min - Max) 55 - 95 psi
Oil Pressure (Idle Min) 25 psi
Oil Capacity 12 qts



Turbomeca Astazou II Turbine Engine


Clark Cameron
Robert A. Mael


The Turbomeca Astazou II L turboprop engine installation on Seabee CF-MYT (MSN 1025) was engineered for owner (?) Bernard Robillard, Montreol, Canada, by Robert A. Mael; Northeast Engineering and Development Ltd. during the late 1970ies.  The installation was completed on 7 October 1980.

Turboprop Seabee CF-MYT (MSN 1025)
Balsam Lake, Ontario, Canada
Photo: © Blair Robinson

After skis had been installed on the Seabee early in January 1982, the Turbine Seabee made her first flight on 15 January 1982 with pilot/owner Clark Cameron at the controls.  Several test flights were made during January/February, achieving speeds in excess of 155 mph at 95% power, rate of climb 2700 ft/min at 100% power and fuel consumption of 12 US gal per hour at 55% power and cruise speed of 110 mph.

Mr. Blair Robinson kindly supplied the following additional information:

These photographs were taken at fathers dock on Balsam Lake, Canada.  Clark was a close friend of the family, & his Bee was based on Canal Lake, several miles from dads... This Seabee was designed, built & flown by the late Clark Cameron. He passed away suddenly walking away from the Bee after a test flight on skis. The airplane changed hands several times after his passing, but to my knowledge has not flown since Clark’s last flight.

I have many fond memories of the Ontario Seabee club meetings which were held at Clark’s house. He would often entertain the group by firing up the engine which was mounted in a test stand chained to his well to prevent it from moving. The engine was a Turbomeca Astazou. It was extremely noisy, his neighbors must have loved him! Many club meetings were spent debating the design concepts. If my memory serves me correct the engine was rated at 450 HP. Clark promised the DOT he would de-rate the engine to 250 HP. He was never able to figure out how to de-rate the engine and flew it with the full 450 HP. Clark owned his own machine shop and manufactured most of the components himself.

One of the pictures shows Clark in the middle, our dad Eric Robinson on the right and I am on the left. The day that these pictures were taken both dad and I flew Clark’s Seabee. Unfortunately Clark passed away early the following year. He proved the airplane would fly but never got the opportunity to complete the project or solve some of the issues such as hot starts, prop control, excessive noise and severely limited range. The airplane was operated under an experimental certificate only. My brother snapped these pictures with his Polaroid camera, we wish we had more...

CF-MYT is currently (since 1994-09-26) owned by Mr. Jean-Marc Rochette; 1905 Rte Du Domaine, St-Raymond, Quebec G3L 3A5, Canada.

Specifications - Turboméca Astazou II L

Manufacturer Société Turbomeca
Address Bordes, F-64320 Bizanos, France
Model Astazou II L
Type Single-shaft axial-plus-centrifugal turboprop
Approved Type Certificate No. ?
Weight - dry 348 lbs
Rated Power (T/O) 523 shp
Maximum Continuous 475 shp
Rated Turbine Speed (T/O)      43 500 rpm
Maximum Continuous Speed 43 500 rpm



W. E. Aerotech Engine Conversions


W. E. Aerotech Services
West 171 Sanderson Way
Shelton, WA 98584

W. E. Aerotech Services was run by Mr. Donald 'Don' Wallace and Mrs. Deborah Wallace Aerotech 'remanufactured' a number of Seabees until year 2000, when the company went out of business.  They also had under development a Continental IO-520 engine conversion.

STC No: SA00332SE - Installation of a Lycoming GSO-480-B2C6 engine (340 hp @ 3400 rpm) and Hartzell HC-A3CF-23L reversible propeller [Issued 1996-04-26].



Cukurs Engine Conversions


Gunars Cukurs


In Brazil Mr. Gunnar Cukurs operated several Seabees for more than 4 decades. During those years at least two one-of-a-kind engine conversions were developed by Cukurs and tested on the Seabees.  When the crankshaft of one the Franklin engines broke, the Franklin engine was replaced by an Argus AS10C engine from a pre-WW2 Focke Wulf 56 aircraft!  The engine had a power of 240 hp at 2000 hp.  Later a Lycoming GO-435 engine was installed from a Pilatus PC3 aerobatic aircraft.  Finally the now common GO-480-G2D6 engine conversion was installed.

Argus AS10C engine installation
Photo: © via Richard Cukurs


Lycoming GO-435 (?) engine installation
Photo: © via Richard Cukurs


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