Mission Profile

Takeoff - Typically maximum power for one minute. Limit Maximum power use to five minutes continuous.

Cruise - Typically requires 140 H.P. to 160 continuous H.P. @ 100 to 110 M.P.H.

Altitude - Most missions are flown between 1000 ft ASL and 3000 ft ASL. Occasional excursions to 10,000 ASL

Duration - Most missions 45 minutes duration. Maximum duration approximately 6 hours.

Fuel - Must be able to use both leaded and unleaded fuel

I believe it is important to identify and publish the project objectives and define the mission profile prior to starting the project. Review and modify them often. You will be faced with many engineering compromises during the project, and reference to the objectives often provides guidance in the decision making process (e.g. is it wise to "hot rod" the engine if reliability is the major objective?)

The next step in the process was to read as much about engine conversions as I could, and talk to everyone I could identify as being involved with a conversion. Thanks to the internet and the telephone I was able to quickly gather information. My research suggested I should use a "stock" Chevy 350 aluminum engine and mate it to a chain drive. I believe the chain drive minimizes the risk of vibration issues caused by coupling the drive to the engine.

To minimize any effects the conversion would have on the Sea Bees flying qualities, I decided to keep the original engine thrust line and propeller location. I had been hoping to use a Geschwender drive unit. Unfortunately, it was 10" to short to meet my requirements. The good news was that Fred Geschwinder was a very helpful individual and encouraged me to develop and build my own drive to suit my needs. Over the course of several lengthy conversations he patiently answered all my questions and made many helpful suggestions on how to approach the conversion. My original plan was to buy his drive and build an engine. Fred suggested I build the drive and buy the engine!


The LS-1, Corvette version, is a stock unit as purchased new from G.M.. It is rated at 345 H.P. @ 5600 R.P.M and produces 350 FT Lbs. Torque @ 4400 R.P.M. The engine has been mated to a custom built 1.7:1 reduction unit. The engine has been de rated to approximately 320 H.P. by limiting the engine to 4500 R.P.M. This will permit the prop to turn @ 2600 R.P.M. (Maximum rating by Hartzell Propeller for the model I have). I believe de-rating the engine should help me reach my number one objective - reliability. I believe 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 is equipped with stock Corvette exhaust manifolds, machined to remove excess weight, & mated to dual stainless steel mufflers. The mufflers and pipes have been insulated reduce the heat buildup under the cowling.
  • I removed the electric throttle body actuator and replaced it with the cable controlled mechanical throttle body actuator (KISS).
  • The engine is equipped with the stock G.M. air conditioning compressor.
  • I lowered the stock alternator to the same position used on the Camero version of the LS-1 to provide clearance for the stock Sea Bee cowlings.

Reduction Unit

The reduction drive was custom designed to fit the Sea Bee installation using Auto Cad. 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, so why change it. 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. I used the heavy manual version of the flywheel 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. I added a manual over ride switch for the fans so 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 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 LS-1 will run on either premium automotive fuel or 100 Low Lead aviation fuel.

Engine Control System

The system I chose is a standard G.M. system. The unit is programmed with the export code for leaded fuel and uses no oxygen sensors. This was to enable me 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 G.M. 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. Before undertaking a project like this, it is imperative 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 you're engine management system to work, and have the harness manufactured accordingly.

The option of installing a second (backup) computer has been discussed with many individuals. The resulting opinion is 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 my 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. In my opinion, 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. I purchased a good quality crimper and used mill spec terminals and wire throughout. Routing, visibility, protection and security of the harness were installation priorities.

Status (Oct. 2000)

I have approximately 56 hours on the finished product, including a very enjoyable trip to Airventure 2000. The unit has surpassed all my expectations to date. The lake I fly from has an elevation of 842' above sea level. On a 76 degree day, calm water, two people and 2 hours fuel, takeoff times are in the 13 to 15 second range, and climb is a solid 1000' per minute. Not bad for a 53 year old amphibian! At gross the take off time is 21 seconds and climb is 750' per minute. The heating and air conditioning are great additions. Using a power setting of 23" manifold pressure and 3300 RPM, cruise fuel consumption is 8.5 imperial gallons per hour at 110 M.P.H. indicated. This compares to 10 Imperial gallons per hour at 100 M.P.H. for the Franklin. The only area I would like to improve is reducing propeller noise. The mufflers significantly reduced my noise footprint, but the propeller still noisier than I expected. If anyone has suggestions for propeller noise reduction, please let me know.


This is an original design and has worked well to date. However I believe strongly in learning from the success and failures of others. If you have any suggestions or concerns with my project, please do not hesitate to call me or E-mail me.

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