Engines > Restoration of Model Engines

Restoring a Gannet 4-stroke petrol engine

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Zephyrin:

Hi,

Recently I had the opportunity to overhaul a Gannet gasoline engine for a fellow at my club…Yes the Gannet, a large 15 cm3 4-stroke model engine, water cooled for model boat, from 1960, a famous vintage engine if not an antique one.

The contact breaker and its cam were totally out of use, and the old magneto looked in poor condition; so the owner wished an electronic ignition, for ease of start and faithfulness, to use it again in a model boat in the years to come...
I kept the magneto for further inspection, hoping to test it on one of my engine someday…

The rear crankcase cover with the bearing for the magneto was replaced by a plain cover and a new bearing for the camshaft was made, with a simple ring with a magnet on the camshaft and an adjustable support for the Hall sensor in front of the rotating magnet for adjusting the timing of the ignition. 

Combustion chamber and gas ports, heavily coated with burnt oil, were de-carbonized, and the valves and valve seats lapped. The piston rings were polished with an India stone as I suspected that the very sharp cut on the rings was the cause of the scratches visible in the cylinder liner, as the rings are really stiff.
The compression is tremendous, hand start will be difficult I fear !

The engine was then installed on a wooden test bench, with a tank for the cooling water, and then driven with a belt and the hand drill, a powerful but horribly noisy system.
A simple stream of butane in the intake lets hear the first explosions once the ignition was properly set, very encouraging for the next step : running on plain gasoline !
The carburettor -of very simple design- is put in place, with a fuel tank.

From the first turns, it appears that a "positive” water cooling with a flow of coldwater in required,  a simple convection is very insufficient; the engine becomes shortly extremely hot, therefore I add a small water pump for the continuation of the tests, not to risk a seizure!

A muffler also is mandatory as the noise is on the high range !

The carburettor was also isolated from the very hot cylinder head with a thick gasket. The engine responds immediately to the throttle, up to 8000 rpm, very sensitive, the idling near 2300 rpm is very rich, (hence the carbonized exhaust ways) being easily flooded too, I would recommend a more efficient carburettor for long and pleasant runs when installed in a RC runabout or other speedboat.

the tests:
http://www.youtube.com/watch?v=R0WqUJZ70q0
 and other pictures of the repair
https://photos.app.goo.gl/M8sPA3qbg6rz43bG6

Cheers

Roger B:
Excellent  :ThumbsUp:  :ThumbsUp:  :wine1: Quite a beast  8)

Jasonb:
That's running well again. I've always liked the look of these engines in the Miniature Engineering Museum's albums.

Do the two cams sit either side of a central skew gear and if so are the cams and gear all cut from the solid or are they separate parts fitted to a shaft?

michaelr:
Now that brings back memories of my model boating days way back, I had a 15cc Magneto Ignition Gannet a fine engine in it's day it was very reliable always a good starter.
A couple of pictures of my boat.

Zephyrin:
Hi;
RogerB : yes, impressive, a great change from my diminutive engines…

Michaelr : wow, great pictures, this is exactly the project of the owner of this engine, in a large Chris-Craft look alike model, with a nice bow wave.
A difficult point will be to find a pond where combustion engines are allowed...
JasonB :
the two cams are separate parts in very tough steel pined to the shaft on both side of the bronze helical gear.

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