Burnt Pistons

I have a 1976 70 Horse. The over temp horn has not gone off and I have always ran more than enough 2 cycle oil in the tank. I find the math is easier at 3 oz per gallon. I removed the head and found that the top piston is burnt and the middle looks like it is starting. I put the head back on and ran a compression check and was amazed to see all three pistons were around 110lbs. The water pump is the original from 1976 as far as I can tell.

Would you guys recomend replacing the water pump impeller? Is there a test I can do before I do it? Also, should I do anything about the burt pistons. A new power head or rebuild is out of the question. One more question do you think a failing water pump or not enough oil in the fuel burt the piston.

Any help would be greatly appreaciated.

Re: Burnt Pistons

replace them impeller with a water pump kit, and do a decarb. as long as you got good compression run it.

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

Re: Burnt Pistons

By burnt you mean blackened with carbon right. Not a crator of molten aluminum.
Decarb like prescribed and do it yearly. Some guys regularly run seafoam in their tanks for continuous protection. Sounds like you caught her just in time.
If you do alot of trolling it would be worth it to get a mixing bottle and run a 50:1 mix. A nice WOT run prior to heading for the dock will help burn up any buildup as well.

Re: Burnt Pistons

Thanks for the advice. I will give it a try...