Not good...definitely not good

[ChrisfromVT]

Running at 90% throttle and motor dies abrubtly. '87 115hp tower of power. This motor has always been a good runner and I've kept up with maintenance properly...new water pump/impeller, carbs properly tuned, etc. When I removed the plugs, I noticed a piece of aluminum molded into the shape of the end of the spark plug blocking the lower end of the spark plug port. Must be a piece of melted piston or rings I guess, but I cant figure why the overheat.
I was having a fuel issue that I thought I narrowed down to 1 of the fuel tanks. I would be running on plane and suddenly lose power for a couple seconds before power would resume. Could those couple seconds at high revolution cause an overheat?

Thanks lads!
Chris

 

[Chris1956]

Re: Not good...definitely not good

The couple of seconds is a symptom of a lean running condition, I wil bet. That can cause your issue. Remove the transfer covers and inspect the damage.

 

[CharlieB]

Re: Not good...definitely not good

Any reduction in fuel supply to even one carb, can melt a piston with a quickness.

Sorry.

If you are really lucky you may have caught it soon enough that it is just a piston and not the cyl. Once finished rebuilding, be sure that you have found and cured the cause before hitting the water again.

Post pictures once you get the covers off and we can see what you find.

 

[Gomer50]

Re: Not good...definitely not good

Once you have aluminum shavings visable on the spark plug the piston has recieved some damage my guess would be from running on a lean condition.Removing the transfer cover will tell you.As you stand right now there probably isnt to much damage to the cylinder walls.Winter is here so I would tear into her hone out that cylinder,new piston and rings and figure out the cause.
Not to many $$$$ involved just some time if your comfortable doing this yourself.