Boat HELP!
 

So we have a 1976 (31 years old) Thundercraft with an 85HP Mercury. The problem is that every so often, mostly when started, the motor acts up. Even If we let it warm up.

When you hit the gas, the motor only seems to be at half to less then half power. Without touching the throttle, the motor will give bursts of power. Eventually the motor will have full power for the rest of the trip.

Now, we took the case off and looked for any obvious problem (leaks, something broken, checked the throttle linkedge) but found nothing. My ammature diagnosis is it has something to do with the injectors in the carb, or something to do with spark. Would carb cleaner be safe or could it bring debrise into the engine? Next weekend when we go up and I check the spark plugs wat are signs of problems, or where else should I check? My Dad feels there may be a cloged filter. Is there a fuel filter that could get cloged on a boat that old?

We are worried that there may be something catastrofic wrong like a piston is failing but its two-stroke there are no valves.


I guess what Im asking is what do you suspect this problem to be? What is the most likely senario?

P.S. Any1 know of a boat forum I could ask this on?

SeaFoam it ... SeaFoam was basically designed for marine use ( but can be used with basically any gasoline powered engine ) since.. err.. many many years ago. You can use it thru the intake, or oil or gas.
When was the last time you changed the plug on the motor? I"d get a replacement plug. You can always bring it back to the store if you don't need it..

When was the last time the oil was changed and what condition is it in?

You can now get Seafoam at Napa for under $10

P.S. SeaFoam also comes in aerosol can.. under Deep Creep.. and you lose bout 2 oz and more $$

IF you want to do only the intake style only.. I would use GM Top End Engine cleaner. ITs far stronger then Sea Foam, but I"m not sure how versatile it would be if you could even mix it in gas or oil

sounds like a filter problem to me..there should be a inline filter from the tank to motor...

Well since its two-stroke there is no oil to change, its mixed in with the gasoline.

What is sea foam actually? What is it designed to actually clean?

Here's Seafoam homepage

If you google it.. you'll find a lot of people with luck on it.. you can refine your search even further in google by putting seafoam marine in the search field

Yes.. I would also recommend lookin at the inline filter.
Easy way to test that is to bypass it and see if it does the same and or run another fuel line without a filter just for testing from a jerry can.