force outboards run great cold but sputters and runs worse the longer it runs 1985 85hp

i have a 1985 bayliner capri with a 85hp force on it. boats ran great for years but had a little trouble last year. i put it in the water last weekend. it started up immediatly and seemed to run great at first, after about 10 minutes of runniing great even at full trottle it began to sputter which just got worse and worse the longer it ran. i docked and left it alone. the next morning i started it up cold and it ran amazing with no problems. but after about ten minutes it started to sputter more and more. its seems that it runs great cold but the longer it runs the worse it get. anyone have any idea on what the problem may be?

Re: force outboards run great cold but sputters and runs worse the longer it runs

May be running too rich or the stator is failing when is gets hot.

Re: force outboards run great cold but sputters and runs worse the longer it runs

last summer the fuel pump fell off the side of the block and exhaust flams were exposed to the side of the motor. ever since then its been running great cold but heats up and sputters. what do you think is causing this did something get fried. because the insolulation on the side of the cover was all burnt away.

Re: force outboards run great cold but sputters and runs worse the longer it runs

Check the diaphram in the pump.Is there a gasket sealing the pump to the block.You missing any hoses.Something loose.
Do a compression/spark test.Any water on the plugs?
Ethanol is messing up a lot of motors.It's delaminating the inside of older hoses causing clogs in the carbs and fuel filter.Check for soft hoses and junk in the filter on the motor.Check the diaphram J