87 Gamefisher 15 losing power

[whadam]

I got this motor with a boat fist time out the motor shut off acting like it was overheating. I replaced the water pump. Now it not overheating but when I am under power at WOT, after a while it starts pinging and losing power but under slight throttle it runs fine. whats up why am I losing power? Are the rings toast? It does take a quite a job to start.

 

[steelespike]

Re: 87 Gamefisher 15 losing power

Pinging would seem to indicate overheating.<br />Check for a thermostat.Examine the plugs.Be sure the plugs are correct.CAREFULLY feel the head.It should be too hot to hold your hand on but not so hot ot burns you.BE CAREFUL.<br />Check to be sure the stator is not advanceing too far.

 

[whadam]

Re: 87 Gamefisher 15 losing power

OK, I ran the engine at the lake no overheating. As a matter of fact I could hold my hand on the head all day. I can't see any way to adjust The timing. I replaced the fuel lines and checked compression, 120 psi on both cyl. still the same thing. the motor starts easy now after new plugs. It sounds like detonation. I am planning on decarbing this weekend. It runs fine for about 10 or 15 min. but then looses power. seems like rpms won't build after a while. it will run about half throttle all day long but, throttle up to wot and pinging starts and after a few min starts loosing power.