Does this sound like a bad head gasket?

[dfrants]

I'm having issues with my 1994 Yamaha 130hp two stoke, Today I put in four brand new spark plugs and went for a ride, for about 5 seconds it ran at "full power" then dropped down to 4,000 rpms. Ran back to the dock and the #2 cylinder spark plug was black, the other three looked good. Does this sound like a bad head gasket?

 

[Chris1956]

Take a compression test to rule out head gasket. It sounds more like a bad ign system or flooding carb.

 

[racerone]

Inspect fuel pump diaphragm.

 

[99yam40]

so it went from fouling plugs to just fouling #2 plug now?

 

[dfrants]

Back when I ran the boat for several weekends then all four plugs, especially the two bottom ones would look fouled to me, this test took 20 minutes with four brand new plugs, I trolled out from the boat landing, opened her up, ran across the bay turned around and went back. Three plugs still looked "new", one was fouled bad.

 

[99yam40]

I am not sure which crankcase the fuel pump gets its pulses from, but as Raceron said check to see if it has leaking diaphragm

 

[dfrants]

Racerone was on the ball, I replaced the fuel pump and the gasket and that did the trick. Thanks, Guys!!!