2.3 bayliner misfires and bogs down when revved up when warmed up to temp?

[Bayliner mike]

2.3 ford sohc bayliner... This boat misfires when warmed up... What could be wrong???? Every thing on motor has been replaced..... New timing belt/plugs/wires/coil/shift module/fuel pump/points/condenser... Have run out of ideas.... Is it possible to lose compression when hot?? Any ideas?

 

[Speak]

i had the same problem. turned out to be that one valve seat was cracked in the head. when it warmed up the compression would lower and the engine would miss fire. also water would leak into the combustion chamber thru this crack and mess up the fuel/air ratio. I found the crack by doing a leak down check thru the spark plug hole. put 150psi of pressure into the cylinder using a compression gage hose, then roll the engine over by hand to bring the piston up to top dead center on that cylinder. there should be no rushing noise of air. make sense?