reason for 90 hp v4 pistons failure

[JoshKeller]

well guys, another twist. my older friend found an 85 hp powerhead for cheap, we checked it out, and threw it on his mid section.. i put a new water pump impeller in to be sure. a month and a half later, he calls me distraught saying its running rough at idle and coughing again. i took a comp test and hot port of 108, 110, starboard 95 and 100. pulled the head and exhaust cover and found the same exact thing that happened to the last powerhead. im thinking possibly a intermittantly bad thermostat, even though i tested them? what else could it be? lyckily it was caught before the rings broke, so a hone job and new pistons and rings should fix it, but what could be going on here? this block has never been opened up best i can tell, and for sure has never been bored over.

[Motv18]

Blow another power head put a water pressure gauge on it. He could be running it dry.

Also the ever popular forgot oil.

The new ph more or less eliminated everything but that and supper common omc issues.

[gotboostedvr6]

Crossflows are everywhere and often very cheap. Find another ph or complete motor and get him a water pressure gauge.

Several plaques around the boat that remind him to add oil will not hurt.

[JoshKeller]

is there anything in the mid section that could cause an issue? i did flush the water tube out before we swapped the powerheads - but two powerheads with the same issue is baffling me. is there a test to verify the overtemp sensors work properly aside from just the horn test?

[racervboat]

Its an old used powerhead with years of time on it.They are notorious for carboning up the rings and sticking then they catch a port and its all over. I only rebuild about 10 a year so I don't know what the heck im talking about.?