Had a new to me boat out a few times, 2010 Mercury Optimax 90hp 1.5. runs 4,000 rpms just fine around 9 psi or so.
i get an overheat alarm and some smoke out the top if I go WOT. I have tried to pay attention to the stream of water and it doesn’t look as strong as it could be. The previous owner just had the pump replaced so maybe that guy didn’t do the gaskets and the job correctly....
I was bored waiting for parts so I took apart the poppet valve and thermostat, I’ve monitored the thermostat to know it opens around the 140 mark. First time I’ve seen a poppet valve and the rubber housing in person but it all looks good. There was no residue or buildup in either area. I also took out the compressor strainer and it too was 99 percent clear. I know you’re supposed to start with water pump first, ....
im going to replace thermostat and poppet while I have it open and I’ll do the pump, all new gaskets, full kit etc. hoping my issues are better.... I also heard from a merc tech that some guys have to even put some silicone or other sealant around a part of the pump to help it too....
any other items I should be looking at or am I crossing all the important stuff off the list? I can run 30mph fine with no alarms but anything more than that I feel like the pump is getting like 7-9 psi at WOT.
lastly, does anyone have a link or know the exact size for the O ring in the oil pump? I have a perfectly working oil pump that leaks, just annoying.... I’ve taken that apart and know the priming sequence with the computer.... I was a fool and didn’t replace the o ring when I had it apart because it looked fine. Thought maybe a bolt or two was just loose.... I was wrong, there’s gotta be an o ring that can stop the leak .....
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