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25 Yamaha 2 stroke pumping issues

L

lkas

New member
I have a 2 stroke 2010 Yamaha 25hp outboard. Recently after using the boat I noticed the outboard wasn't pumping when I went to flush the motor.After inspection it was clear the inlets were not clogged, or the tell-tale outlet, so I bough a new impeller and replaced it, though the old one looked in pretty good condition so I'm not sure that was the issue in the first place (maybe just poor hose pressure or bad earmuff connection). I also checked out the thermostat and put it in hot water - it opened up fine, but I'm not sure what the exact temperature was (maybe its opening but not at a low enough temp?) After hooking it up to a hose with good pressure I got it pumping water again. Thinking it was fixed I went out this weekend, however the motor was not pumping as much as it usually did and often would cut out intermittently, and completely when at idle (maybe my dumb ass put the impeller in backwards?). There also seemed to be more smoke coming out of the exhaust relief holes than usual. As it was still pumping I kept using the the boat, and kept feeling the head unit to check it wasn't too hot. Which was a very questionable move it seems, as after about 15 mins just putting along slowly there was a hiss and a lot of smoke billowed behind me. I assume this was unquestionably a blown head gasket, so switched it off and used the electric trolling motor to get back to the boat ramp. I called up the mechanic and they have a 2 -3 week wait. Patience got the better of me and after removing the spark plugs and spraying some WD 40 to stop any corrosion I decided to remove the head to see the damage, however both the water jacked and head gasket look perfectly fine, and there was no sight of water intrusion so to me that says a blown gasket does not seem to be the issue. As its obviously clear by now my diagnostic skills are very poor and it would be great to hear some thoughts from smarter souls out there on what the issue could be.Thanks in advanced!
 
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