94 merc 150 xr6 over heat

[markmc60]

we bought this boat last year, and the guy told us he had just replaced the water pump and gave us the old one.... curious, the "old one" looked new, should have been a dead give away. so, down the friggin rabbit hole we go. tried all the low hanging fruit, replaced the water pump, the stats, got a new water press gauge, new temp gauge. now we found some glimmers of hope, but never fixed the issue. and that was The tattle tell was weak like an old man peeing, no force and steaming ,never had any water pressure on the gauge to speak of. at idle it would do ok, off idle not real bad, half throttle and up, hot sumbuck in a minute. idle back down and it would cool off. hard to fish like that. I suspected blockage, just didn't want to do what I knew was wrong...... pull the power head and look at the exhaust plate gasket, pop the heads and the divider. now, it has been years since i worked on any outboard but engine cooling is engine cooling, no magic bullet. for the life of me I can't attach pics.... but i pulled the power head checked the exhaust plate where the water enters the head, gasket material some kind of black foam type stuff . pulled the heads and the exhaust divider (between the heads and dug crap out of the lower cylinders on the left bank, absolutely amazing how much crap was in there.

now this is long for a reason, i read a lot of threads here, and some were great, wish I could go back and give kuddos to the right guys, a couple were spot on correct..... so thanks to yall, I am convinced there are several with this same problem and keep chasin a phantom. well, I guess I'll scoot before the poo starts slinging and HUGE THANK YOU for the info from this forum

 

[Chris1956]

That motor is cooled at low RPM by the thermostats. At high RPM it is cooled by the poppit valve. Did you check/rebuild the poppit valve?

Have you checked the water intake holes in the gearcase for blockage. Often a broken piece of impeller will fall under the waterpump and clog that up.

Finally, check the cylinder heads for bolt torque. If there are compression leaks into the cooling system, overheat can occur.

 

[markmc60]

yes, I did............... found the stuff in there as I said

 

[markmc60]

view the photos, these shw where the debris was found, down in the exhaust plate uder the power head, stuck in the water ports of the 2 lower cylinders

 

[markmc60]

I looked back and these are the guys that I could not think of to thank
so, J_martin, faztbullet, charlieB

thanks...

 

[Chris1956]

So the motor is cooling properly?

 

[markmc60]

buttoning things up and will lake test it today or in the morning, I cant imagine it not being 100% better