Overheating 2014 Mercury 3.5 hp four stroke

[SVSOLITAIRE]

Ok so I’m at the end of my rope. I bought a used merc 3.5 seemingly in impeccable condition. It started overheating after about 10 minutes of use.

Symptoms
-stops pissing and begins expelling steam at around 3/4 mile at mid throttle
-doesn’t start pissing till rpm’s raise
-gets sizzling hot at base of powerhead
-soot at top of driveshaft and surrounding area
-when it is pissing the water is extremely hot

Solutions I’ve tried thus far
- previous owner stated they just had the water pump and carb rebuilt
-new impeller
-I took apart and rebuilt the water pump again
-I replaced head gasket (my thinking was a blown head gasket would explain why it stops pissing when it reached high temp)
-I replaced lower powerhead gasket
-cleaned all water cooling ports from the supply line into the powerhead and thermostat housing


My final thoughts are that it could possibly need a carb adjustment. I am out of ideas and have scoured the internet. This is supposed to be my main dinghy motor so I’ve been a rowing son of a gun.

Any help in diagnosis would be greatly appreciated!!

[SVSOLITAIRE]

I forgot I also tested the thermostat and it works, I cleaned it in vinegar.

[bouncycastle]

No expert but if the piston rings are in not in correctly or oil ring is blocked up the extra friction can cause lots of excessive heat to build up .Typical problems are the piston ring gap is too small and with heat piston ring expands too much

If engine is running well in nuetral then it might be friction on the drive system any thing too big or unsuitable prop or excessive friction with gear box drive systems

Hope that helps

[SVSOLITAIRE]

So I got it sorted, and I could kick myself. It was a missing grommet that acts as a coupler between the inlet pipe and water pump. This is an example of assumption causing extra work. I assumed that the previous owner included all components of the water pump so when I took it apart then rebuilt it I just did it by what was there without looking over the schematic. I managed to fix it with a doctored GM part I got at Autozone while I wait for the replacement part to arrive. Well at least I have a new head gasket and driveshaft gasket [emoji23][emoji23]

[bouncycastle]

Thanks I learned something new

Hope it helps others

Probably over heating would have showed up running engine in nuetral that it had to be non drive chain issue