1981 omc 2.5 still having overheating issues

[ez4sure]

hi guys still trying to figure out why this boat is running to hot. so first running with the muffs or having the lower unit in a tub of water as seen in the pic it takes about 30 seconds for the lower unit to start pumping but when i back the boat in the lake it pumps good right away so is there more water inlets besides the three holes on each side of the lower unit and i put clear hoses from the manifold to the thermostat housing water coming in no bubbles at all, water going back to manifold i can see a steady stream of small bubbles. also the back two cylinders have lower compression the test i did this morning was engine cold #1 115 #2 115 #3 110 #4 105 so maybe possible blown head gasket? yesterday running in the lake the temp gauge was going up and down some thanks

 

[Grub54891]

The tub of water is not enough. It needs to be much deeper,as the impeller should be submerged. Gave you changed the impeller, and thermostat?

 

[Scott Danforth]

This should be merged with your other thread

Attempting to suck from a bucket simply burned up your impeller.

So now you get to pull the drive back apart to replace the impeller

If you want to suck from a bucket, the bucket needs to be big enough to get the whole outdrive submerged as the pumps are not positive displacement pumps and do not self prime. To get the drive deep enough, the bucket would need to be big enough to put the boat in it.

either use the flush port on the trunnion cap, or use muffs

 

[ez4sure]

Yes impeller thermostat sending unit and gauge replaced

 

[Bondo]

Yes impeller thermostat sending unit and gauge replaced

Ayuh,..... Usin' that bucket, you've probably already burnt up the new impeller,.....

The raw water pump is a flooded entry pump, as Scott explained,.....

 

[ez4sure]

hello everyone thought i should give you all a update pulled lower unit back off to check impeller found that the upper gear case has water in it, impeller is still good. i just put all new seals in a few months ago but the seal behind the water pump is leaking between the seals and case after closer inspection the housing where seals go in are a little deteriorated so i guess i need to use something different to seal the seals in with, i used aviation form a gasket last time. any suggestions on what non hardening sealer to use. also think i figured out the overheating problem with the lower unit off i ran the motor with the garden hose going to the riser still ran hot then i pulled the thermostat out and it was plugged up with chunks of rust so i pulled the head off and freeze plugs out and got as much rust out of the engine as i could the back of the block had alot of bigger chunks of rust and pieces off silicone gasket sealer put the head back on ran it without a thermostat and it would not heat up enough to move the gauge, so then i put in the 140 thermostat that it had in it when i bought it and it ran at 140 so then i cleaned up the 160 thermostat and with it in it runs hot around 190 so i guess that is a bad thermostat. so if i can get that upper gear case sealed i should all set.