88 Mercruiser 4.3 inboard overheating

[Kdissler]

I replaced the impeller, the thermostat and the risers were changed within the last 6 months... I bought the boat because I was told it just needed an impeller.. when I dropped the lower to change the impeller the plastic connecting pipe was melted so I changed the impeller the housing... one question the pipe coming from the upper unit seemed to be a copper pipe? Is that normal? I replaced the impeller and put everything back ran it and took off the hose at the thermostat housing and I have water flow.. it's like a faucet turned on half way without pressure... anyway I took it out yesterday and it was overheating out in the bay.. I gave it parked in a slip so dropping the lower is a little more difficult now... any suggestions??? Thank you in advance

 

[fastjeff]

The way Merc did these outdrive installations has always ticked me off! Why? No Tell Tale. The way you find out if the motor is pumping water is when the darn thing starts overheating! Stupid, right? (For that reason I;m installing one on mine, tapping off a riser and sending water flow out the back,, where I can see it.)

Back to your issue.... One: you still don't know if the impeller is pumping enough water, and, two: there could be a bad thermostat, or a blockage somewhere in the system.

Not sure where to look next, but I'd check her over with an infrared temp gun to see if the gage is telling you the truth.

Jeff

 

[faztbullet]

If it got hot enough to melt the plastic your going to need and pull the lower again.In the top of unit where pipe inserts is a grommet and gasket. Need to see if those are damaged or housing is warped. Also check power steering cooler for blockage as may be blocked by destroyed vanes of old impeller.