Omc 400 stringer 3.0 140 HP overheating problems

[misiek]

I have a 1987 Thundercraft with OMC 3.0 140 HP and 400 stringer out drive. The engine is running very hot. I have replaced the temp sensor, cleaned the exhaust manifold and riser. Is there anything else besides the impeller that could cause the engine to overheat. I have replaced the engine because of a cracked block. The old engine did not run hot. Replaced it with an older OMC. Used all of the outside components from the replaced engine. When all done tested it on the lake and noticed the engine overheating. Any ideas. And my final question - is it possible to replace the impeller without removing the whole drive. I really don't want to mess with the cables on the out drive. I'd appreciate all of your input. Thank you.

 

[GMC2003]

Re: Omc 400 stringer 3.0 140 HP overheating problems

If the thermostat isn't opening, the engine wont cool. I have no clue about the impellers on that year.

 

[superbenk]

Re: Omc 400 stringer 3.0 140 HP overheating problems

It's got an impeller just like anything else in the outdrive. Could be due for a change. Hopefully you don't have anything blocking cooling passages anywhere.

 

[misiek]

Re: Omc 400 stringer 3.0 140 HP overheating problems

I took the thermostat out and the overheating went away significantly. I was a new thermostat. I can't believe it would be main cause. I still need to test the impeller while on the lake though. Thanks guys.

 

[Howard Sterndrive]

Re: Omc 400 stringer 3.0 140 HP overheating problems

you can apparently just kinda split the drive and support the lower while you work on the upper (upside down) and replace the impeller that way, if you don't want to remove the cable. I gotta think my neck would snap in two working upside down in there, but maybe it's not that bad - I haven't tried it.