1979 OMC 120 Sterndrive runs very hot at low RPM

[Boomyal]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

Well if you can hold your hand on the exhaust manifold AND you have tested the flow at low RPMS then IMHO the outdrive pump is supply sufficient water to cool. They regulate the flow of water thru the exhaust manifold so as not to continue to shock it with too cold of water.

I would concentrate on motor issues like timing? Not sure what else. It would be hard to believe that you have a flow issue thru the block.

 

[skipbehr]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

I had the same problem omc 800 stringer with 302 v8. heated up when running slow,but would cool to normal when running 3/4 throttle.
turned out to be a worn plate under water pump impeller. hope this is helpfull.

 

[Boomyal]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

..........I had the same problem omc 400 stringer with 302 v8......... .

????400 Stringers were not used with V8's?????

 

[superbenk]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

I had the same problem omc 400 stringer with 302 v8. heated up when running slow,but would cool to normal when running 3/4 throttle.
turned out to be a worn plate under water pump impeller. hope this is helpfull.

I hope that's a typo. If you were powering a 400 Stringer with a v8 you were on the path to bigger problems than temps!

 

[lakedog]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

We took the boat to the bigger lake here around Dayton this weekend. I have changed nothing since the last time we put her in the water. We ran her for about 5 miles of water had her in for about 3 1/2 hours and she never got hot once. Stayed right at 160? the whole time. We stopped started ran slow through the no wake areas and even spent a good bit of time around the dock waiting to get out because it was rather busy. No worries. Got to thinking though about the heating up around the dock at the smaller lake. We are fairly sure there is a good bit of grass in the shallow water near the dock because you can see it and we always pull some up with the trailer when we take the boat out. Maybe it was simply sucking it against the intakes and we were not getting enough water because in that lake which is a good 30 feet deep or more in most of the lake we had no problems anywhere else. We (my wife and I) were both very pleased with the voyage we even got a chance to put up the Bimini top and enjoy some time in the sun. So We are now looking forward to some outings with her family. Thanks very much to all who helped in this thread.

 

[Boomyal]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

......... we even got a chance to put up the Bimini top and enjoy some time in the sun. ........

That statement is an oxymoron! However, that seems to be about the same way that my new PNW neighbors enjoy the sun; by staying out of it.:laugh:

btw, you did not address the issue of having a 400 stringer drive, with a V8?

 

[lakedog]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

I agree that is an oxymoron about the Bimini top and the sun. However I am not the one who said they had a 400 stringer drive with a V8. That was Skipbehr.

 

[skipbehr]

Re: 1979 OMC 120 Sterndrive runs very hot at low RPM

Yep typo I meant to hit 800 stringer> sorry!!!