1978 OMC 800 Cooling issue

[hubertandrew85]

I have a 78 omc 800. at idle it cools stays 160 degrees. once you put a load on it get hot very quickly and so do the risers. I changed the impeller once. still did it. than i installed a crank mounted raw water pump on the front of the engine to pull water after the impellor in the drive. Still over heats very quickly. what am i missing here

 

[Scott Danforth]

welcome aboard.

did you inspect the risers and manifolds for rust and clogged passages?

 

[southkogs]

Have you greased the swivel bearing (exhaust can cause overheating sometimes)? Thermostat okay?

Welcome aboard.

 

[THE BEEF]

I'm betting on the swivel bearing seals leaking causing them to allow exhaust gasses to get sucked up in the cooling water, Give the swivel bearing 12 shots of OMC waterproof grease, the fitting is on the transom side ,a small hole. You need a grease fitting connector on a flex hose that will go through the hole. Push it in about 2 inches and you will feel a grease zerk. 12 shots and try it, if temp stays down change seal at the end of the season.
It is easier for the pump to suck exhaust gasses then it is water, I had the same issue.Thats what it was.
Good luck
The Beef

 

[THE BEEF]

I later read that you installed a raw water pump, If you don't remove the feed water hose and plug it going to the thermostat housing from the drive impeller pump it will still get exhaust gasses in the cooling water.