Cooling System

[Devildawgusmc_1]

Okay, I have a 77 OMC Sterndrive 140 hp, that is causing me a lot of problems. I have replaced the impeller and housing, water circulating pump, thermostat and thermostat housing. I am getting water flow, but it is still overheating. I took the big hose off the thermostat housing and used a garden house to put water into the thermostat housing, it came out the hose so it is circulating water. I also used the garden hose to put water into both the smaller hoses attached to the thermostat housing, and the water came out the outdrive. After this, I filled up a trash can with water and let it run, the boat overheated. I don't know if I'm doing something wrong, or is there something else it could be?? Does the outdrive need to be submerged up to the point where the impeller is? I think it would be submerged more if I were to put it in the river. Would this fix the problem? I am getting good exhaust, but have not check the risers yet. Any ideas??

 

[Gary H NC]

Re: Cooling System

I doubt putting it in the river will fix your overheat problem. It could be manifold,headgasket or a number of things.
Does the engine run smooth?

 

[QC]

Re: Cooling System

Does it take a little while to overheat? After you fill the garbage can did you shut the hose off? I am guessing that you filled the can and then turned off the water. The water being circulated in the garbage can would theoretically get hotter and hotter as you have not provided a way for that water to cool, so it has to overheat as the water that is being returned to the garbage can is hot and them it is sent back to the engine and then it is hotter and so on . . .

I am not positive on this as I have never tried to run one without muffs, it would seem that if you let the hose run and replenish the can's water with cooler water that it should eliminate the overheat if all else is truly in good working order.

 

[Devildawgusmc_1]

Re: Cooling System

I was thinking that the trash can dosn't have enough water in it. There is a huge hole that when the outdrive is down, it meets up with another huge hole on the engine. Under this huge passageway there is a cage that doesn't look like it goes anywhere. I was thinking that this cage is where the boat sucks in some of the water from. This huge passageway is connected to the hole on the back of the outdrive (where I think water should be spitting out). When the boat is started, no water is coming from this hole.

 

[Mahoney]

Re: Cooling System

the cage hole you are describing is absolutely where the drive pics up water. If you are not running the engine with this hole submerged you might had destroyed the impellor.

The other big hole you are taling about is an exhaust port, it points straight back and is about an inch in diameter. no water will come out of there.

If you hook the hose up to the hose connector on the pivot point on the starbord side of the drive and turn on the water, water should come out of the cage hole.