78 OMC 240 still overheating

[dhughes214]

Ok, so my boat is still overheating, but only at high rpms. Approx 3500 and above. I pulled the drive off, and changed the impeller, seals, everything. it pumps water to the motor like a champ now. I also pulled the hose off that comes from the radiator (heat exchanger? I don't know what the boat term is) and water is circulating great through there. My swivel bearing housing has brand new seals and is full of grease, so I'm not pulling exhaust gasses. My next step will be to pull the risers and make sure they aren't plugged, but I have plenty of water coming out of exhaust, so I don't think they are the culprit. What else should I check? I heard something about timing being advanced too far causing this issue, but the motor runs strong, so I'm skeptical. Any ideas greatly appreciated.

 

[southkogs]

Thermostat?

 

[gottaboatnow]

If you have power steering on yours, please read this. A friend of mine with that same combination told me that it's the power steering that caused his overheating problems. Remove the belt from the power steering pump and it will not overheat, assuming everything else is okay. Never did figure it out and the boat is a bit hard to steer at very low speeds, but otherwise, you can't tell the difference. Worth a shot?

 

[southkogs]

I didn't know the tru-course had power steering available. That's interesting.

 

[dhughes214]

Just replaced the thermostat today. Put in a 160 which is what was originally in it. Had a 180 in it before. No power steering. Oil looks good, plenty of water circulation. manifolds stay nice and cool. I am at a loss.

 

[dhughes214]

Does anybody know how hard it would be to eliminate this enclosed cooling system and go to raw water?

 

[user-name]

Remove the heat exchanger and fill both water sides (raw&fresh) with vinegar .flush and fill see if that works.

better yet take to a local radiator shop and have it cleaned.

 

[dhughes214]

Had radiator cleaned. No dice.

 

[user-name]

Wow i dont know where you live.
do you have a minnisota boat (freashwater) or a washington boat (saltwater)

Ilive in washington

look in this thread http://forums.iboats.com/forum/engi...drives/587118-1977-omc-electric-stringer-help the 8th picture

the hole in the tube

 

[dhughes214]

I live in norcal. No saltwater for this boat. Would much rather convert to raw water cooling. Although if I can get this to cool correctly thats fine too.

 

[user-name]

What is getting hot? manifolds or your antifreeze?

Have you pressured checked the motor for a blown head gasket.?

Also have you checked your rad cap?

 

[user-name]

Also have you flushed the block?

 

[dhughes214]

Ha! Were on the same page. Just did the test today to check for headgasket leak. Its good. Also put on a new radiator cap yesterday. And I have flushed the block twice. I still havent checked the risers/manis yet. My thoughts are clogged risers, timing is off, or circulation pump is going bad. Pump is original which makes it 36 years old. Heat exchanger is original also. The tubes are pretty clean. But it could still be my problem. I'd really like to bypass it. My father has a 91 thats got the same setup as me just newer. 351 windsor with cobra outdrive. His boat is raw water cooled. Were gonna look at his setup and try to set mine up the same way.