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Old OMC Buick Overheating 1971 225

J

jhill51

New member
I've got a '71 Kenner with an OMC 225 Buick V6. The boat overheats at high speeds but runs just fine at low speeds and idle. We've tried everything. We can verify that water is passing through the engine, we've pull hoses and checked every point that we can. Head gaskets have been replaced, water pump has been replaced. We pulled the manifolds to verify that they were clean and clear. We hired the marina mechanic to replace the tailshaft impellor.

Anyone ever seen this before? Boat runs great otherwise.
 
Re: Old OMC Buick Overheating

grease the swivel bearing well.

the grease (and a lip seal in the exhaust hsg) keeps the water pump from sucking exhaust gases
 
Re: Old OMC Buick Overheating

Do what Hy says know where the zerk is ? Turn the wheel all the way port, there is a hole in the upper on the front of the drive. Inside that hole is a zerk fitting.

Ok after running the boat on the water i hope that fixs your problem, if it doesn't, then check your t-stat.

I didn't see anything in your post about the t-stat.

I didn't see anything about heat exchangers ?

So the hose that comes in from the transom goes where? Say it goes to the t-stat, pull it off at the t-stat and with water going to the drive start the motor, how high is the water shooting straight up ? Quick shut off the motor, 3-5 seconds is all you need to run it.

Post back here and we, all together will try to trouble shoot your problem. And try to have a good outcome for you.
 
Re: Old OMC Buick Overheating

Thanks for the replies. I forgot to mention that we changed the thermostat.

I'll look for the zerk fitting and try that next and get you a response on how high the water shoots when the hose is disconnected.

Heat exchangers I'm assuming are the pieces where the water flows through over the manifolds? What am I looking for there?
 
Re: Old OMC Buick Overheating

power steering cooler maybe , this a raw water cooled motor? Did you ever pull the risers to see if they are blocked up and inspect the flappers. Maybe a flapper fell down and is blocking the exhaust.
 
Re: Old OMC Buick Overheating

He's probably got the same set up I do...only newer. When I took apart my Risers to clean and repair last fall, I didnt see any " flapper " of any kind.

Did someone mention the " clear " hose switch over to see IF water is flowing? Thats what the book says, and shows. This test at IDLE, though.
 
Re: Old OMC Buick Overheating

corsair23 said:
When I took apart my Risers to clean and repair last fall, I didnt see any " flapper " of any kind.
Click to expand...

yeah, you cant see them - you have to stick a long screwdriver down the exhaust port of the intermediate- then pull the screwdriver out and you'll hear a dull thud as they spring shut
 
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