1989 4.3 overheating

[ready4lake]

I have a 1989 bayliner with a 4.3 omc engine and cobra outdrive. I recently installed a rebuilt engine from a local boat owner. I had it on the lake yesterday and watched the temperature guage as I always do. After 10 minutes of cruising the engine was smoking hot. I opened the engine cover and felt the exhaust manifolds which were still cool enough to touch but the rest of the engine was burning up. I shut it down and paddled back to the ramp.

I just started the engine today on muffs and it is still giving the same results. Checked intake pump and impeller was good. It is brand new by the way. Checked water flow to the thermostat housing and all was good. I also pulled the outdrive to check for blockage in the exhuast but there was a good flow of water with the hose connected straight to intake hose.

I pullled the thermostat and heated it up and it is fully open at 155-160 according to my temp gun.

I pulled the circulator pump and there is no play in the shaft and blades look good with no corrosion, but it is pretty old so I am going to order a new one. I will also get a new thermostat since they are cheap.

It seems that there is some blockage in the engine block or somewhere in the engine because everything else is flowing as it should. Is there anything that I am missing here? It has become a real head scratcher.

 

[britisher]

Re: 1989 4.3 overheating

No expert but I've read several threads here about impellers breaking up and the broken parts then moving around the water channels and creating the likelihood of blockages. Have you checked the hoses? Sometimes they can look OK on the outside, but have collapsed internally. It's an easy check to do. You could also do an engine flush, which I believe would be done via the thermostat housing after removing the TStat first. Good luck

 

[ready4lake]

Re: 1989 4.3 overheating

Well I think I have figured it out. I just removed all of the cooling parts from the block and ran pressurized water through the block. It was not making its way up to the intake. I think that the intake gaskets have been put on backwards(with the blocked ports in the front instead of rear). I will have to pull the intake manifold tonight after work and find out. I will keep you posted.

 

[ready4lake]

Re: 1989 4.3 overheating

I found the problem. The intake gaskets were backwards.:facepalm:

 

[Maclin]

Re: 1989 4.3 overheating

Yay! Thanks for posting the solution, very valuable to future iBoats searchers!