Overheating Where Do I start

I have a 88 Wellcraft with a 4.3 GM motor it appears I just bought. First time I took it out busted the lower unit and a boat repair guy who was a friend of who I got boat from rebuilt lower unit. After changing fuel filters and oil decided I was going to take her out. after 5 min of running WOT at about 4500 rpm noticed temp gauged jumped to 240. Shut her down on water still had dog house off and the as alot of cracklin/poping and smoke and I thought I was in trouble. Got it back to house- exhaust manifolds were steaming hot but no burnt wires or anything unusual I could see, let her cool off a few hours and checked and there was no thermostat. Put on boot, water comng out of little hole on lower unit started it up and with 5 minutes of idling with one rev up temp went from 140 to 200. Im new to boats and know just enough about cars to be dangerous...Could this be a bad waterpump by chance or something else.

Re: Overheating Where Do I start

first i would check that your exhaust manifolds are working properly and make sure you have a thermostat in. also, when was the last time the impeller was changed, i would check into that one also

Good luck

Re: Overheating Where Do I start

Stupid question--- how do i verify that? This is where I dont clearly understand is how the whole cooling system works in a boat.

I need to verify but I think it was changed when I had the lower unit rebuilt.. I know Gibler bearing was replaced.

Tired and cant spell tonight

Re: Overheating Where Do I start

not sure of your last question, are you wondering how to check the manifolds?

Re: Overheating Where Do I start

Yes-- I understand car motors in general and how normal cooling systems works but not sure how it works in a boat- I had lower unit rebuilt with new seals and new gibler bearing would the mechanic have seen impeller doing this? He is friend of a friend that is supposed to been trustworthy.

Re: Overheating Where Do I start

yes he would have seen the impeller as it is in the lower unit, but that doesnt mean it was replaced, also i would remove the vent covers on the lower part of the stern drive to make sure they are clear and not plugged as that is where the water picks up the from, i would remove the run water throught the manifolds to make sure you are getting water in through them, remove one of the hoses and poor water into it and make sure you it comes out the other end.

Re: Overheating Where Do I start

Went back this morning as sure as anything the thermostat was up top bulit in to the top part with no easy way to remove and rusted where it would not open--- will fix it later and post results--- thanks for assitance.

Re: Overheating Where Do I start

gshldon said:

yes he would have seen the impeller as it is in the lower unit, but that doesnt mean it was replaced

Click to expand...

Not sure how you can say that with such certainty, so far it has not even been mentioned what kind of outdrive it is.
It may not have a raw water pump in the outdrive.

UpdateRe: Overheating Where Do I start

UpdateRe: Overheating Where Do I start

Checked with guy the worked on it he did not replace impeller. I went to local shop and bought a kit for $50.00 pulled three screws and replaceed the whole thing in about 15 minutues. Removed old thermostat put everytrhing back togeher and running across lake the temputure stayed down until I sat idle while i checking everthing and it creeped up to about 200 - went in gear and it dropped rather quickly.

Next I noticed new problem I was taken on a considerable amount of water and everything was dripping wet inside. Got my bro in law in boat and realized when I start accelerating a large amount of water was shooting out like a water faucet. After checking all connections traced it down to a canister with two water lines and to brass fittings. Pulled this off and it appears it some type of transmission cooler and the leak is coming out of canister on one side where its fitted on and you can see some corrosion around it.....

What am i looking at now for something like this... Out drive is a Cobra OMC


What is this part called... as Im trying to determine cost

Re: Overheating Where Do I start

power steering cooler

Re: Overheating Where Do I start

Thanks to everyone for the help - now i need to locate a part number... making progress thou.

Re: Overheating Where Do I start

do u use anti freeze? then you would have a close system. and the leak could be gthe heat exchanger.
you dont indicate where you are from , but for sure you should take your boat to a shop and learn how to winterize it properly in the fall, less you not drain it correctly.

Re: Overheating Where Do I start

If the cooler you are talking about is around 8 to 10" long, remove it, take it to a radiator shop and have it resoldered. Many times the ends corrode or freeze crack an leak. Resoldered they work fine for many more years.

Re: Overheating Where Do I start

Thanks-- I got the part off the boat and where it connects on the cone of the whole piece on the side its leaking there is stress - I will take it to the radiator shop next week and see if the can seal it back up rather than purhasing a new one. I was able to locate the -part # 985840 and this is the same I have.

Re: Overheating Where Do I start

wajajaja02 said:

do u use anti freeze? then you would have a close system. and the leak could be gthe heat exchanger.
you dont indicate where you are from , but for sure you should take your boat to a shop and learn how to winterize it properly in the fall, less you not drain it correctly.

Click to expand...

In Texas and this boat I just purchased through a friend of a friend for a good price-- hence all the project work to get it going. This is my second boat and last year learned how to winterize a boat properly.

Thanks again for the assitance.