4.3 OMC Cobra overheat problem

[monty240]

I have a 4.3 OMC Cobra and i seem to have a problem with the engine getting any cooling water. I replaced the waterpump in the outdrive, (impeller,gaskets, housing) but still have inadequate water cooling the engine on or off the water. If I really compress the muffs when its out of the water and have the hose turned up I get plenty of water flowing through the engine and its fine but other than that the water pump doesn't seem to be getting the water to the engine. Please Help.

 

[Gary H NC]

Re: 4.3 OMC Cobra overheat problem

Sounds like something is very restricted.
Was the old impeller still in one piece?
Did the overheat problem start before you changed the impeller?
When you have it on the muffs does water leak out around the impeller housing?

 

[javsam]

Re: 4.3 OMC Cobra overheat problem

did you replace the stainless steel plate that the impeller rides against?.If there are scratches on the plate,you'll lose water pressure. the plate is symetrical,so you could just flip it around.

 

[monty240]

Re: 4.3 OMC Cobra overheat problem

Yes, the old impeller was still in one piece, the overheat started before I changed the impeller, and no water leaks out the impeller housing, I changed the ss plate that the impeller rides on too. just seems to get no water out of the pumpto the engine. Is there anything between the impeller and the raw water pickup that could be broken of disconnected?

 

[Gary H NC]

Re: 4.3 OMC Cobra overheat problem

There is a seal between the upper and lower half inside the drive.It is a water passage to the impeller.

diagram of your drive..

http://www.dougrussell.com

 

[DHPMARINE]

Re: 4.3 OMC Cobra overheat problem

I didn't see a year listed but it really doesn't matter too much.

Keep in mind that you may be pumping plenty of water into the engine,but if it can't get out,it stays in and just heats up.

You have to look at your manifolds,and elbows,as well as the block.

DHP

 

[monty240]

Re: 4.3 OMC Cobra overheat problem

its a 1991. I am getting no water at all to the thermostat housing. I disconnected it and there is nothing. the water doesn't seem to get to the impeller. If I take off the waterpump and hook up the muffs I still get no water getting to the impeller. I read in another post that it could be a plastic water tube guide. Could it be so simple as to be that?????

 

[marunr]

Re: 4.3 OMC Cobra overheat problem


If you pull the outdrive you can run water through a hose in to the plastic water tube guide. You'll probably have to remove the pivot housing to get it out if you need to. The hose clamp is nearly impossible to loosen without doing that. At least you should be able to force water up to the t-stat through that tube and see if it's clear.


If that is clear you might suspect the seal Gary H mentioned.

 

[Gary H NC]

Re: 4.3 OMC Cobra overheat problem

When its hooked up to the muffs are you getting water back out the exhaust?