omc cobra 4.3 overheating problem !!!!!

[vmax-6]

Needing Help on a cooling problem on my 1993 OMC Cobra 4.3 as it is over heating problem only! at idle up to 2500 rpm, when the muffs are on at home there is no problem. It has a new impellor KIT; I have checked all hoses and pwr. steering heat exchanger no blockage anywhere!! The Y pipe flappers are both working great. Took the boat on the lake, I hooked up a hose to my flush tee inline from leg water pump to thermostat housing, with the hose over the edge of the boat at idle it was spitting sporadic became better at higher rpm but still sporadic,I thought this would be a steady flow of lake water. My t stat works properly I took it out and tested it in the kitchen.any thoughts would be appreciated.

 

[a70eliminator]

Re: omc cobra 4.3 overheating problem !!!!!

You say it has a new impeller kit, so what did the old impeller look like, was it desintigrated pieces missing anything like that, cause it only takes a little piece of rubber the old impeller to plug up the orifice in the pump.

 

[vmax-6]

Re: omc cobra 4.3 overheating problem !!!!!

The impeller was melted had the leg in a tub to try to figure out the overheating problem instead of putting the boat in the lake ,not realizing that the water level needed to be above the water pump .The water pump only melted no chunks out of it at all! Can you explain where the orifice is as I have destroyed one in the past and I back flushed from the engine and removed any pieces from the pwr steering oil cooler ( and yes there was some pieces there) but this was not the case this time.Thanks for your quick response this problem is driving me crazy.

 

[a70eliminator]

Re: omc cobra 4.3 overheating problem !!!!!

Well I'm not sure if I'm saying this right but there are some small passages in the upper gear housing that can get junk in them, I cleaned out mine when I had it apart to change the shift cable and it had junk in it like mud looking corrosion, R&R is quite involved and I wouldn't be able to talk you through it for i've done it only once myself, although there is a vent tube off the impeller housing that can get plugged it's easy to check, do you not have a manual? If not this forum is the next best thing, although OMC topic don't live long unless it's a bashing.

 

[chiefalen]

Re: omc cobra 4.3 overheating problem !!!!!

Do you have a engine mounted water pump? That could get clogged up.

Did you last time check the long hose from the outdrive to the t-stat?

When was the last time you pulled the risers, this problem may have nothing to do with the impeller melting. Risers get clogged from rust. Manifolds also.

 

[danond]

Re: omc cobra 4.3 overheating problem !!!!!

Pull all the hoses off your engine. Drain the whole thing. I found pieces of an old thermostat in the bottom of one of my hoses.

Take another look at your impeller. Did you re-assemble it correctly, with the fins in the right direction? Is the impeller housing leaking? Mine was distorted from the previous owner constantly running it dry and it worked like crap. Leaked like crazy. I replaced the whole thing, housing, gaskets and all.

 

[vmax-6]

Re: omc cobra 4.3 overheating problem !!!!!

Thanks guys for the advice I will take any. Boat has external water pump in leg.
Just came from a water test, took the hose off inside the transom at the bottom had very little water coming from there when its running, noticed bubbles coming from under the water pump??? It has a new gasket and oring
It looks flat. The vent hole is clear in the housing and I blew air through that vent house going down into bottom of leg. It seems like its getting air but we had it in the water over the water pump is it possible there is a leak in the bottom inside of leg or the round face that?s behind the water pump? This is defiantly a leg problem