1991 454 sport concept omc king cobra

[wandarer]

Can anybody help with an over heating problem It overheated and I did not notice until it quit.I replaced the impellor and noticed a few pieces missing one fairly large one ,drove it again and at high rpm the temp goes up to 200, slow it down and it goes to 145.I pulled the thermostat housing and I am not sure if the thermostat comes out or is it rusted in there. I boiled the housing and the thermostat seemed to be opening . how do I back flush the system to maybe unclug a piece of the rubber from the impellor that maybe in the engine. or is the something that I am missing here?

 

[HT32BSX115]

Re: 1991 454 sport concept omc king cobra

Howdy,


The raw water from the transom (and raw water pump) should go to the power steering and engine oil coolers before going to the heat exchanger (if closed cooled) or thermostat housing.

Most oil coolers and some PS coolers have tiny little tubes in them that will not pass impeller fragments.

You'll have to remove both to clear them of the fragments from that and possibly previous impeller failures.


The other obstructions to flow can include the heads, block, intake and exhaust manifolds and risers.

If it's a fresh water engine the block, manifolds and risers don't clog (with rust) very quickly (years). In salt water the manifolds and/or risers can clog in a few short years or so.....

They usually clog (you hope) before they rust though


You'll probably find impeller fragments in the oil/PS coolers and/or associated hoses.



Cheers,


Rick

 

[wandarer]

Re: 1991 454 sport concept omc king cobra

Thanks for the advise I will try that.
If I were to use pressurized water and back wash the coolers without removing them would I damage the integrity of the coolers.
Your saying by removing them you could look and see if there are any obstructions!

 

[zbnutcase]

Re: 1991 454 sport concept omc king cobra

Sometimes the pieces will wedge in the cooler and wont come out by backflushing, you have to use a pick to pull them out, easy when removed

 

[wandarer]

Re: 1991 454 sport concept omc king cobra

Hay there Rick
Thanks for all the tips, there were no pieces in the power steering cooler, with the size of the holes I dont think anything could get by that point .
Back to the thermostat ! Does the thermostat come out of that housing or is it one piece

 

[Bondo]

Re: 1991 454 sport concept omc king cobra

Does the thermostat come out of that housing

Yes,.....

 

[a70eliminator]

Re: 1991 454 sport concept omc king cobra

And the spring part goes towards the engine.

 

[wandarer]

Re: 1991 454 sport concept omc king cobra

thanks again for al you suggestions !
I spoke to another mechanic and he suggested to remove the stat and make an alum plate in place of the stat with a 5/8 hole in it and that should solve the problem

 

[a70eliminator]

Re: 1991 454 sport concept omc king cobra

Well, good luck with that!

 

[wandarer]

Re: 1991 454 sport concept omc king cobra

well ,I tried that plate with the hole in it, and the temp stayed at 145 at about 3000rpm but any higher rpm and the temp started to rise again. So I removed the plate all together and it did the same thing . So I started over at the impellor, removed it , had a good look at the impellor housing and noticed that the steel housing inside the plastic housing had spun and was only pumping about 60% of its capacity. so I am off to get a new kit housing and impellor. with any luck my problems will be over!