5.8L omc getting hot help

[Eute]

I have a 5.8L omc getting hot and i have check everything i can think of.
1) i checked the impeller...good
2) i checked the thermostat...good
3) i took the heat exchanger off blew through all the openings.... no obstructions
4) i blew through the hose going down to out-drive from impeller... no problem
5) i tried the 2 hoses going to the exhaust manifolds and they were pretty hard to blow though
Is this normal with the exhaust mans?
i have not considered the water pump on motor cuz in my experience if its not leaking from weep hole its still good

 

[etech2008]

Re: 5.8L omc getting hot help

Hello first of all the water pump on the motor will be bad without leaking out of the weap hull. Crab the pully and check for play in it. If necassary pull of take back plate off and visually inspect.

From what you have told me I would first and formost pressure test the block to check for blown head gasket. (That motor was good at that) If a pressure tester is not available to you you can get a block tester for chaep at any autopart store. It consists of a tube that goes into heat excahger and comes with a chemical that changes color with exaust entering the system these tests in my ipinion are not as accurate as the pressure test.

And last but not least "The redneck method" take the radiator cap off with the engine completly cold start it and see if coolent flies out. It works sometimes.

So to some it up pressure test it.

 

[jerryjerry05]

Re: 5.8L omc getting hot help

If the manifolds are original. An 89 is about due for manifols and risers.
Try to remove the bellows on the risers and check the conditon of the exhaust ports(where the water comes out).The risers/manifolds will get all kinds of crap built up in them and restrict the flow.J

 

[a70eliminator]

Re: 5.8L omc getting hot help

You should be able to through the exhaust manifolds with little resistance, they are probably scaled up, is this a closed cooling system you mention heat exchanger, I'm not too familiar with those, never had one.

 

[Eute]

Re: 5.8L omc getting hot help

i hooked a water hose up to the exhaust manifolds and the starboard side water flows though pretty good but on the other side it is spraying around the bellow after the elbow like there is a blockage in the down pipe to the transom. wonder what could be blocking that ? isn't that just a strait open pipe all the way out? that looks like a 2 1/2 to 3" pipe thats a awful lot of scale if thats what it is.

 

[haulnazz15]

Re: 5.8L omc getting hot help

Could have an exhaust flapper blocking the passage. I don't know OMC's exhaust details though.

 

[studdy05]

Re: 5.8L omc getting hot help

I have seen them fully clogged before but that could just as well be water bouncing off the exhaust flapper from the way you describe it.

If you pull the exhaust manifolds you can descale them for the most part by using Muratic acid from the hardware store that is used to clean bricks.

But more to the point, how do you know the impeller is good? Did you do a flow test? "Getting hot" when you crank it is something totally different than getting hot under load and high RPM.

Also, grease the swivel housing really good - if the seals go in the swivel housing or you lack grease there you can have exhaust gases recirculate back into your engine.

99 times in 100 I would think rebuild the sea water pump on any OMC stringer before another issue pops in my head.

 

[Eute]

Re: 5.8L omc getting hot help

doesnt get hot for about 3-5 min at idle and will get hot fast a high RPM, about 2 min i took the impeller in to get a new one and the mech told me no need that that was a pretty new one barely any wear. so PO must have had this issue before selling me the boat... as usual he didnt mention the over heating, i love honest people
i started noticeing all the new hoses and clapms as i got into this... go figure, along with a new thermostat.

 

[Eute]

Re: 5.8L omc getting hot help

i pulled the exhaust elbow and found that it is severely stopped up with rust and it has a crack looks like i got to flush the manifold also.

 

[studdy05]

Re: 5.8L omc getting hot help

Well make sure the rubber bellows it attached to isn't cracked. When they over heat and are old they tend to become untrustworthy and brittle. Look it over real close.

 

[Eute]

Re: 5.8L omc getting hot help

will do, thanks studdy