Stumped on overheat problem

[mc1920]

I have an 89 sunbird 22' , which is overheating at high rpm, its ok at low, but rises quickly.<br /><br />ok, I replaced the thermostat, engine water pump, both manifolds, and cleaned out the elbows, also checked the impellar.<br /><br />when at high rpm for a very short time even the inlet hose gets hot.<br /><br />ready to burn it. please advise <br /><br />Mike <br />mc1920@aol.com

 

[mc1920]

Re: Stumped on overheat problem

sorry, Its a 5.0 cobra, omc od, salt water cooled

 

[crazy charlie]

Re: Stumped on overheat problem

Mike if you took the time and trouble to check the impeller you should have changed the entire kit.Housing,wearplate impeller etc.How did the thermostat housing look on the inside.They corrode from the inside and restrict the flow.Did you check the exhaust flappers .Charlie

 

[f_inscreenname]

Re: Stumped on overheat problem

Make sure your hoses are not getting kinked or bent to hard. What type of thermostat did you replace it with? You didn't get it at the local auto parts store did you. What was your temp before replacement? Did you replace with same thermostat (you were running at 160 so you replaced with a 160 stat ). Mine uses a 140 thermostat and runs at 160 (175 after running hard). Everything in boat new from water pick up to exhaust (even the motor) set like from the factory. If I run a 160 thermostat, after a run it would jump up to 190 to 200. Got proper stat and problem solved. <br />After every thing you have done I would definitely change the impeller. If it is weak it will not have the same force (water pressure) as a new one and at higher rpm’s you need lots of flow.

 

[mc1920]

Re: Stumped on overheat problem

Thanks for the help,<br /><br />Its out of the water once again, and I did a test with the gallon jug on one of the hoses coming from the thermostat housing to the port side manifold before I took it out, it idles @ 1000 rpm and the flow looked good, but when I took off the pipe the exaust came out the inlet water hose if u know what i mean, Is this to do with theflapper valves? how do I check those?<br /><br />Also I managed 1800 -2000 rpm for 20 min and temp never moved??<br /><br />Thanks again

 

[Boomyal]

Re: Stumped on overheat problem

Are you saying that you disconnected the hose from the Tstat housing tree to the exh manifold water jacket? and exhaust came out of that hose, from the tsat housing? or back from the exh manifold? The flapper valves shouldn't have anything to do with sending exhaust back thru the cooling system.<br />If you were up to tstat opening temperature and you had exhuast back from the tstat tower I would suspect a blown head gasket. That would definitely cause overheating.