No thermostat, overheating

[Galvez83]

Engine with overheating issue. 5.7GS The thermostat along with impeller replaced. The engine had an overheating event and it looks like things might not be very good over the horizon. I removed the 140 therm and engine will run at 175 at idle. All of this is on a hose hook up not via muffs. By the looks of it exhaust gases are present in the raw water coming up from the intake feeding the thermostat housing. Oil has no water ...yet. The question is, should my temp be that high without a thermostat on a hose?

 

[dypcdiver]

You are right to be surprised.
I had something similar, I put clear hoses from both T'stat outlets to the manifolds and could see hardly any water flow at 600 RPM however at 3000 RPM I could clearly see exhaust gas in the flow.
The water pickup tube in the lower outboard leg had been burnt through as it is located in the exhaust gas flow.

 

[Scott Danforth]

the issue without a thermostat, is the cooling water will not be correctly controlled and the motor will overheat. at a minimum, if you remove the thermostat, you need to run a restrictor plate.

replace the thermostat and look for the reason you have lack of flow

 

[Galvez83]

the issue without a thermostat, is the cooling water will not be correctly controlled and the motor will overheat. at a minimum, if you remove the thermostat, you need to run a restrictor plate.

replace the thermostat and look for the reason you have lack of flow

That is where i am coming up blank. I removed and replaced the impeller and replaced the impeller housing 2 times. Removed and cleared all the hoses. Removed, opened the back plate and re-installed the engine circulation pump. Flushed the engine for 20 minutes. Removed therm housing and ran it so water could bleed out the thermostat housing hopefully to flush any obtructions and nothing. The common denominator that i am seeing is that, once the hoses that feed the manifolds are removed from the thermostat housing the water coming out is sputtering. I had 3 trips to the mechanic already with no luck in determining the overheating.

 

[Scott Danforth]

check the raw water inlet fitting at the drive. they develop cracks over time and the pump can suck air.

 

[Lou C]

There are 3 things on this model that can cause this problem 2 are mentioned above and there’s one more; the water tube inside the drive has water grommets that can be partly melted by overheats.
On boats moored or docked in salt water you will get barnacles and other growth in the water intakes and eventually this will cause a low volume of raw water flow. On my Cobra I had this problem & had to split the drive to clean it all out. Also removed & tossed that water intake screen used in the Cobra drives this allows me to rod out the water intake holes with the boat on the mooring.

 

[Galvez83]

check the raw water inlet fitting at the drive. they develop cracks over time and the pump can suck air.

Boat has a thru hull cooling the PS and the impeller. Pump moves water to the engine at a decent level. Risers and manifolds are new as well. Thermostat is new as well 140°. It was removed and tested in hot water and it operates as it should. The hose feeding the thermostat housing is cool and moving water.

 

[kenny nunez]

There is a good chance you have a head gasket leak. Your first post mentions an overheat event. Since you are drawing water from a thru hull fitting rules out the drive incoming water.

 

[Scott Danforth]

was your hose supplying enough flow to the muffs? most residential hoses do not.

 

[ESGWheel]

was your hose supplying enough flow to the muffs? most residential hoses do not.

It overheats in the water as well.

Here is some more background on the OP’s issue link. My thoughts for the path forward is Dypcdiver’s suggestion in post 2 (clear hoses) followed be a compression test & leak down test as suggested in post 19 of the background link.

@Galvez83 > it seems like all other avenues have been ruled out, so down to the head gasket / warped heads.as you are suspecting.

 

[ptclabs.jp]

hmm you could always do it the old fashion way. remove the inlet to the pump run a hose into the water and see if it is still a problem. If not it is somewhere behind there. make sure you use a hose that cannot suck in on itself, wire sprung works well