Odd 4.3 overheating

[Ryajohns]

Hello All,
I am having a overheating problem with my 06 mercruiser 4.3
Last season I was having a issue with the starboard riser running hot but the engine seem to run normal around 160. I replaced the starboard manifold thinking that was it. It was not I found the check ball was the issue I ordered a new check ball kit and a new thermostat and housing. I installed the new check ball kit and new housing + thermostat. Now Both risers run cold but the engine will get hot up to 190-200 then alarm then I cut it off I assume it would only continue to climb.

Things I have tried.
New impeller kit. (Alpha 1 gen 2) old one looked good no damage.
New water recirc pump
Swapped the old thermostat back into housing to see if the new one was defective. (New one now re-installed)
Tightened the check balls as tight as I could imagine they would need to be thinking it was a pressure issue. (risers still run cold).
Checked water flow from
Oil/powersteering coolers (good flow).

Note: when running the water does circulate through and come back out of stern exit ports.

Any ideas very much appreciated this one has me stumped!!

 

[Fun Times]

Did the high temp only seem to show up right after new T-housing and/or new check ball valve kit?

 

[Ryajohns]

Did the high temp only seem to show up right after new T-housing and/or new check ball valve kit?

Correct. but the hot riser issue went away.

 

[Fun Times]

Correct. but the hot riser issue went away.

Okay, Can you post your engine serial number and all the part numbers ordered and installed?

 

[Ryajohns]

Okay, Can you post your engine serial number and all the part numbers ordered and installed?

Engine serial number is unknown the tag is worn out

Thermostat housing- (Mercury Thermostat Housing - Fits MCM/MIE 4.3L, 5.0L, 5.7L Carbureted Engines w/ Dry Joint Exhaust - 864592T
SKU: 864592T) to be specific See below The T for the check ball screws in the top of the housing.
https://www.partsvu.com/housing-assy-864592t.html

Thermostat- (Mercury Marine/Mercruiser OEM 160 Degree Thermostat Kit, 807252T5)

Impeller- (Quicksilver 817275Q05)

Pump- (Quicksilver/Mercury 4.3L Circulating Pump 46-8M6005225)

 

[Ryajohns]

Pump

https://www.partsvu.com/water-pump-assy-46-8m6005225.html

 

[Ryajohns]

1

 

[QBhoy]

Hi. The most obvious thing that comes to mind right now, is around the idea that you may have slightly overheated a little the first time. If you did…you may have damaged and dislodged one or both of the exhaust flappers. This may result in one or both of them melting off and finding their way down the y pipe or further in the exhaust. Resulting in a blockage in flow if the cooling water.

 

[Ryajohns]

Update: Removed the thermostat now not overheating. Tested thermostat in boiling water with thermometer seems to open as designed. Any ideas?

 

[Fun Times]

Update: Removed the thermostat now not overheating. Tested thermostat in boiling water with thermometer seems to open as designed. Any ideas?

Thanks for posting the part numbers, just wanted to help ensure all seemed correct as sometimes there are different designed T/Housings with or without check valve systems that could affect temperatures.

When installing the base gasket between the housing and intake manifold, are you installing the gasket dry or with a sealant?
Needs to be dry so it doesn't affect the grounding of the sensors possibly giving out false reads to the gauge and warning horn alarm system... Using an infrared temperature gun helps ensure the engine is truly getting hot.

When installing thermostat, are you installing a cork type gasket (not rubber) up inside the housing first then the thermostat followed by a white plastic sleeve?
The correct orientation is videl sort of seen here because item number 7 goes in first, https://www.mercruiserparts.com/bam/subassembly/31492/11812/170

 

[Scott06]

Update: Removed the thermostat now not overheating. Tested thermostat in boiling water with thermometer seems to open as designed. Any ideas?

I suspect there is something wrong with check balls . Thinking they are allowing too much water to go directly to elbows and overboard. This starves the block of incoming raw water Coming up from the drive. Suspect removing thermostat reduced restriction feeding water into block circ pump. Somewhere there is too little restriction of water flow to elbows.

 

[Ryajohns]

Thanks for posting the part numbers, just wanted to help ensure all seemed correct as sometimes there are different designed T/Housings with or without check valve systems that could affect temperatures.

When installing the base gasket between the housing and intake manifold, are you installing the gasket dry or with a sealant?
Needs to be dry so it doesn't affect the grounding of the sensors possibly giving out false reads to the gauge and warning horn alarm system... Using an infrared temperature gun helps ensure the engine is truly getting hot.

When installing thermostat, are you installing a cork type gasket (not rubber) up inside the housing first then the thermostat followed by a white plastic sleeve?
The correct orientation is videl sort of seen here because item number 7 goes in first, https://www.mercruiserparts.com/bam/subassembly/31492/11812/170

I did use sealant on gasket from housing to motor and correct I did the cork gasket first then the thermostat then the retaining sleeve. I will say when thermostat is in I couldn’t touch the housing it was so hot but I will try the temp gun to give it a double check.

 

[j cat]

inspect the compression piston cylinders . could be a head gasket