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Replaced EVERYTHING yet still overheats on one side

D

David Long

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"I have a 7.4 liter Mercruiser

"I have a 7.4 liter Mercruiser that overheated on the starboard side so bad in cooked the starboard exhaust bellows and the boat began to take on water. I replaced the bellows, exhaust manifold, circulating pump,impeller,thermostat. Put the boat back in the ocean and it still overheats on the starboard side only. Then I ran it on the hose/muffs and it appears that water is flowing from both side of the exhaust. Any ideas would be greatly appreciated.}"
 
"Ayuh,...

How can you tell


"Ayuh,...

How can you tell it's overheating on only 1 half of the motor,..??

Is there water exiting the starboard side exhaust tip,..??
Is there "Flow" from that side of the motor,..??
What'd the T-Stat housing look like,..??"
 
"...cooked the starboard e

"...cooked the starboard exhaust bellows and the boat began to take on water."

What about the exhaust shutter? Did it melt and fall down into the "Y" pipe? Or do you have thru hull exhaust? Riser elbow ok?
 
"THANKS so much for responding

"THANKS so much for responding, I have a infra red heat sensor that indicates the starboard side is running 15 - 20 degrees hotter than the port side and it keeps rising until I shut it down.

I also replaced the thermostat housing."
 
""""I replaced the

""""I replaced the bellows, exhaust manifold, circulating pump,impeller,thermostat. I also replaced the thermostat housing."""

What about the ELBOW/RISER?

That would be a very big restiction in outgoing water flow."
 
Thanks again for responding-I

Thanks again for responding-I have replaced elbow riser as well. I ran it for 1 hour at 2500 RPM's in a bucket. Using my infra red heat sensor and the starboard riser is 135 degrees and the port side is 108 degrees. And there was a 25 degree difference at the thermostat housing outlets to the manifolds as well. Any ideas would be greatly appreciated.
 
"Ayuh,.... I'm Sorry Dave,

"Ayuh,.... I'm Sorry Dave,....

You just Don't have a Problem.....

Riser Temps are just Never the same,...
It's just the nature of the Beasts.....
Your #s are Not out of line,... At All..."
 
"I've seen where GM has le

"I've seen where GM has left casting in the r.s. port of the water pump. It's always on the right side of the pump. The right side port in the water pump, on the engine, is usually completely blocked with casting material, not allowing proper flow to r.s. of the engine. You would have to remove the pump to find out for sure. (I've seen three of these pumps so far). I found this when at low rpm's, the engines did OK, but when you raised the rpm's, it would overheat, but only on the r.s. Since you already replaced the pump, then maybe inspect the flow in the head.???? Good luck."
 
"If you have replaced so much

"If you have replaced so much and still have this over temp issue then the problem is the incomming water supply. As said it is the nature of the beast as to where the coldest water goes.

BOTH elbows/risers should be very close to the same temps. This is raw fresh water directly thru the t housing and straight to the elbows.

You may have air turblance in the incomming water supply, If this boat has spent any time in salt water the incomming fresh water pass thru at the transom assembly may be restricted due to white oxidation growing around the hose and constricting it.

Just a couple of additional thoughts."
 
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