Overheating at idle MCM 140 1978?

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Boatbudd

Cadet
Joined
Jun 30, 2012
Messages
18
I was trying to figure out how this cooling system works because it is overheating at idle. So far I have figured out (I think) that water comes in to the engine thru a smaller hose (about 1" ID) to a port near the thermostat. It seems to return thru the exhaust ?

I read somewhere about some check balls causing this problem? Any advice?? Thanks Bud
 
H

HT32BSX115

Supreme Mariner
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Dec 8, 2005
Messages
10,083
Re: Overheating at idle MCM 140 1978?

Boatbudd said:
I was trying to figure out how this cooling system works because it is overheating at idle. So far I have figured out (I think) that water comes in to the engine thru a smaller hose (about 1" ID) to a port near the thermostat. It seems to return thru the exhaust ?

I read somewhere about some check balls causing this problem? Any advice?? Thanks Bud
Click to expand...

Howdy,

You pretty much have it correct where the water comes from.


Marine engines overheating at idle are usually due to a defective raw water pump or clogged water supply hose/fittings (from raw water pump impeller fragments or other debris) Since the jacketed exhaust system also can clog and prevent the water from exiting, it can also result in the same type of overheating symptoms.

The checkballs are in the thermostat housing (V-6/8 engines) to equalize the water flow to the manifolds/risers.
 
Bt Doctur

Bt Doctur

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Aug 29, 2004
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19,111
Re: Overheating at idle MCM 140 1978?

cool1.jpg
 
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