4.3 chev OMC gets hot over 35mph

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philbilly

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Joined
Jun 23, 2009
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1
Our chevy 4.3 OMC cobra heats up if I run at 35mph or over. I then have to let it idle or drive slow to cool it back down.
The impeller is 2 years old. The manifolds dont seem hot to the touch....Where do I begin to look for the problem?
(freshwater boat)
 
Bt Doctur

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,111
Re: 4.3 chev OMC gets hot over 35mph

1 Impeller change
2 Thermostat check/replace
3 clogged/clogging riser.
 
bustermin

bustermin

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Apr 13, 2009
Messages
315
Re: 4.3 chev OMC gets hot over 35mph

it sounds like your impeller/water pump it beginning to fail, it is pumping enough water to cool at lower speeds because it does not need as much water to keep it kool, at higher speeds the impeller if not straightening out enough to pump enough water thru the sytem. i would change the impeller/water pump and the thermostat.
 
180shabah

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: 4.3 chev OMC gets hot over 35mph

Where do I begin to look for the problem?
Click to expand...

Either slow down, or replace the impeller. It should be done every year anyway.
 
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