Engine running cold

S

Seba

Recruit
Joined
Aug 4, 2006
Messages
2
I have a Bayliner Capri 23ft. with a 7.4L MPI engine. The engine is always running cold. I tried to replace the thermostat and still runs cold. Once in a while I see the gauge moving a little bit over minimum but not much and it moves right back. Any suggestion where should I look?
Thanks.
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Engine running cold

This is a 7.4L V8 I/O. Temp gauges on those are not thermocouples but thermister operated just like your car. Temps should run 140 - 160. If you have a gauge calibrated cold-hot rather than in degrees its hard to tell if its accurate or not.
 
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billybones

Seaman
Joined
Jun 20, 2006
Messages
64
Re: Engine running cold

one last note to check, If the gauge runs on a red an white wire.( Known as a j type thermal couple). (red and yellow K type thermal couple.) Take a resistance reading before motor start. This should increase as motor temp comes up. Hope I am not out of place on this.
 
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billybones

Seaman
Joined
Jun 20, 2006
Messages
64
Re: Engine running cold

My experience with thermal gauges is they run on thermal wires.. If they rub raw that is where the temp is taken. They run on resistance.. so if they are exposed and shorted before the sender. you get that reading..This is a very low voltage situation. no blown fuses. Check your temp sender wires.. Does the motor feel cold? my experience is in cars, but assume it's near the same. I am sort of regurgitating. but not quite.
 
S

Seba

Recruit
Joined
Aug 4, 2006
Messages
2
Re: Engine running cold

One more note. Before all this started the engine was overheating due to bad seawater pump so I assume the gauge is good (it was showing the right temperature). As soon as I fixed the seawater pump the engine started to run cold.
 
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