Mercruiser 4.3 l/x overheating (slightly)

[bobuk]

Hello,

while on tick over in neutral my engine remains at the bottom of the temperature scale. But when put into forward and sitting at 2000 RPM the temperature gradually creeps up to about half way. Reducing the revs brings the temperature down, and increasing the revs brings the temperature up but never much more than half way on the gauge. Any idea which pump or cooling part that could be at fault? Cheers in advance Bob

 

[bjcsc]

Re: Mercruiser 4.3 l/x overheating (slightly)

We need some numbers, Bob. We can't see your gauge...

 

[DHPMARINE]

Re: Mercruiser 4.3 l/x overheating (slightly)

What happens when underway?

I've never had occaision or reason to run at 2000RPM sitting for any lenghth of time.I think it might climb,because underway you have water pushing towards the drive intakes.Sitting you do not.

DHP

 

[bobuk]

Re: Mercruiser 4.3 l/x overheating (slightly)

I do mean when she's underway, the temperature does climb with speed. But at idle the temperature sits low on the guage. Underway and around 2200 RPM the temperature goes to about halfway (sorry no numbers on the guage). This is a recent thing as my other engine tends to sit at the bottom half of its guage.
Bob

 

[bigbrownbuku]

Re: Mercruiser 4.3 l/x overheating (slightly)

how long is a piece of string. does your guage have numbers?

 

[bjcsc]

Re: Mercruiser 4.3 l/x overheating (slightly)

Hmmm. So is this occurring in one engine on a dual engine boat? Did the one you are suspect of ever do anything different? My first inclination is that something is amiss as in my own experience, once my engine gets to temperature (150&deg), it stays there, regardless of RPM. I run ~2000RPM sometimes as depending on current or traffic I need it to maintain steerage. The only thing that changes are my EGT's, which run ~900&deg at idle and about 1350&deg cruising, water temp stays constant. If you knew what your thermostat opened at, and what temps your engine was getting to you may have a starting point. You may want to find Don S.'s cooling system check thread and run through it.