MerCruiser I/O 2.5 Over heating

[Duke of ....]

Oops!! I had stated this as a reply so now I am posting it. lol New B

My over heating is at slower speeds. When I increase the RPM's the guage comes down to mid range. When coming back to the dock at slower speeds the guage gets almost to 190.

The boat sat for about 3 years so this might be some help with your answer.

Should I just put a good coolent in it or open the water pump for a look see.

Thanks for any help you may have for this problem.

Duke of ....

 

[chiefalen]

Re: MerCruiser I/O 2.5 Over heating

If it were my boat i would put in a new impeller, t-stat, and full tune up.

Change the out drive oil, motor oil.

Then i would post the results after you run it on the water.

And i would buy a manual before i start work.

Good luck!

 

[JustJason]

Re: MerCruiser I/O 2.5 Over heating

low rpm overheating is a sign of a very worn water impeller (the pump in the drive, not the one on the engine) or the water impeller pumping in air as well as water. The latter of which could be a number of things.

Think of it this way.... the pump is engine driven, at low rpm your pump is not delivering enough volume/pressure of water to cool the engine.
at high rpm the volume/pressure goes up enough to cool the engine.

CheifAlen's got it right.... start at the impeller and work your way up.

 

[Bondo]

Re: MerCruiser I/O 2.5 Over heating

The boat sat for about 3 years so this might be some help with your answer.

Ayuh,... I agree,...

The Impeller is the place to start...

 

[Duke of ....]

Re: MerCruiser I/O 2.5 Over heating

Many thanks to all three of you guys. I am going to buy a repair manual and have a go at it. I'll let you know how I make out.

Thanks again,
Duke ....

 

[achris]

Re: MerCruiser I/O 2.5 Over heating

Please don't buy a seloc or clymer.... You'll just be back here with questions to clarify the manual... Buy the Merc genuine article....

Chris..........