Running hot but not overheating

[GoodGrief]

Merc 140 GM 4cyl out of the garage to ready for first fishing outing. Fired on the second try and ran like an old champ (1986) idled good but temp reached 175 then on the throttle lowered to normal 150ish. Back to idle temp climbed again. Water discharge looks about half of what it should be. Your thoughts?

 

[midcarolina]

I would say the first thing to do with any overheat condition is to replace the water pump impeller, higher temp at idle versus on the gas is a indication of a worn impeller........

 

[GoodGrief]

I have to ask if you're referring to the water pump on the motor versus the impeller in the prop?

 

[floatin radio]

In the outdrive (prop). Impeller is $15-20 whole housing kit is $45 or so. Couple hours to change if your mechanically inclined

Do yourself a favor and buy a service manual

 

[midcarolina]

in addition to getting a manual You can also check on you tube there are bunches of instructional video's on replacing outdrive impeller