3.7 gets hot while idling

[ROY WILLIAMS]

Sorry about the late reply. It's a 89 3.7l. Alpha 1 out drive. 4 " heat exchanger. Son took a small video as I was running rv antifreeze trough it. (Overkill I know).

exchanger water ,,, distilled water 50% antifreeze coolant engine 50% ...
my MCM470 1978 engine ,,, exchanger distilled water 40 % 60% engine antifreeze ...

RV antifreeze, no?

 

[Scott Danforth]

Inspect the bellows every year when you pull the drive for the annual maintenance (check alignment, bellows, gimbal, and u-joints)

Does your 470 have the upgraded heat exchanger?

 

[RoadKingClassic]

Inspect the bellows every year when you pull the drive for the annual maintenance (check alignment, bellows, gimbal, and u-joints)

Does your 470 have the upgraded heat exchanger?

It has a 4 " heat exchanger

 

[racerone]

Inspect / clean the heat exchanger.

 

[tank1949]

Was out with my sons today in his boat with the 3.7 mercruiser. He bought of a buddy of mine who took good care of it. Changed impeller last year. It gets up in temp if you idle for too long. Today the water temp was 65 degrees. The engine was running warm. Then noticed she got up to 200 after idling for 15mins. I put it in gear and got it moving. It came down to 180 quick. Got it going faster around 3000 rpm and it came down to 160 fairly quick. Question . Is this normal for that motor to get hot if you just idle for that period?

salt water used? Inspect risers.