3.7 gets hot while idling

ROY WILLIAMS

Petty Officer 1st Class
Joined
Aug 8, 2022
Messages
394
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

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,394
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?
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,883
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.
 
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