1990 5.7l mercruiser alpha 1 overheating

Diverdano

Recruit
Joined
Oct 6, 2019
Messages
1
Just bought boat and motor keeps overheating. Freshwater cooled. Had it at Mechanic’s multiple times. Had the leg off changed impeller checked risers, cleaned heat exchanger, just checked circulation pump, checked the whole cooling system and all is clean and clear of blockage. Any ideas? He is saying maybe cracked block, but it doesn’t make any sense as it’s a new rebuild?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,326
What was the original motor serial number?

When does it overheat, idle, mid range, WOT, all the above?

Was it a stock rebuild, use same parts or was more power added?

Does it have original HX or was this an add on?
 
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