f100 yamaha overheating

muskrat

Chief Petty Officer
Joined
Apr 13, 2004
Messages
445
Motor overheats at higher speeds.Removed lower unit water pump & impeller looked ok,replaced any how.installed new thermostat looked pretty clean.Checked presure valve looked clean.Tell tale isnt strong but steady.Test run again still overheating at higher speed??????P.s.
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Not sure if that motor has a poppit valve or not but that would be where to look if it does.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Sounds like you did not put new water pump in only looked at it and put it back, I would replace with a complete kit and housing if there is any sign of melting of plastic housing.

After all of that has been done and still have problem you are left with cooling passages plugging.
Either take apart to clean or try some scale removing flush to clean it out
 
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