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mercury 150 blck max motor overheating

powerman_270

New member
i have a 18 stratos with a 88 mercury black max motor...it runs good less than half throttle but once i open it up and drive it a lil ways the temp guage gets climbing real fast...then i have to shut her down before shes to hot....what do you think would make this happen?
i was thinking either a impeller or thermostat
anyone else have the same problem?
 
Did you look at the tell-tale stream and see if it's still shooting water at high rpm? Problem exists when the impeller key is slipping at high rpm or the impeller itself is too hard and has the tips of the impeller fins worn off. If water is still shooting steadily and strong, your motor oil is either undermixed or it's having clogged thermal stats in which the water skips the block and comes right back out the exhaust. In this case the tell-tale hose does not having water either or it does, it's loose and catch water from the exhaust pipe.
Good luck.
 
i never checkd if it was shooting water out at high rmp's i know it shoots water out but not like it use to ...i think your right about the impeller fins being worn off...
thank you
 
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