Had a 5hp Merc that ran hot too. Pulled the “water jacket” cylinder top cover as Merc has no head & poked, scraped & cleaned all water port passages & got it to cool, Yea, pull the powerhead but before find replacement base gasket I suggest. Water from pump runs through the exhaust cover plate via a baffle plate to keep water out of cylinders, then cools the cylinders & out. Does this motor have a weep hole for water exit Frank?
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