Have a pair of 96' 150hp V6 mercs (carbed), both run warmer than I'm comfortable with under throttle over 2000 rpm's. Both run cooler at idle. Both have entirely new water pumps (housing/gaskets/impellers) less than 16 months old (and this is the reason I put them in, they have always done this). Took to dealer a while back for maintenance and asked to check temp while there. Said all was OK, said as long as alarm does not go off it'll be fine. Engines run as hot as 175-180 F under full throttle, back down to 150 F or so at idle if you trust temp gages. Clymer manual says thermostat is 145 F and engines should not exceed 20 degrees above thermostat rating. Alarm never goes off, but I do exceed 165F. I've read the manual till my eyes cross, and the way I understand it.. is that the poppit valve takes over as the main temp controler under pressure (high RPM). What's your best guess at what might need looking into? or is all OK as the dealer said? One more thing, Clymer says to test the overheat alarm by grounding the tan/blue wire, it sounds when grounded, is that assurance enough it will work if it gets too hot??? All replies welcomed.
