merc 150 opti overheating when @ less than 1500 rpm / nowake zone/ but will run ok @ 4200 rpm for an hour? engine pissing ok ,no obstruction @ least visible have flushed engine 2x's already what gives???
Perhaps a problem with the thermostats? The 'stats will only affect cooling at lower speeds, once underway the poppets will open and flow lots of water thru the powerhead.
