I have a 71 Mercruiser MR-1 with GM 165 4.1. Restored boat complete, New Bellows Hoses Lower water pump belt and thermo. Cooling is good at half throttle. When I put the hammer down about a min later it overheats. Checked the inlet hose (hot as hell at this point) let sit and idle gets cool hose, even can throttle up and gets cooler even sooner. Can run at high RPM sitting there no overheat. Took lower drive off put the garden hose on eng side all is clear also same for lower unit all clear. Any ideas???
