As seen in Speedboat Magazine’s May/June 2020 Issue.
525SC Overheating at Idle
I have a ’97 Fountain 42 with three 525SCs. It has been parked and not run for two years. When I started one of the engines on a hose, after about ten minutes the temp gauge went up to 140 then dropped back down to below 100 and the overheat alarm started going off. I have replaced both the thermostat and sea water pump. Water pressure is normal (compared to the other two engines) while running. I also installed a gauge where the alarm sender is located in the intake manifold and verified the temp is around 190 there and the water is in fact cold around the thermostat. I am not sure where to look now.
Santa Fe, TX