On a recent trip after two days of flawless running, I noticed that the port 5.7l Mercruiser engine gauge was showing the water temp at 100. It would then sometimes go up and then go back down. They replaced the thermostat and then the thermostat housing. The problems still occurs. It is not the gauge because when the temperature drops the engine side of the hose on the thermostat cools right down. The engine temp goes up and down. At idle it seems to go up to normal temperature but when throttled up it drops immediately to cold? The mechanic says he is stumped.
