I know this is the topic of many other threads, but I've been through them all with no luck in finding my particular issue. That said, here is my problem. This spring I changed the impeller for preventative maintenance reasons (no overheating issues prior to this) and since then my engine runs at 170 while idling, but as I increase the RPMs (while underway) the temp gauge climbs to about 200. As soon as i drop back to an idle, the temp almost immediately returns to back down to 170 - sometimes dropping to 140 and slowly moving back up to 170. No alarms are going off either. I also don't remember the engine idling at 170 in previous years - I think it was more like 160.
What I've tried so far:
Looking for pieces of the old impeller - the old impeller came out in tact.
Clogged inlet - Plenty of water coming to the thermostat housing - I measured 2.5 gallons in 15 seconds coming out of the fuel cooler pipe which is where the outlet side of the sea water pump's hose connects to.
Air being introduced int the system - I've attached a clear hose between the end of my fuel cooler and the thermostat housing, ran the boat at all rpms (while underway) and noticed no air bubbles coming through.
Clogged manifolds/risers - I took off the starboard side riser and inspected - looked fairly clean - some corrosion but not enough to block any of the 4 passage ways by more than 10% if that much. Also, while underway the temps on both risers stay at about 105 - measured with an IR gun. I can certainly hold my hand on them with no problem. Due to the visual inspection and low temps I decided not to pull off the port riser at this time.
Thermostat - replaced and still have the same result.
Actual temperature of the engine - while underway I took many readings with an IR gun - averaged around 165 - highest was 175 back on the center of the intake manifold. The thermostat housing and area around the temp sensor read around 160.
Temperature sending unit - replaced and there was no change in the condition.
Where do I go from here? Can my gauge actually be malfunctioning in the way described? Is there a way to test the water pump on the engine?
Any help is appreciated - thanks for reading...
Joe
What I've tried so far:
Looking for pieces of the old impeller - the old impeller came out in tact.
Clogged inlet - Plenty of water coming to the thermostat housing - I measured 2.5 gallons in 15 seconds coming out of the fuel cooler pipe which is where the outlet side of the sea water pump's hose connects to.
Air being introduced int the system - I've attached a clear hose between the end of my fuel cooler and the thermostat housing, ran the boat at all rpms (while underway) and noticed no air bubbles coming through.
Clogged manifolds/risers - I took off the starboard side riser and inspected - looked fairly clean - some corrosion but not enough to block any of the 4 passage ways by more than 10% if that much. Also, while underway the temps on both risers stay at about 105 - measured with an IR gun. I can certainly hold my hand on them with no problem. Due to the visual inspection and low temps I decided not to pull off the port riser at this time.
Thermostat - replaced and still have the same result.
Actual temperature of the engine - while underway I took many readings with an IR gun - averaged around 165 - highest was 175 back on the center of the intake manifold. The thermostat housing and area around the temp sensor read around 160.
Temperature sending unit - replaced and there was no change in the condition.
Where do I go from here? Can my gauge actually be malfunctioning in the way described? Is there a way to test the water pump on the engine?
Any help is appreciated - thanks for reading...
Joe
