Wingnutt
Petty Officer 1st Class
- Joined
- Jul 16, 2003
- Messages
- 255
The last time I had my Regal out, I noticed that after idling for any length of time (mainly trolling) my 89 Mercruser 4.3 / Alpha 1 will run quite warm. If I up the RPMs to about 1500 she cools right off to her normal operating temp. On plane, everything is fine; drop down to idle speed and the temp starts working it's way up again.
I don't have numbers on the temp gage, but with a 143 degree thermostat (replaced about two years ago) normal operating temp on the gage is about almost 1/2 way across the gage. After idling along for about ten minutes or so the temp creeps up to about 3/4 of the way towards the hot side.
A non-technical troubleshooting session went something like this. I can put my hand on the risers for about 10-15 seconds before it becomes uncomfortable, no knocking when accelerating, no excessive heat off the engine or excessive steam out the exhaust. She's just running a tad warm at idle. Oh yea, one more little bit of info, the boat is raw water cooled and has always been operated in fresh water.
After searching, there seems to be two possible causes. The impeller (age unknown, but at least seven years old) or the thermostat. Since the risers are relatively cool, I'm ruling them out for now. Sooooo with all of that out of the way, would it make sense to replace the impeller first, then check the thermostat?
I don't have numbers on the temp gage, but with a 143 degree thermostat (replaced about two years ago) normal operating temp on the gage is about almost 1/2 way across the gage. After idling along for about ten minutes or so the temp creeps up to about 3/4 of the way towards the hot side.
A non-technical troubleshooting session went something like this. I can put my hand on the risers for about 10-15 seconds before it becomes uncomfortable, no knocking when accelerating, no excessive heat off the engine or excessive steam out the exhaust. She's just running a tad warm at idle. Oh yea, one more little bit of info, the boat is raw water cooled and has always been operated in fresh water.
After searching, there seems to be two possible causes. The impeller (age unknown, but at least seven years old) or the thermostat. Since the risers are relatively cool, I'm ruling them out for now. Sooooo with all of that out of the way, would it make sense to replace the impeller first, then check the thermostat?
