I have a 2008 mercruiser 4.3 carb/alpha 1 combo. It was purchased new in 2008. Ever since brand new the boat has shown 175 degrees at normal operating temp. The needle never moved once it went there. I never thought anything of it since that is right in the middle of the gauge. The risers have always felt normal to me also, but I have not checked temp.
At the end of last season I noticed the temp gauge would be around 175 as usual but after a long cruise it would just nudge a little past 175, maybe 2-3 degrees. It had been 2 seasons so I thought it was time to change the impeller. I changed it over the winter when I did all the rest of my maintenance. The old one looked fine, no missing pieces.
We took the boat out for the first time yesterday. Everything was great on the muffs in the driveway before we left. The boat is still doing the same thing as before. It stays at 175 on the gauge and at idle the risers feel cool. After a 30-minute cruise around 3000 rpm the gauge is maybe 2-3 degrees over 175 as it was last season but the risers are way too hot to put my hand on. Let it idle for a few minutes, gauge is back at 175 and the risers cool down.
After much searching on the forum it seems that I might have a volume problem due to an air leak or sealing problem on the drive? I wanted to see if maybe the thermostat was bad also. It seems I have a 160 degree thermostat and through many posts it seems most people's boats run in the 160 degree range. Thats when I started wondering if the 175 that my boat has always run is even normal?
This is only freshwater, 3rd season with the boat so I don't think I have corrosion problems or any issues like that. This is my first impeller change and there were no missing pieces to clog anything. Am I being paranoid or is this the start of an overheat problem? What else to check? I will try to get an actual riser temp next time out. Should a thermostat with only 2 seasons need replacing?
At the end of last season I noticed the temp gauge would be around 175 as usual but after a long cruise it would just nudge a little past 175, maybe 2-3 degrees. It had been 2 seasons so I thought it was time to change the impeller. I changed it over the winter when I did all the rest of my maintenance. The old one looked fine, no missing pieces.
We took the boat out for the first time yesterday. Everything was great on the muffs in the driveway before we left. The boat is still doing the same thing as before. It stays at 175 on the gauge and at idle the risers feel cool. After a 30-minute cruise around 3000 rpm the gauge is maybe 2-3 degrees over 175 as it was last season but the risers are way too hot to put my hand on. Let it idle for a few minutes, gauge is back at 175 and the risers cool down.
After much searching on the forum it seems that I might have a volume problem due to an air leak or sealing problem on the drive? I wanted to see if maybe the thermostat was bad also. It seems I have a 160 degree thermostat and through many posts it seems most people's boats run in the 160 degree range. Thats when I started wondering if the 175 that my boat has always run is even normal?
This is only freshwater, 3rd season with the boat so I don't think I have corrosion problems or any issues like that. This is my first impeller change and there were no missing pieces to clog anything. Am I being paranoid or is this the start of an overheat problem? What else to check? I will try to get an actual riser temp next time out. Should a thermostat with only 2 seasons need replacing?
