Engine temp at idle

[rexmitchell]

De-winterized the boat the other day, changed the oil. Took it out to the lake and boat runs like a champ, seems to be running a bit faster than when I stored it in November. Had a quick question about my engine temp while at idle. Boat runs a cool 150-155 while moving, I was at the dock waiting to pick up a passenger in the water for maybe 5-10 minutes and naturally my engine temp went up to around 180 or so before we were back under way again. The temp didn't go up until about the 5 min. mark. My question is how much is the engine temp expected to go up while idling like this? It didn't get to the point of overheating by any means but is this normal? its a mercruiser 5.7 350

Thanks Rex

 

[Bondo]

Re: Engine temp at idle

Ayuh,.. When was the Impeller last changed,..??

I idle All day trolling,+ Never see temps that high...
160? to maybe 170? with a 160? T-Stat....

 

[Don S]

Re: Engine temp at idle

You are at the first stage of overheating. You know something is wrong, just not sure what.
When was the last time the impeller in the raw water pump was replaced? If the vanes are all bent over, hard and won't straighten out, then you aren't pumping very much water at lower rpm. Thus the higher temps.

 

[rexmitchell]

Re: Engine temp at idle

Ayuh,.. When was the Impeller last changed,..??

I idle All day trolling,+ Never see temps that high...
160? to maybe 170? with a 160? T-Stat....

As soon as the boat was in gear the temp dropped back down to normal within what seemed like seconds.

You are at the first stage of overheating. You know something is wrong, just not sure what.
When was the last time the impeller in the raw water pump was replaced? If the vanes are all bent over, hard and won't straighten out, then you aren't pumping very much water at lower rpm. Thus the higher temps.

Impeller is on my to do list this summer, maybe sooner than I was planning on doing it. I figured it was a problem there I just didn't know if it was normal for the engine temp to rise at idle. I ride motorcycles and my bike will run 176 all day long but at a stop light will get to 218 before the radiator fans even kick on, just how its designed. Wasn't sure if boats were the same. Thanks for the input.

 

[Don S]

Re: Engine temp at idle

Impellers are a regular preventive maintenance item, usually done every other year during winterization. Since you should have the drive off to check the ujoints, alignment, gimbal bearing and checking the bellows for water. As long as the drive is off, it's a great time to change the gear lube also. Just to make sure there is no water in it. While drained, that's a perfect time to seperate the drive halves and replace the impeller.
Not half way through the summer season when it overheats and damages other things first.

 

[rexmitchell]

Re: Engine temp at idle

Impellers are a regular preventive maintenance item, usually done every other year during winterization. Since you should have the drive off to check the ujoints, alignment, gimbal bearing and checking the bellows for water. As long as the drive is off, it's a great time to change the gear lube also. Just to make sure there is no water in it. While drained, that's a perfect time to seperate the drive halves and replace the impeller.
Not half way through the summer season when it overheats and damages other things first.

Gotcha, I replaced the gear lube with the impeller on my last boat too. I am going to take it out again this week and watch the temp a little more closer, but still replace in the next couple of weeks. Thanks