Idles hot, cools off when running

[hawghead]

Started up my new to me boat and quickly the temp guage is reading real hot after idling in the slip for several minutes. Killed it and let her sit for a while fired it back up and the engine was still real warm, started under way and it cooled off to normal operating temp and when I got back to my dock at idle speed the temp was starting climb again.

Any thoughts? Runs at a fine temp when in gear and moving, heats up bigtime when idling. Just curious to your thoughts.

I have it in for a full outdrive service and they are going to look into it. Any thoughts of what to expect?

Thanks

 

[Bucks45]

Re: Idles hot, cools off when running

I'm fighting the same thing right now. The guys on here are alot of help. What setup do you have? That's where you're going to want to post this question.

 

[Chris1956]

Re: Idles hot, cools off when running

Mercruisers with bad water pump impellers do that.

 

[ENSIGN]

Re: Idles hot, cools off when running

Change the impeller while it's in the shop.

 

[CheapboatKev]

Re: Idles hot, cools off when running

Hawghead..
Post this question in the I/O forum..
Make sure you state what motor/drive system you are running or you will get put in the corner and get a time - out..lol

 

[hawghead]

Re: Idles hot, cools off when running

Sorry forgot the perinent info.

1986 Wellcraft sporting a Merc 350 Alpha 1.

 

[four winns 214]

Re: Idles hot, cools off when running

Runs at a fine temp when in gear and moving, heats up bigtime when idling......

Have you had work done on your drive? Had the same problem after the "experts" at the local Sea Ray dealer changed the impeller my Alpha 1. The kid they had doing the job simply did it incorrectly-- he didn't get the water tube positioned correctly during reassembly. Overheated at idle because of insufficient water flow, but cooled down when throttled up.

After the water tube was correctly positioned, end of problem.

 

[DJ]

Re: Idles hot, cools off when running

Moving to I/O section.

 

[grahamh]

Re: Idles hot, cools off when running

Your symptom is typical of a worn impeller, unless you've changed it recently, I'd start there.

 

[smarks]

Re: Idles hot, cools off when running

Have you had work done on your drive? Had the same problem after the "experts" at the local Sea Ray dealer changed the impeller my Alpha 1. The kid they had doing the job simply did it incorrectly-- he didn't get the water tube positioned correctly during reassembly. Overheated at idle because of insufficient water flow, but cooled down when throttled up.

After the water tube was correctly positioned, end of problem.

Sounds like a typical bad impeller
Regards
Steve

 

[hawghead]

Re: Idles hot, cools off when running

This is a new to me boat. The prior owner said he had the impeller replaced last year. Cant remember if he said he did it or if he said "that he had it done" Hopefully it's just the water hose issue, the tech at the Marina is going to investigate.

 

[Don S]

Re: Idles hot, cools off when running

This is a new to me boat. The prior owner said he had the impeller replaced last year.

It doesn't matter, CHECK the raw water pump impeller. It's the first thing you check with an IO overheat because there are so many things that can destroy one. Including a plastic trash bag in the water that the outdrive catches.

 

[nitrosteve]

Re: Idles hot, cools off when running

You might also check your belts to make sure they are all tight. A loose belt will do the same thing.

 

[hawghead]

Re: Idles hot, cools off when running

Roger that, I checked the belts they all seem fine, certainly not loose. Okie Dokie the impeller is the plan of attack.

 

[tschmidty]

Re: Idles hot, cools off when running

Someone posted an interesting thread from mercruiser on exactly how quickly the water pump is destroyed with no water flowing. Takes about 1 minute.

 

[Grand Larsony]

Re: Idles hot, cools off when running

BALL VALVES - search the forums

 

[PitchFork]

Re: Idles hot, cools off when running

I would check the check balls springs and stretch the springs out. I seem to have the problem after the springs have been in the Tstat housing for awhile. Stays at 140? while at anything above idle 1,000 RPM but while idle for more than a few minutes up to 180?+ alarm and only way to cure to rev to 1,200 RPM for a few minutes.

When I first bought my boat I was having the exact same problem so I took it to the shop to have the impeller changed and it had no affect on my overheating. But the housing was warped and missing pieces. After further review and searching I discovered the Tstat housing was missing the check balls.

Parts 3,4,5,8 Diagram

 

[Burtonair01]

Re: Idles hot, cools off when running

How often do you all change you're impeller? And is it an easy change on a Volvo duo prop?

 

[NateZ]

Re: Idles hot, cools off when running

Someone posted an interesting thread from mercruiser on exactly how quickly the water pump is destroyed with no water flowing. Takes about 1 minute.

I had one smoking in about 25 seconds. Forgot to hook up the water inlet tube, oopps.

Nate

 

[Burtonair01]

Re: Idles hot, cools off when running

Where is the impeller located?