GT-40 getting hot at idle

[jedgell]

I have a '95 SN w/GT-40 and have had some cooling issues that last couple weeks. The boat runs at 160 while pulling a skier through the course and at idle between passes. The problem starts when I let it sit between sets for 10-15 minutes. When I start it up and idle the temp slowly, but steadily, climbs to 200. As soon as I take off the temp quickly drops back to 160. Last night it actually got a little over 200. And during the set, even between passes when idling its fine, it just seems to do this after the engine has been off for a few minutes. I just replaced the impeller last month, so not sure what could be causing this. I also checked the strainer and it was tight, and clean, and that was replaced last year. Any suggestions would be appreciated, thanks!

[richard]

Idle hot

I suppose the output of the raw pump not enough on idling, if you can find some way to increase the RPM of the raw pump on idling,the problem will solve,
Seconly,I'll change the thermostate to 140 degree.

[M3Fan]

RE: Idle hot

How's your voltage? Your temp readings will be high with low voltage. Right after a start, maybe you have a dip in voltage until you rev it up. Just throwing it out there.

[richard]

RE: Idle hot

M3Fan raise a good point, Touch the elbow and compare the temp. with your finger when idling or crusing, if not so different,M3Fan may right, otherwise,my point my refer.

[surroundsound64]

RE: Idle hot

Sounds like it's an impeller problem, but usually if the impeller craps out the temp with shoot up fast when the boat is idleing.

Check out what M3 said

[jos]

RE: Idle hot

On my new an first CCSN 1991 I have the same, it is running OK. 160 steady when iddeling between the passes 180max. Quickly down to 160 after pulling again.
Engine off, it rises, waterlevel in the engine below tempsender?, or heat accumulation out of the 600punds of iron, rises the temp without circulation, is this a known effect?
Hows your oil pressure? 20mph sets the press moderate, 30mph effects lower pressure, 40mph even lower. Oil is getting very thin as it is my conclusion. After totaly cool off the pressure is back on normal. Is this a known effect?

[jedgell]

RE: Idle hot

I'll check the voltage issue, what's the best way to check? Just curious, how does low voltage affect the temp at idle? Also, when I do start it up after its been running it starts around 180 (which I've experienced since I've owned the boat) and within 1 minute its up to 200, or a little above. But the weirdest part is that I let it idle for 5 minutes after my last set, and it was fine 160-162 deg. Then 15 minutes later when I started it back up to load up the temp rised to 200 quickly until I gave it some gas, to about 2500-3000 RPMs, then it drops to normal.

[TRBenj]

Re: RE: Idle hot

Just curious, how does low voltage affect the temp at idle?

I believe that M3fan is suggesting the possibility of your gauge not getting enough voltage at idle after restarting. Once the alternator charges the battery a bit, your voltage will return and your gauge will go back to normal.

It is also possible that you arent getting enough water flow at idle, and the increase in RPM's is neccessary to increase the flow. It is strange that it only has this issue after restarting warm though- I would think the symptoms would be the same when slowing down after cruising. I had this issue due to the strainer being slightly loose, but you said you already checked that.

Any chance your old impeller destroyed itself and there could be bits lodged in your coolant passages?

[SGY]

RE: Re: RE: Idle hot

My experience is that if the motor doesn't cool at idle, its probably the impeller.

[AirJeff]

RE: Re: RE: Idle hot

PJ just had this problem (hot at idle and normal while cruising) and his system was drawing some air in from the strainer. I've had similar problems, the strainers don't seem to seal the best all the time. You could also have one of your hoses loose, so you could check the hose clamps between the intake and the raw water pump.

[Nowakepc]

GT-40 getting hot

Sounds like its sucking air someplace. A friend had problem with 90 SN. Changed a lot of things finally noticed a few drops of water coming from trans cooler. A new cooler corrected the problem.