Temperature rising at idle

J

jsmigielski

Cadet
Joined
Aug 1, 2011
Messages
9
I have an 86' sea ray and the temperature rises at idle and slow speeds. I can get the temperature to go down by accelerating and it holds steady at cruising speed. Any suggestions on where to start?
 
G

Grand Larsony

Petty Officer 1st Class
Joined
Aug 13, 2008
Messages
221
Re: Temperature rising at idle

Replace water impeller AND housing, check for any obstructions on intake (holes on side of IO unit), be sure not outflow obstructions (flapper in Y pipe), no kinked coolant hoses (especially the one from outdrive to thermostat housing).

When was service last done -- especially the impeller?
 
G

Grand Larsony

Petty Officer 1st Class
Joined
Aug 13, 2008
Messages
221
Re: Temperature rising at idle

Inspect and clean thermostat housing, replace t-stat while there.
 
Brentathon

Brentathon

Petty Officer 1st Class
Joined
Dec 29, 2009
Messages
385
Re: Temperature rising at idle

Which engine do you have?

I had a slow speed over heat years ago, and it was related to the highly corroded T-stat housing, that didn't allow the little white plastic "check balls" to properly seat. But that was on my raw water cooled 1990 5.7.
The check balls provide some back pressure, which keeps the coolant circuit topped-off, as well as helps to equalize the water that's divided to each of the exhaust elbows.
If they don't seat well, cold water from drive can exit to the elbows, bypassing the block.
 
greg82255

greg82255

Senior Chief Petty Officer
Joined
Oct 26, 2009
Messages
781
Re: Temperature rising at idle

The impeller is the first place to look in an overheating situation. Pull the lower and replace the impeller, and if you don't know when it was last done, might as well do the housing too. Make sure you use OEM parts. They're a little more expensive but most of the experts on these forums say they are worth it.
 
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