Overheating intermittently at idle

[Elanor]

2010 cobalt 230WSS
5.7 GI-J
DPS A195 drive

Boat will run normal 1 day then next time out will overheat while idling out.
Replaced thermostat. New water pump and impeller.
Old impeller was not in bad shape or missing any pieces.
While testing it overheated after 3 or fourth start.
Removed supply line to thermostat housing and no water coming in.
Disconnected hoses and water runs thru all hoses and out thru the transom our the inlets with no apparent obstructions.
Any suggestions???
If it is sucking air somewhere, would that stop water pump from sucking any water?

[AsLan7]

2010 cobalt 230WSS
5.7 GI-J
DPS A195 drive

Boat will run normal 1 day then next time out will overheat while idling out.
Replaced thermostat. New water pump and impeller.
Old impeller was not in bad shape or missing any pieces.
While testing it overheated after 3 or fourth start.
Removed supply line to thermostat housing and no water coming in.
Disconnected hoses and water runs thru all hoses and out thru the transom our the inlets with no apparent obstructions.
Any suggestions???
If it is sucking air somewhere, would that stop water pump from sucking any water?

.
Hey Eleanor. Thanks for coming out of the woodwork after 2+ years!

To answer your question, it could be sucking air somewhere. Mine was doing that thru the fitting on the transom but would only manifest itself at higher rpm's.

Yours seems to be at low rpm's which normally means a physical obstruction somewhere. What does your gauge read? Mine would overheat and the alarm would come on around 175+ degrees which would then put the engine into limp mode. Does yours have any of these symptoms? Just trying to rule out a bad sensor as well if you have good water-flow.

Mine documented here.

Oh, and any pictures of your 230WSS?

Officially, welcome aboard mate!

.

[Elanor]

Both digital and anologue gauge get up above 200. Temps gets above 160 and keeps climbing. Fuel pump starts whining cause it’s getting hot. I can hear impeller start squeaking for lack of water I believe. After it’s gotten above 200 fuel pump appears to be vapor locking assume because it’s hot as well. Weird thing is it doesn’t do it all the time.

[Big Block Power]

Ok. Will it over heat if you run it off the garden house fitting in the engine compartment. Sounds like you have a water supply issue from the drive to the impeller.

[cmattj]

Ok. Will it over heat if you run it off the garden house fitting in the engine compartment. Sounds like you have a water supply issue from the drive to the impeller.

Yes.. time to give it a new source of water. Have you had any work done recently to the outdrive?

[Elanor]

No work to out drive but a lower unit fluid change

[cmattj]

No work to out drive but a lower unit fluid change

Ok. Reason as at idle or even in gear idle is the lowest source of pressure. 1.0 lb to 20lb if pressure from idle to 3500 rpm.
As Bbp said let’s run her on the trailer and determine a different source, and see what comes out the drive.
It may be time to get into the pickup system as it could be a flapper or pinched.