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MCBoatGirl
09-16-2013, 02:15 PM
Hello,

I am looking for some advice. I have a 1991 Prostar 190. It is overheating when the engine is just in gear but no gas. If I give it some gas and get water running through it the temp goes immediately down within the normal range.

Here is what has been done so far:
Attempt 1: put in new impeller - old one did have bits that came off in nickel and dime size pieces. Checked hoses. Didn't see anymore visible bits. That did not solve it.
Attempt 2: Replaced thermostat this weekend with new marine thermostat. Still overheating in idle.

Any additional suggestions? Thank you!

Kweisner
09-16-2013, 02:25 PM
It sounds (to me) like you still may have some flow restrictions because and once your pump spins up a bit faster, it's enough to overcome the issue. I don't know your engine, but if it has a transmission cooler, then perhaps there's some residual blockage there that could be cleared.

MCBoatGirl
09-16-2013, 02:56 PM
It's a Ford 351.

thatsmrmastercraft
09-16-2013, 03:15 PM
Have you checked if the transmission cooler inlet screen is clogged?

MCBoatGirl
09-16-2013, 03:24 PM
No, but I will. I appreciate any and all help - thank you!

thatsmrmastercraft
09-16-2013, 03:27 PM
If there isn't any debris at the trans cooler inlet, I would go back to trying to find impeller debris. You might do some work backflushing trying to get the pieces moving that way.

Table Rocker
09-16-2013, 03:39 PM
Make sure you have a gasket on the front of your raw water pump and check for suction leaks between the raw water pump and the intake fitting in the bilge. The fact that the problem goes away with higher RPMs makes me think it might be sucking a little air at idle.

johnnye23
09-17-2013, 05:50 AM
I chased the same issue on my 79 S@S ,temp would rise to 195 degrees at idle . New impeller etc etc, finally bit the bullet and purchased a new RWP from Skidim. Boat has never gone over 160 degrees since installation.

MCBoatGirl
09-17-2013, 07:43 AM
Can you explain what RWP stands for? This is my first boat and engine I have worked on. Thank you!

MikeyOrange88
09-17-2013, 07:50 AM
Raw Water Pump. This is the pump that pulls the water into the system thru the hull fitting and pumps it up into the motor. There is also a circulating water pump bolted onto the front of the engine, just like an auto engine.

CruisinGA
09-17-2013, 07:50 AM
raw water pump. The pump that is driven by the crank pulley or belt, houses the impeller and pumps water from under the boat into the engine.

The circulating water pump is essentially the same (different seal) as the water pump on an automotive engine, and only moves water through the engine.