83 Chrysler 75hp won't pump water at 2500 rpm'

[copmac]

The overheat buzzer goes off at 2500 rpm and I noticed no water pumping out of the motor. If I slow down to 2000 rpms or slower, water pumps out of the motor again. The buzzer will stop after @ 30 sec as long as I slowdown. I noticed all this after putting a new thermostat in and testing the boat tonight. I guess water should pump out at all times especially at higher rpms, right? Any ideas on why the water stops pumping out at 2500 rpms.

 

[roscoe]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

Impeller and possibly the waterpump housing are wearing out. Time to replace them.

 

[jrlogan11]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

I wouldn't run this engine until you replace the impeller and get this fixed. Unless of course, you prefer an engine that doesn't run at all!

 

[copmac]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

So far I put in a new thermostat, impeller and water pump housing. Water pumps out until I get to 2500 rpm then I don't see the water pumping out. So far I have fixed nothing. The buzzer still goes off because no water is coming out when i speed up over 3000 rpm and it over heats. What could it be now. Any clues?

 

[72INVADER90HP]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

your sheer key could be broken an your impeller or you did not put it on.

 

[copmac]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

So far I have tried a new thermostat, new impeller and new water pump housing. I think it must be something in the upper engine. Any ideas? What could keep water from pumping out once it reaches 2500 rpm?

 

[scotiany]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

Did you try going back to the old thermostat?

 

[copmac]

Re: 83 Chrysler 75hp won't pump water at 2500 rpm'

I believe I found the problem. The water pressure relief valve is stuck. I read the repair manual and it states that when this gets stuck it prevents additional cooling water from bypassing the thermostat and ciruculating through the water jacket. Which causes the engine to overheat at high rpms.