Hot water temp
 

I have a 2000 500hp efi...This past weekend went for a long run, about 90 min. non stop @ 48mph (3500rpm)...when we arrived at our destination we had to idle in about 10 min. to get to the dock.. the high water temp alarm went off, as you can imagine this went overwell with the wife....Shut the engine down and restarted all seamed well, still ready hot, but no alarm.

On the return trip it did the same thing, while running at cruising speed temp would maintain around 190, then shoot up when we idle....
I live in the north east, so are lake temps are still cold in the 50's...

Any ideas?


Thank You

Re: Hot water temp
 

Probably the impeller.

Re: Hot water temp
 

start wiht the raw water impeller and go from there.

Re: Hot water temp
 

Thanks for the feedback, Is there more than one water pump?

I will pull the pump apart tonight and check the impellar...

Re: Hot water temp
 

There is a raw water pump and a circulating pump, the circ pump is the one on the front of the engine the raw water is the one on the bottom left corner as veiwed from the front of the engine. The raw water pump is the area of concern, you need to check the housing as well as the actuall impeller. It is easist just to pull the whole pump and bracket off and pull it apart on the bench, just make sure you mark the hoses for reasambaly, put a zip tie around the top one and remeber or write down where the one with the ziptie goes.

Re: Hot water temp
 

Pulled the raw water pump and the impeller looks good....it must be the circulating pump...Do you have to replace the entire pump assembly or can you replace the impeller...


Thank for the help...especially labeling the two hoses on the raw water pump.

Re: Hot water temp
 

Ussuall the circ pump will cuase a high speed overheat not low speed. I think I understood that it didn't overheat till you backed off is that right ? Did the impeller have a set to it ? They can "look" good but actually be bypassing water.

Re: Hot water temp
 

Hillbilly, your correct it is a low speed overheat, the raw water pump impeller look good to me, however may have missed something...What is a set?

Thanks Again

Re: Hot water temp
 

Look at the impeller and turn the pulley. Do the blades flex and stay in contact with the housing?? If they do not then replace the impeller. I replace them every other year unless I burn one up before that. Only happen once but that was too many times.

Re: Hot water temp
 

CR 190 deg. is still to hot,my 2000 502efi temp runs around 155 deg. all the time,mercury manual calls for 142 deg. thermostat. either your impeller is bad or you have a blockage somewhere, do you boat in shallow water?

Re: Hot water temp
 

An impeller had taken a set when the vanes no longer hold tension against the housing when the impeller is new the vanes are straight and over time they loose there ridgitity and allow water to bypass around them. Also take a good look at the housing, if it has grooves or the endplate is worn this will also cuase water to bypass.