Closed cooling overheating - solved

[Youghster]

In the interest of saving some fellow boater a trip "down a rabbit hole", I offer. My 1995 Santego 5.7 TBI had overheating problems, especially at idle in long no wake zones. After impellers (several), one new / rebuilt, raw water pump, professional heat exchanger cleaning, new thermostats - I finally got serious about pulling some hoses and troubleshooting. It appeared that the engine coolant circulating pump was weak (no noise, no leaks). So I hustled on down to Carquest and picked up a replacement for about $50 and a couple gallons of antifreeze. Port engine now rock steady at 170*. Starboard replacement pump is now in hand and going in ASAP. I hope this is helpful to somebody.

[Viper]

[km1125]

Curious if you did (or will) pull the back off the water pump to see what was going on. I heard of one where the impeller was coming loose on the shaft.

[pepmyster]

When I was working at Chrysler, I found once a water pump problem, over heat like the one your stating. All looked great, took off the water pump, and the impeller on the shaft was spinning free. Glad you found your problem!

[Jay Fusaro]

Well done!

[Youghster]

I did not pull the back off the old water pump - yet. All the guys on the dock are wondering too.

[Raven]

is the impeller in the water pump replaceable? or do you have to replace the whole assembly?
I am having the exact symptoms at idle( heat guage creeps up) but at higher rpm it cools down to normal

[km1125]

QR_BBPOST is the impeller in the water pump replaceable? or do you have to replace the whole assembly?
I am having the exact symptoms at idle( heat guage creeps up) but at higher rpm it cools down to normal

You might want to start a new thread for your issue, or you'll get confusing responses mixing up your issue with the OPs.

But -to answer your question- no circulating pump I've seen has a field-replaceable impeller. They are usually pressed on the shaft with a hydraulic press. But if you were referring to the raw water pump, then yes, those always have replaceable impellers.