over heat

[Phrancus]

checklist:
impeller wrong type?, just a little smaller and it will not have the flow it should produce
impeller gasket missing and thus not fitting as well as the old one?
replaced it with the old impeller to check if that works? If so: found the issue

connections: reverse the flow as mentioned: with air or waterpressure to check for leaks and blockage. Sucking in air from a leak?
any gaskets, O-rings, damaged? Clamps that cut into the hose?

pump itself: if it's worn and tired, it may have failed when fiddling with it by pulling off the impeller. So maybe just bad luck and it's lost its power to turn the impeller fast enough. Don't know how to check that hardware but surely someone here does.

you write that it doesn't suck, is that sure or can it be the output that is blocked so it can't get rid of the pumped fluid through? simple to test by taking a hose of elsewhere.

Whatever you do: your bilge is going to get cleaner

[Midnightsun]

Just thought of something I have seen mentioned in the past. Have you tried revving the engine to get it to prime more easily? Have seen others mention they needed to do this after an impeller change.

[tomschauer]

I always have to goose my throttles a bit at spring launch or whenever replacing impeller's to pull the water to the pump. They are then good for the rest of the season.

[pepmyster]

Thanks for all the responses, I did rev it up. nada.

[Phrancus]

I hope it's something small that afterwards sounds too simple to be true.

The other day I checked a few things on the SB engine. Made sure everything was ready, cleaned up, tools out of the way, rags in a bag. Ready for a test.

And then I started the port engine......

Still can't imagine how stupid that was. Especially the almost a minute that I was staring at the dials and realising something was wrong but not seeing what...!


I filled the suction tube with a hose, closed the strainer top quickly and though the water level dropped, I felt confident that water would reach the impeller fast enough. A smaller amount of air to work away before the pump starts to do its job. Perhaps your construction allows for that trick too.

[plittle2005]

I presume you have FWC engines, which hose water will cool when unloaded only. (Do not exceed idle rpm's) This tells you nothing about loaded operation.

You obviously have SOMETHING preventing raw water flow (also check AF level) so the best procedure would be to start with the pickup connections and open up each component and inspect for blockages (oil & gear coolers, main heat exchanger, hose linings, elbows & risers ) serially. Then if the raw water circuit looks good, check for blockage in the AF tubes in the main cooler.Have the elbows & risers been replaced within the last 5 years? Could be a rust flake mass has broken loose. If 5 years old, best replace them now, when the system is opened up you can inspect much more effectively.

Have faith...you already have checked some parts, you know the system configuration, you KNOW that it's gotta work if assembled correctly and is clear of debris! The linear step-by-step method will eventually find it!

Good Luck!

[pepmyster]

Closed cooling engines.

[tomschauer]

I would have to get back in there and look at the pump housing. If your gasket or O ring, didn't seat properly or if you cracked the housing or bent the cover, any vacuum leak will prevent the pump from pulling the water.

[pepmyster]

True. Opened and checked, all Looked good. Is there a VP procedure for bleeding after replacement?

[tomschauer]

Sounds like a head scratcher.

Sit back have a beer and think about what may have changed. There should be no bleeding on the raw water side.
Maybe pop off the off the hose after the raw water pump where it goes into the heat exchanger. If it spews water, then the pump is good, either way you have narrowed it down to either the pump of after the pump.