"run dry" impellers

[Kasanti]

I cross referenced and ordered name brand (Globe) "run dry" impellers for my Volvo d1-40 auxiliaries and Fischer Panda genset (all small Johnson pumps) as an experiment.

I have OEM spares as well.

My boat spends most of it's time out of the water and is only splashed when we want to use it. That means the pumps have to run dry for a short time when we splash and I have had some difficulty with wear. Enough that I might consider just replacing the three impellers as a matter of course when I splash.

Has anyone had experience with these Globe brand run dry's? If so, what are your thoughts?

Second, the raw water seal spring has failed as well from time to time. I am going to try some sort of fresh water flush and drain as experiment number 2.

Has anyone tried this before? Would it help to blow out the pump cavity with compressed air? Then rely on the "run dry" impeller to prime effectively?

There are two ways to do this layup: cover off and cover on. Cover off would mean a rinse and blow, lubricating the impeller - OK. Cover on would mean run fresh water through an let it set.

Thanks for your thoughts, and I am just looking towards the wisdom of those who have been around longer than me to "have a good cruise" and reduce my workload :-).

[Kasanti]

I found thread "500 Hr Globe Dry Run Impellor" after posting. "dry run" has a different connotation for me than "run dry" :-)

Still would like YOUR thoughts if you have any!

[Emmalina]

Would not removing them be easier when you haul out ?

[PUDDLE JUMPER II]

Yes... I've used these little buggers for 10 years... Worth their weight in gold... I change them out every two years as a part of my maintenance routine-- and save the old ones as HOT SPARES or Free Give-aways. They do not look worn in any way shape or form...

Personal preference and budget for sure-- I just love things well engineered. You have to appreciate the bloke that went to the trouble of using a better material to .make these impellers.

Cheers....

[HeywoodJ]

Originally Posted by Kasanti

..Second, the raw water seal spring has failed as well from time to time. I am going to try some sort of fresh water flush and drain as experiment number 2....

The seals are industry standard seals and the garter springs are not made of anything particularly corrosion resistant. Failure of the springs in sea water use is not unusual, and I would expect it would be even worse when stored damp (exposed to oxygen while still wet with salt water). A fresh water rinse might help, but it would have to get into the nooks and crannies.

The common solution is to replace the spring with an o-ring, finding one that provides the right tension can be a bit of a challenge. Option B is to take the seal to a good bearing shop and see if you can source a seal with a corrosion resistant spring.

[Kasanti]

Originally Posted by Emmalina

Would not removing them be easier when you haul out ?

That may be what I'll wind up doing. Would give me a chance to blow the pump out with compressed air. Unfortunately due to the locations of the pumps access is anything but "easy" :-).

[skipperpete]

Originally Posted by Kasanti

I found thread "500 Hr Globe Dry Run Impellor" after posting. "dry run" has a different connotation for me than "run dry" :-)



Still would like YOUR thoughts if you have any!

Your main engines could live without the Globe impellers but your generator will benefit enormously from using them. A 60HZ 2 pole generator spins at 3600 rpm and the raw water pump runs at half that rpm but the problem is that your FP genset goes from zero to 3,600 in the blink of an eye.... no idle, and no time to check the overboard for water flow so the tiny traditional impeller may run dry at high speed so unless it’s fully primed at startup it’s life will not be long. Many larger yacht builders put the generators above the sea level and with those raw water pumps it’s a very real problem.

[capt jgw]

I've tried Globe impellers on three different engines and never had one that would actually pump water. I put the regular black impellers back in and they worked fine each time. Maybe they work in a brand new pump, but on mine with some wear on them they did not. Apparently would not seal against the pump walls. Nothing but the regular black ones for me!

[Kasanti]

Originally Posted by skipperpete

Your main engines could live without the Globe impellers but your generator will benefit enormously from using them. A 60HZ 2 pole generator spins at 3600 rpm and the raw water pump runs at half that rpm but the problem is that your FP genset goes from zero to 3,600 in the blink of an eye.... no idle, and no time to check the overboard for water flow so the tiny traditional impeller may run dry at high speed so unless it’s fully primed at startup it’s life will not be long. Many larger yacht builders put the generators above the sea level and with those raw water pumps it’s a very real problem.

Excellent point, and yes more issues with the genset than the auxiliaries.

[skipperpete]

I agree, Globe impellers aren't for everyone and they do take a while to settle in. if your engine runs for hundreds of hours on the traditional impellers, stay with em.