Conventional Wisdom on Rubber Impellers

[Jim Marshall]

Everyone tells me you should replace impellers every year. In my Glastron/Ford/Volvo I didn't know that for twenty six years and during that time only replaced one impeller. The boat would sit in the water six months of the year. The pump is a Jabsco and it sits above water line.

SO, MY QUESTION IS WHY REPLACE IMPELLERS SO OFTEN? I realize I may bring down the wrath of conventional wisdom.

Jim

 

[achris]

Re: Conventional Wisdom on Rubber Impellers

An engine mounted Japsco pump is a very different animal to a conventional pump inside the drive. Generally the annual replacement of impeller is more an issue of cheap insurance than a necessity to replace. I replace the impeller in my Merc Gen II about every 5-7 years, and even then it doesn't look like it really needs it.... Even the Gen I pumps I've seen at 5 years old without any problems. Not that I would recommend it....

The Japsco I would check every 4-5 years. The Merc Gen II check every 3-4 years and the Gen I I check bi-annually, if the user is not a sand dredge....

Chris.........

 

[Jim Marshall]

Re: Conventional Wisdom on Rubber Impellers

achris,

That sounds more reasonable. I think the time the one gave out the impeller had locked up in the body. I opened it up and it was a mass of rubber pieces. When I remembered I would loosen the bolts on the back to release the pressure. If there was some kind of lubricant that would not have swelled the impellers I would do so.

My dad was in the water well and pump business. We occasionally would run across a Jabsco Water Puppy which he called "Junk". They do self-prime and hold it, however.

Impellers and gaskets for the old Glastron are hard to find and costly, too.

Jim

 

[achris]

Re: Conventional Wisdom on Rubber Impellers

achris,

That sounds more reasonable. I think the time the one gave out the impeller had locked up in the body. I opened it up and it was a mass of rubber pieces. When I remembered I would loosen the bolts on the back to release the pressure. If there was some kind of lubricant that would not have swelled the impellers I would do so.

My dad was in the water well and pump business. We occasionally would run across a Jabsco Water Puppy which he called "Junk". They do self-prime and hold it, however.

Impellers and gaskets for the old Glastron are hard to find and costly, too.

Jim

I had a Water Puppy as a bilge pump in my first boat, and loved it.... Far from junk, I have never seen a pump anywhere near as good....

One of the problems with impeller that come apart (and the reason most people want them changed before it happens) is the bits end up in the engine cooling system and can (DO!) cause major headaches. Like blocking up thermostats or exhaust passages that are narrow...

Chris.......

 

[Jim Marshall]

Re: Conventional Wisdom on Rubber Impellers

We were dealing with pumps that would run for years, probably six to ten hours per day. They were simple impeller pumps with ceramic/carbon seals, which the Jabsco has as well.

In all fairness to the Jabsco, the brass impellers in jet and submersible pumps do not contact the case. At one to two thousand hours per year the Water Puppies just couldn't hack it. In a boat or in a bilge they do just fine.

I could see why those little rubber pieces could cause damage. I always fire the engine up at the first of the year with the muffs. The first thing I always do when I start the engine is go back and feel the cover on the pump. Being cool is a good sign. I do this even when the boat has been sitting in the water for a while.

I did notice one thing that was interesting. I replaced the sealed bearings that were separated by a bushing. The bearings were a loose press fit. The bearings were held in the housing by a snap ring but the shaft with a hit could move through the bearings. I guess it doesn't.

Jim