Impeller Life

[Icarus]

Originally Posted by kmacdonald

My Kubota 25 HP has a Jabsco 29460-1631 water pump">raw water pump. I changed the first impeller at 1050 hours. A few blades were cracked but little wear on the blade tips. It still worked well. I just changed the impeller for the second time. It had 1080 hours on it. One blade was cracked and little wear on the tips. It was still working well. The pump was leaking from the weep holes so I replaced the seals in the pump. Impellers are Jabsco brand.

The Impeller on my 40hp Isuzu lasts about 3 years...however, I check it every year or before a voyage.
,

[Calif.Ted]

I've had 2 fail, one catastrophic after the intake blocked by kelp. The other was only 6 months old when I thought I detected a decrease in cooling water. Took it out and one vane had 2 large pieces gone. I'd guess it to be defective from manufacture or it was improperly stored or excessive age when I bought it.

[gonesail]

another trick i have seen but not tried .. is to compress the new impeller with a plastic wire tie .. enough to push it into the pump.

[Kiwi Dave]

Well - I waited too long (even worse I am not sure how long since last changed 2-3 years?).
Volvo D1-30 x 2
Although there was no overheating and seemingly good wet exhaust water flow. On removing the raw water impellers both had lost 2 vanes. The problem was then I had to find the missing vanes requiring hose removal and opening the inlet cover to the heat exchangers.
I had put replacement off as due to the instillation there is limited access to the raw water pumps. I have learnt my lesson - now will be changed every year. Volvo impellers do come with glycerin lubricant.

[Nineteen]

Originally Posted by gonesail

another trick i have seen but not tried .. is to compress the new impeller with a plastic wire tie .. enough to push it into the pump.

Works well. I have a 3JH3 with bugger all room and it helps. I also use DC-4 for lube as it doesn't dry out and will not effect the rubber.

[Finestkind]

Switched from plain rubber 15+ years ago for all the common reasons.
One Name - GLOBE - Good enough for the Coasties & outperformed my Yanmar impellers by a factor of 4!!
Look them up & don’t look back….

[capt jgw]

Originally Posted by Finestkind

Switched from plain rubber 15+ years ago for all the common reasons.
One Name - GLOBE - Good enough for the Coasties & outperformed my Yanmar impellers by a factor of 4!!
Look them up & don’t look back….

Actually I've had very bad luck with Globe impellers. Tried them in 4 different engines, not one of them would pump water. Went back to black rubber and they pumped fine. All four. I have no explanation as to why.

[Finestkind]

Sounds like a fitment problem…
Your mileage may vary. 8-)

[capt jgw]

Originally Posted by gonesail

another trick i have seen but not tried .. is to compress the new impeller with a plastic wire tie .. enough to push it into the pump.

That should work. On the monster big impeller for the fire pump I wouldn't have been able to compress it with a zip tie, wasn't easy even with a hose clamp.

[capt jgw]

Originally Posted by Finestkind

Sounds like a fitment problem…
Your mileage may vary. 8-)

Yeah I don't know. Two of them were the Oberdorfer pumps on Universal sailboat engines. Very common pump and the impellers were the part number Globe listed for that pump.

[wholybee]

Originally Posted by Finestkind

Switched from plain rubber 15+ years ago for all the common reasons.
One Name - GLOBE - Good enough for the Coasties & outperformed my Yanmar impellers by a factor of 4!!
Look them up & don’t look back….

How do you measure that? With a flow meter? Or by running them until the disintegrate?

[GrowleyMonster]

Low hours? Change it every year. It's the right thing to do. Also beware of impellers that have sat on a shelf for 20 years. I generally don't put 200 hours on an engine in a year, on a sailboat, but if I did motor a lot, I would not go longer than 250 to 400 hours or so. I usually keep one old one with no cracks, as a spare for the guy who didn't see the economic advantage in owning his very own brand new spare impeller. This is usually the guy who has never changed his, because it still pumps water. When I have some, I coat used spares with castor oil which does a good job of preserving rubber, even synthetic rubber, and keeping it supple. Right now I have I think 3 new spare impellers on hand, new, and no old ones because I gave my last changeout to Mr. Can't Be Bothered To Buy A Spare Impeller. So, it was a year in the pump, a few months in a zip lock with a coating of castor oil, maybe 200 hours of use, tops. It might keep him from having to spend $30 for another year. Or, it might fail catastrophically and clog up the heat exchanger with bits of rubber, tomorrow.

Also important is the state of wear in the pump itself. Especially the cam plate. They can chew up an impeller. An end cover can reduce pumping power when it gets badly worn and I have replaced my original with a stainless steel one that uses an O ring instead of a paper gasket. I now have a complete rebuilt spare raw water pump, too, in addition to impellers. These pumps can be surprisingly expensive, but worth rebuilding.

Jabsco, Oberdorfer, Sherwood, all basically the same in principle, all rebuildable, all using rubber impellers that need to be changed annually even if not used. You can make an end cover easily enough. Also I upgrade my end cover plate screws to socket head cap screws. Much easier to manipulate an allen wrench than a screwdriver in a tight engine compartment. You lose fewer screws, too.

[Finestkind]

Yanmar impellers showed hardening in 5 months & occas cracks twice (5 month season for me) Hardening is enough of a reason to change.
Went to globe & inspections were good - would change out just to be safe end of 4th season.
‘Bout 4 times the useful life for me. I don’t own stock….
Whatever works for you.

[MVDarlin]

If the boat is laid up for part of the year it may be wise to open the cover plate and spray some lube on the impellers and then run a thin shaft screwdriver around the tips before starting the enginge.

[SY Harmony]

When you accept the reality that; impellers are designed to fail from the moment you open the box. Life with them becomes more sane.
Keep spares, get proficient in swapping them.