Impeller Life

[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.

[wholybee]

How much time had elapsed between changes? They will fail with fewer hours and longer time between changes as well. I change mine annually, which would be much fewer than 1000 hours. Never any cracks. If there is a crack, it is about to fail and you changed it just in time.

[capt jgw]

Many people, myself included, change them annually regardless. The $40 tag is peanuts compared to a bad overheat. I'm on the Great Lakes where we're laid up 6 months of the year, it's on my winterizing/dewinterizing checklist.

[capt jgw]

Originally Posted by wholybee

How much time had elapsed between changes? They will fail with fewer hours and longer time between changes as well. I change mine annually, which would be much fewer than 1000 hours. Never any cracks. If there is a crack, it is about to fail and you changed it just in time.

Bingo. If they're cracked, you waited too long.

[thinwater]

Originally Posted by kmacdonald

My Kubota 25 HP has a Jabsco 29460-1631 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.

Were they winterized? With what?


Jabsco impellers are neoprene and are stiffened by polypropylene glycol AF (EG is OK). One winterization is enough to ruin them.

[S/V Illusion]

Among the least expensive things to change annually.

[Jim Cate]

Originally Posted by capt jgw

Bingo. If they're cracked, you waited too long.

Why is that?

When blades have come off... that's when you have waited too long, and IME it is a long time between when cracks first appear and the blades start to shed. Like the OP, I replace mine at around a thousand hours.

Jim

[hpeer]

I have had WIDE variability in how long the impellers last. Some seem to go forever, others loose blades shortly. Dunno.

[Orion Jim]

I change mine every three years, cheap insurance. Never found a cracked or missing blade which means my timing is perfect.

[skipperpete]

There are a lot of variables that affect impeller life, the size of the cam can significantly reduce the life as can high restriction either to output flow or suction flow. Generators are often hard on impellers, particularly the 2 pole units that hit 3000- 3500 rpm as soon as you press the starter, they don’t give you much time to check the overboard flow before shedding the blades. I find it easier to either point the infrared temp gun at the cover plate or just rest the back of my fingers on the cover, if it gets warm and then warmer.... there’s a flow problem that needs fixing.

[kmacdonald]

Originally Posted by thinwater

Were they winterized? With what?


Jabsco impellers are neoprene and are stiffened by polypropylene glycol AF (EG is OK). One winterization is enough to ruin them.

They were never winterized. They were less than 2 years old.

[carstenb]

A new impeller for our Yanmar costs about $25. We change annually even though there is no evidence of wear. This is simply preventive maintenance. The cost of a catastrophic failure (say while trying to negotiate a narrow channel into a harbor in heavy winds) is a nightmare.

The cost of owning and maintaining a sailboat is high - this is one of the low expenditure items

[Mickeyrouse]

An impeller on a laid-up boat is aging even though the engine is not running. Because the impeller is not turning, some of the impeller vanes tend to “ take a set”, meaning those resting on the cam conform to the bent shape they assume in that position. Microscopic cracks will tend to form where the base of the vanes meet the impeller hub. This is where just about all impellers fail. In quite a few years of sailing I have never noticed wear on the impeller tips, though if the pump is pumping silty raw water no doubt it could happen. I recommend carrying not just spare impellers, but a complete pump assembly as well. I have had impellers last for years, others just a season or two.
On our boat’s engine, it’s just about impossible to change the impeller without first removing the pump anyway, so I just would rather not worry about dropping any small parts into the bilge while in some isolated place. Spare pumps are usually reasonably priced on ebay, and unless the body and shaft are totally shot, rebuild kits are available too. And don't forget the fittings.

[capt jgw]

Right. I take mine out in the fall. I don't always replace them, if they look perfect I might keep them. But I don't put them back in till spring. They don't take a set that way. If I do replace, it's not till spring and I keep the old ones as spares. I do leave a note at the ignition switch reminding me about "impellers out, drain plugs out" etc.

[rslifkin]

Even with winterizing, etc. I change mine every other year. At change time, the engine impellers are typically getting a bit stiff (I change before launch in the spring, so this is after a second winter sitting in antifreeze). Typically no noticeable wear, no cracked blades, etc. With the stiffening over the winters, the typical failure mode if run too long would be a failure to prime if it gets an air bubble during winterizing or on spring startup. As they stiffen, they lose their ability to self prime before their ability to pump water adequately is compromised.

On a long trip without winter storage, I'd probably change them somewhere around 300 - 500 hours. I don't think I'd be comfortable going past 500 hours, too much risk of needing to do an unplanned change (which is a pain on my engines and would be very challenging without waiting for the engines to cool first).