How often should you replace the raw water impeller?

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CalicoJack

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I changed my Jabsco impeller on Saturday. Two years old and it looked as good and soft as the new one which replaced it, in fact it was really difficult to tell the two apart. My question is is two years too soon, or was this a good piece of preventative work?

Nigel
 
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IIRC on my Yanmar 1GM10 it is either 300 or 500 hrs.
Mine never get near that.
I replace always at the start of the season.

For what they cost I think you need to know it is in good condition when miles from anywhere blatting along.
Peace of mind
 
I'd check each season for wear, cracks, loss of flexibility (bit subjective, that one!) and any failure of the bonding of the rubber to the armature. Replace as a matter of course every 5 years or so.
 
I checked mine at the beginning of the season and it looked fine. It failed on our 2nd outing and I had to push the boat back with the tender with a 2.5hp outboard. It will be replaced every season now and I'll make sure I have a spare on-board.
 
I replaced one on a tugs generator which had lasted 12 years. It had failed but only lost two lobes. I only found out how long it had served when entering the overhaul in the records. Incidentally it had a small smear of copper grease on the splines of the shaft which was still visible and the impeller pulled out with thumb and fore finger as if fitted the week before. Needles to say I cleaned shaft and reapplied more coppaslip.
 
Worth remembersing that the body pump itself will wear - especially if you are in silty water
I would change the pump at 2000 hours
 
Inspect annually, look for set in the vanes, tiny cracks in the vane roots, flexibility and replace on condition. Replace at 500 hours or so ( 6 to 8 years for me ) I replaced my pump 4 years ago and the impeller fitted with the pump is still in place some 280 hours later.

Fit a flow sensor and EGT sensor and alarms.
 
Glad I checked mine today
impellersmall_zps04e6b182.jpg


This one was new in April (I've done quite a few hours since then though) and five blades were perfect, the sixth almost off. First one I've had go that way, normally there seems to be small cracks or signs of wear and then I change it for new keeping the old as an emergency spare.
 
aslabend said:
Glad I checked mine today
impellersmall_zps04e6b182.jpg


This one was new in April (I've done quite a few hours since then though) and five blades were perfect, the sixth almost off. First one I've had go that way, normally there seems to be small cracks or signs of wear and then I change it for new keeping the old as an emergency spare.
Click to expand...

Looks to me as though four blades are perfect, one warped, one almost off.

I'm with others who change at the start of each season with a new as spare.

Cheers
 
jon711 said:
Both with conditions, if the engine is not used the vanes take a "set", but if it is used a lot then it wears out. I personally would replace at the start of the season, but, if the old one looks good, keep it as a spare...

Jon
Click to expand...

+1

Royce Creasey explained the art of practical motorcycle maintenance as replacing things before they go wrong, but only just before. However for boat engines, I'd say the aim is replacing them before they go wrong, full stop.

If you lose an impellor vane, you've got maybe 5 left, but the one you've lost will likely be blocking the heat exchanger. This might not happen at a critical moment, but on the other hand....

PS If anyone can suggest another use for several slightly worn impellors, please let me know! ;-)
 
I have heard in the past, that a neoprene impeller if soaked in hot water for a few months will lose the vane set, but have no proof that it works. I would guess that that would not work with nitrile. The difference in the Jabsco part numbers, Neoprene is xxxx-0001b and nitrile is xxxx-0003b.

Good luck

Jon
 
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