Types of Impellers

[DAKA]

For years the forum has debated how long impellers should last with some posters saying change each year and some saying check each year and change every 2-3 seasons.

The reason for the variance is the material the impellers are made of.

Nitrile or Neoprene

Neopreme is the one you want, it is hydraulically better .
It is softer , easier to fit/remove and is cheaper !

Nitrile is harder and more difficult to fit/remove.
It has a memory in that as it is in a hot engine it is pliable, when the engine cools it becomes hard again. As each vane is now moulded to the pump housing the next time you attempt to start your cold engine the vanes will be ripped out the pump housing causing cracks and eventually vanes break off and circulate round your cooling system risking blockages.

Nitrile impellers are suitable for bilge water where heavy contamination of fuel and oil is expected.
Nitrile melts at a slightly hotter temp BUT is more likely to fail if run dry than neoprene as the neoprene has less friction (softer) and doesnt over heat when dry as fast as nitrile.
Neither should be run dry .

Why the post.......

Several years ago I suffered with Volvo Penta parts supplying Nitrile .

I started to buy direct from Jabsco.

About 4 years ago I found Nitrile fitted to my Cummins-Mercruiser as standard new fit.

I was about to post this a year ago but Jabsco assured me that all new cooling pumps were supplied with neoprene impellers.

However it has recently come to light that some Nitrile impellers are still being sold as suitable replacements for engine cooling.

spot the difference


example 1 thought to be nitrile ) 29 hours

Example 2 Neoprene ) 2 seasons and still a good carry on board spare ready to go back in !

When buying an impeller check it is neoprene (warmer to touch and more pliable) note the embossed pattern on the side cross section.

Avoid the colder to touch, flat cut cross section, harder to bend ones like this.

 

[kashurst]

interesting post - I by mistake ordered a pair of impellers from keypart.when they came they were quite soft material and I then realised that they were not volvo parts but a cheaper copy part. I sent them back and got a set of genuine volvo impellers. However bearing in mind your post would the copy parts have been better??

 

[DAKA]

Without seeing them obviously difficult to comment but almost certainly yes !

And you need to inspect the ones you have fitted before they crack up.

 

[Firefly625]

Thanks Daka, yes and interesting post... I had no idea there was a difference in material used... I thought they were black rubber...

(Nitrile or Neoprene who would have thought?)

When Volvopaul changed my impeller last year it was in great shape, but as my spare had become a bit hard over the years of not being used I bought a new Jabsco impeller (the black rubber type , but hopefully Neoprene) which VP fitted and we kept the one removed as our new spare. With just the one engine I think I am happy to pay out for a new impeller each season unless VP advises me against...

 

[Latestarter1]

DAKA............Spot on post!

 

[Philiz]

Thanks Daka, I'd always just assumed they were all made out of the same material. I've fitted genuine Volvo in the past but I'll get Jabsco now. Very useful info.

 

[DAKA]

I'm not intending having a go at any manufacturer .

I havent posted in an attempt to get everyone to fit non standard parts.



You should be able to buy your replacement impellers from your manufacturer but just make sure its neoprene and not a Nitrile one.

Having said that, anyone outside their warranty period may as well buy direct and be sure the correct impeller is used, its a bit of a mystery how nitrile ones are ever getting into circulation as boat engine cooling parts, the only advantage they have is that the jabsco part number is easily removed in order to add your own identifying mark, alright a little pop .

 

[Mike k]

I'm not intending having a go at any manufacturer .

I havent posted in an attempt to get everyone to fit non standard parts.



You should be able to buy your replacement impellers from your manufacturer but just make sure its neoprene and not a Nitrile one.

Having said that, anyone outside their warranty period may as well buy direct and be sure the correct impeller is used, its a bit of a mystery how nitrile ones are ever getting into circulation as boat engine cooling parts, the only advantage they have is that the jabsco part number is easily removed in order to add your own identifying mark, alright a little pop .

As promised Peter this is the genuine mercruiser impeller i recieved , I have been onto them but cant seem to get an answer if its nitrile or neopreen- the code says 17018 0 and the last digit is not legible it could be a 1 or a letter T,P or R who knows.It states its a jabsco and the code numbers below the serial number is 10 14 ( presume a use by date). I have been on to ASAP to try to get them to specify my pump i said i thought the number Spi d suggested and they are tryning to see if they do match.Its such a pain ( for customer- but good for thier business) that engine manufactiurers fit the jabsco pump but then recreate their own reference numbers and its difficult to relate back I am looking forward to hearing back from ASAP- ASAP.Thanks again
Mike

 

[DAKA]

I am 99.9% sure Spi d has correctly identified your pump.

I am 70% sure your impeller is nitrile but from a photo its impossible to be sure.

put it in the fridge for 10 minutes and then see if the vanes easily bend when cold, or if you need to press hard with your thumb.

If they will refund you then take the refund.
Anyone else could risk it but with your set up you really should ensure it is neoprene and if ASAP can supply a jabsco neoprene one and others dont know what they are selling you then get the neoprene one. IMHO

Qualified

I am a bit of a perfectionist and most would just pop the impeller in and not worry about it and not have any problems.
I'm just a pleasure boater, your muckanic should be able to help you.


Keep you eye on ebay for a new pump, there are a lot of boats like yours where you cant get to the impeller and people carry extra pumps, when they sell their boats the spare pumps go for peanuts

now having stated I am a perfectionist, I note your pulley is a bit rusty and this will eat away your fan belts in no time.
If you are just doing a few local hops then not an issue but if you intend to cruise you need to wire brush the rust off and change your belts while the 2x hose are off which will save time.

Try two 1060mm x 10 mm or two 1063mm x 10mm .

You have no teeth which is fine, some prefer teeth which will work equally well and may help to keep the rust at bay.
The pulleys are large enough not to warrant teeth , either will do.

 

[mm1]

29hrs?

Daka just out of interest why was the impeller in pic 1checked/ changed @ only! 29 hrs, regards mm1.

 

[DAKA]

engines had just under 30 hours on when I bought the boat.
I changed the impellers as you do.

 

[mm1]

?

So how long had it been in situ &in what conditions ?.you see where I am going with this ! .the cracks look very uniform,regards mm1

 

[DAKA]

not really.

if you study the vanes you will note curve scratches and gouges .

as hot flexible nitrile nestles into the cam holes and ports and then cools they become lodged in each nook and cranny.

when you start the engine cold the nitrile is wrenched out, you can see the scratches, that is why the cracks and scratches are so uniform .

you can also clearly see wear where the vane joins the hub, this is from the inlet of the pump housing.

Ive added another photo above.

 

[mm1]

?

Whilst I bow to your knowledge on this subject I still think there is a little more going on here!.I have changed many/many impellers & have never seen one with such extreme damage.are you sure it was not run dry/very hot&or in a very silty/sandy environment ,regards mm1

 

[DAKA]

clean water.
I cant be 100% certain but the previous owner wasnt an idiot.

I can say that the impeller I took out as pictured above looks similar to the other side and similar to other nitrile impellers I have removed from my Volvo penta engines which were also nitrile and I know they were never run dry .

Perhaps all the impellers you have removed have been neoprene, technically they should have been

 

[mm1]

Ok let's hope I have got the right ones as they go in on Sat,cheers mm1.

 

[DAKA]

Hope it goes well

And Im very keen to see photos of new ones, and who supplied them and old ones to see if we can tell if they are neoprene , which from what you have said they probably are

if you dont want to post on the forum your make of engine and who supplied the parts last year perhaps I can pm you my email ?

when I say who supplied them, Im not really interested in which dealer, just if they are manufacturers network or jabsco

 

[mm1]

impellers

Hi Daka so engines are VP AD 41P DP(lovely motors ,simple/easy to work on)& i can return 2mpg (10mtr targa)but i digress,i have VP OE ones,i agree they are harder to work with.purchased from a very good source in cobbs.i have tried non OE ONES but they looked alot flimsier but they did the job!& @ half the price,the old ones are out allready & show no problems at all 120hrs,every time i look @ them i wonder why i change them every season,peace of mind i suppose.not sure i am @ the loading picture stage yet i have only been on here for 10yrs man give me a break!!,anyway all good info & thanks for taking the effort,regards mm1.

 

[DAKA]

My last boat had the adaq41 too , great engines

Okay full story , this started almost 10 years ago !
My mate had 42s and together we would cruise round Uk/france/holland when diesel was 25p l and heating oil 17p , filling up was more of a nuisance than an expense !
We had to change impellers every season and occasionally inbetween too.

We both had issues with VP harder impellers until we found some impellers in france for under £10.

They were softer but we both found they were as good as new after two seasons.

Several years later, a bit of research and I post as above, the French impellers were almost certainly neoprene.

Cant be sure what you are about to refit but my experience is that neoprene are more reliable as engine cooling impellers.

It would be interesting to find out what Volvo are supplying as they dont sound like Jabsco neoprene, Mikes mercruiser one had jabsco on it, can you see jabsco on your Volvo Penta ones ?

 

[mm1]

ok if we are reminiscing fuel in cowes @ 18p pl & looking around Richard Branson virgin atlantic challenger in cowes(what a great boat).from memory i think it just says VP on them,will check on sat,mm1.