Why remove impeller?

[pugwash]

In one of the posts about winterizing there was a query about whether or not to remove the raw-water pump impeller. I've just come across winterizing advice from a US outfit called Boatdiesel which says: "Filling the raw-water circuit with anti-freeze will swell the pump impeller and render it useless. Remove the impeller if you use anti-freeze."

Is this right? I don't remember seeing it discussed.

 

[Aja]

Usually remove mine as a matter of course. There is always the chance that if the impeller is sitting in one position for any amount of time that the blades will become damaged.

Regards

Donald

 

[gunnarsilins]

I always fill...

...the raw water circuit with a anti-freeze/water mixture and leave the impeller in place.
In spring time I always remove the impeller for a check. If I cant find any cracks or signs of wear I leave it for another season.
I´ve done this for years and never seen any influence from the anti-freeze.
I´ve heard the same regarding marine toilets, that the various rubber parts would be affected by anti-freeze. The same story, I have flushed them with an anti-freeze mixture for years without problems.

 

[ccscott49]

Re: I always fill...

I can't understand this either, why would antifreeze attack impellors, when it doesn't attack the rubber/silicon hoses in the cooling system and also does not attack nitile rubber "O" rings. of which impellors are made and is designed to be used with rubber components. Absolute rubbish! IMHO

 

[brianrunyard]

I always remove mine, as I believe it prolongs the life, as there's a chance of the blades becoming distorted sat in one place for 6 months.
There's no extra work involved, as it needs to be checked before the new season anyway.

Brian
http://homepage.ntlworld.com/brunyard

 

[steffen]

How on earth do you replace the impellor AFTER filling the system with anti-freeze without draining the anti-freeze out again. On my Yanmar 3GM the pump in rather low on the system and when opened it it disgourges half the contents of the engine into the bilge.

 

[brianhumber]

Re: I always fill...

I agree, article must have been written by a well endowed male American bovine animal making poo poos.

Brian

 

[tome]

Leave it in for the winter and replace it in the spring.

For the sake of 20 quid, why not replace it every season? I had one go mid way across Lyme Bay couple of months ago in a seaway and it took me an hour to replace it and get under way again. Reckon it added 2 hours to Dartmouth, and I'd have arrived in time for a pint otherwise. Karen wasn't feeling great and it's quite stressful when steam appears from below and through your cockpit lockers.

I've since fitted a speedseal and carry 2 of all engine spares including filters. If I use one, I replace it at the next port of call. If my impellor goes I can replace it knowing I've still got a spare onboard.

I plan my sailing to be as stress free as possible. If I had to make an impellor out of a used banana skin I reckon I could give it a fair shot, but I prefer not to.

 

[faustina]

Despite the dismissive comments above this warning is certainly not 'BS' and some impellors are indeed affected by anti-freeze. Those that are worst affected seem to be those that offer high dry-running tolerance (the Globe impellors that are/were sold by ASAP for example). I have first-hand experience and can vouch for the advice from your American source

 

[alanporter]

Some of the antifreeze sold in North America contains alcohol ( Indeed, some are just alcohol). All rubbers, and some synthetics used in seals, O rings, etc, are damaged by alcohol. I doubt if the American reference you saw was referring to glycol antifreeze. When I first moved from the UK to Canada it took me a while to adapt to the different practices here.

Alan Porter

 

[MedMan]

At the end of every season, once on the hard, I do the following:

1. Stuff a hose pipe into the cooling water intake and leave the wife holding it in place so it can't jump out.

2. Run the engine for 4-5 minutes to flush out the salt water and replace with fresh.

3. Having removed the hosepipe and sent the wife to make a cup of coffee I close the intake seacock, remove the top to the strainer housing and stick a large funnel into it.

4. Run the engine for a final 1-2 minutes whilst slowing pouring an antifreeze mix into the funnel.

5. Remove the impeller, mark it as used and keep as an emergency spare. True, when I remove the impeller some antifreeze mixture runs out to be replaced by air but so what? Air has rather less tendancy to freeze than water!

6. Fit a new impeller the following spring.

So why remove the impeller if I am going to fit a new one anyway? Don't know really - I just always have!

David Teall

 

[Gunfleet]

Your wife seems very patient. Most of the recent models will tell you to hold own funnel and fetch own coffee.

 

[Plum]

In 20 years of boating I have never removed an impeller over winter and have never had a problem. It should, of course, be iremoved for inspection periodically, which I usually do in the spring.

 

[Chris_Robb]

Re: I always fill...

I do as you do - I have been told quite the opposite about glycol - it is actuially a rubber preservative! My Perkins Engine manual says so too! The lavac Loos also benefit in the same way.

 

[BrendanS]

Re: correct and incorrect

OK, a little complicated this one, but bear with me, it all makes sense in the end:

There are different types of glycol antifreezes. The old standard one is ethylene glycol. Cheap, but very toxic. Many US marinas will not allow use of ethylene glycol, and so many US boaters use propylene glycol. Propylene glycol is just as effective, is a little more expensive, but more importantly is non toxic, and can even be used in food products. propylene glycol is now used as a matter of course in many antifreeze applications because of the difference in toxicity.

In addition, pump impellers are made of different materials. The common ones are made of nitrile rubber. There are others e.g flexible impellers made of neoprene rubber. Neoprene rubber swells in propylene glycol.

The advice you read was from a US site, who are probably used to these different combinations of rubbers and antifreeze. Suspect they don't wan't to get into all this detail so just say that impellors can be affected by antifreeze.

An excellent site which shows how different rubber materials are affected by different chemicals is http://www.efunda.com/DesignStandards/oring/oring_chemical.cfm?SM=none&SC=Ethylene Glycol#mat It says o-ring, but actually applies to anything made of these rubbers. You can select a rubber or chemical, and then see what compatibilities there are