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View Poll Results: How often do you replace the impeller on your raw water pump?
Once a year, or more frequently, depending on engine hours 18 10.98%
Once every two years 57 34.76%
Once every three years, or more 47 28.66%
Only after it fails 20 12.20%
I've never replaced it 22 13.41%
Voters: 164. You may not vote on this poll

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  #1   IP: 75.210.87.216
Old 08-12-2007, 12:18 PM
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How often do you replace your impeller?

I'm a little surprised this hasn't been mentioned...
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  #2   IP: 4.243.25.157
Old 08-15-2007, 04:38 AM
starnesent starnesent is offline
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ive never done it -

yes im Les & im an

impeller virgin - :O

my sisters sailboat has an A-4 a 70's model.
the A-4 is in a 29' Islander very nice boat.
great shape,but unused as a sail boat. it was bought to live on.
& there it sits ~ well docks. . .

I'm going to either put in a new pump & rebuild the original -
Or convert it to FWC & then maintain that impeller
& yes i will be sure to replace the impeller ever 3 or so years no matter what the hours it actually runs. as the impellers look to be made of material that might deteriorate with age. The FWC pump would be right up front easy to maintain compared with the location of the RAW water pump up & under & behind the starter & Alternator & over & under a hump of fine looking {but} hard teak.

oh why fix a boat tat don't actually sail you ask (?)
we are trying o get her to sell it as she never
sails it.

yup

* shucks i have to fix the RAW water pump anyway.
ppl in the know [Don] informed me the FWC still makes use of the RAW water to cool the FWC tank
[that makes good sense] so i need to get the new pump from moyer & while im at it a new impeller for the old pump
to get it in running shape in case its needed on the dock (?)
yup another 350 mile drive - shucks id rather pay someone to do it right.

Last edited by starnesent; 08-23-2007 at 01:19 PM. Reason: update
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  #3   IP: 69.29.217.249
Old 08-23-2007, 12:54 AM
brad@elevated.org brad@elevated.org is offline
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I've learned my lesson

I learned my lesson on our last cruise. My impeller was in for just at two years--maybe 50hr of engine time. When I stopped at our first destination I found 2 out of 8 fins remaining I retrieved 4. Two days later I blew a head gasket. Coincident?

They are relatively cheap and easy to change, at least on my a4. I may change it every time I go out!
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  #4   IP: 38.118.52.41
Old 08-23-2007, 07:34 AM
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Brad,

The only way I see your head gasket failure relating to your impeller failure is if the engine severely overheated and you still had one of the older (paper) head gaskets installed. With the advent of the Victor steel-reinforced graphite head gaskets in the early nineties, head gasket failures have reduced to almost zero for any cause, including overheating.

Don
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  #5   IP: 24.47.216.175
Old 09-01-2007, 10:24 PM
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Up here in the northeast I like to check our cooling water impellor every spring and make sure to drain all the liquid out of it in the fall. I also carry a spare and check to make sure there is water flowing out the exhaust every time the engine is started.
I learned to be diligent about this crucial piece of equipment after launching in our second season. At that time I did not even know that the water pump had a thing called an impellor and left liquid in there that probably froze. I went out on a windy day and the engine overheated while we were bobbing about in 3' swells in a mooring field in LI Sound. I have vowed to never allow myself to be in that position again.
Also, be very careful when running your A4 while on the hard and always
ensure that there is cooling water available and that it is being pumped out the exhaust pipe. Never put your engine in gear while on the hard; the cutlass bearing expects water to be there to lubricate the shaft as it turns.
Live and learn.
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  #6   IP: 142.68.126.98
Old 12-31-2008, 07:07 PM
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On the big twin power boat we had for a decade, I changed them annually, owing to a bad experience first year or two and a fair bit of summer cruising. For this smaller engine, I like Don's advice from the MMI pump instruction kit, and I dreamed up some additional reasons to change the impeller. Here is my personal checklist:

1. Fins appear stiff, cracked, have a pronounced "memory" (bent lobes), or any other sign of damage.
2. Every two years of average summers in clear water.
3. Every 200 hours (= 800-1000 miles under power), more often in sandy water.
4. Episode of running pump dry more than a few seconds (during startup, or episode of clogged strainer).
5. Episode of engine overheating, regardless of cause.

Remove impeller every fall and put it back in every spring, so the vanes do not remain bent up all winter (leave a reminder somewhere obvious for spring). The new MMI pump makes removal a snap.
Carry at least one spare.
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  #7   IP: 71.233.251.176
Old 12-31-2008, 08:42 PM
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Cool How often do I replace my impeller?

Interesting distribution of responses given that I'd expect most people on this site are fairly interested in maintaining their engines reasonably well. But, some of us are prudent, some of us talk about being prudent and some of us are fairly cavalier.

Anyway, I'm going into my third year with my Catalina 30 and have yet to change the impeller. But, I check it several times each season, and carry spares and tooling on board at all times. Obviously, I'm due for a swap, whether it needs it or not.

So, for now, count me in with those who "talk about being prudent" and we'll see whether I promote myself to "prudent" in the sping.

On the hard,
Ken - Obsession
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  #8   IP: 68.104.69.129
Old 12-31-2008, 11:03 PM
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I too learned the hard way. Bought my '78 RANGER just before Thanksgiving and just had to get out on the water forgoing any precautionary checkups.

While setting the hook in a secluded cove, the engine temp rapidly rose and zero water was exiting the exhaust.
I knew instantly it was the impeller.

The bright side of that dark cloud is that it sent me searching out info on this (new to me) little engine and I found this extraordinary A4 site! Since then I've replaced the water pump, thermostat & housing, hoses and exhaust hot section. Thank you Don (and all contributors) for this most wonderful resource!

Anyway, back on topic...
I plan on checking mine at least every 50 hours and religiously (or maybe prudently? knitchie) following rigspelt's 5 rules of thumb for replacing.
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  #9   IP: 98.141.38.22
Old 01-01-2009, 01:33 AM
s/v Dearbhail s/v Dearbhail is offline
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I never shut my boat down "for the season", we use it year round here in Norfolk. I made a maintenance schedule for the boat years ago and swap out the water pump impeller every two years in the spring. If there is a reason to go into the cooling system, for example back in May with my side plate problem, I go through the entire system; replace the hoses, hose clamps as required, the impeller, and the thermostat.

It might be my previous experience in submarines, but a good maintenance program prevents a lot of problems.

BTW, Happy New Years and happy sailing!
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  #10   IP: 142.68.126.98
Old 01-01-2009, 09:23 AM
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Quote:
Originally Posted by rigspelt View Post
2. Every two years of average summers in clear water.
3. Every 200 hours (= 800-1000 miles under power), more often in sandy water.
The "200" hours rule of thumb in my list troubles me most. I don't have any technical failure data to base it on, just a sense of what long range cruisers have said from their own experience. The idea is to have a rule of thumb for changing the impeller more frequently than every two years, for example during a long summer of coastal cruising.

I'd be curious to know the typical seasonal engine hours for average North American sailboaters who just start their engines to get out to race course 1-2 times a week, plus once or twice on weekends for day trips, plus a summer holiday cruise 200 miles round trip. Double that to get two seasons in clear water. But there are so many variables on a long cruise: number of days engine runs per week, condition of the water, water temperature, idling time versus cruising time under load, etc.

Guessing at typical engine use in freeze-up communities (obviously highly variable):
Half hour per race night x 2/wk = 1 hr/wk, total race season at 1.5 nights/wk x 16 wks = 24 hours.
One hour per weekend day trip = 1 hr/wk, total summer season at 1 trip/weekend x 16 weeks = 16 hours.
Summer holiday, 2 weeks, 300 mile round trip in 10-60 mile hops, travellng every 3 days = maybe 30 hours (highly variable)? Probably good idea to pull the impeller and check it prior to departure and on arrival home from a summer cruise.
Total = 70 hours. And my guess is that most sailboaters put on a lot fewer engine hours than that, so this probably is conservatively high. Most marina-based power boaters think of 50 hours as a slow summer typical of most boaters, and 200 hours as a moderate use summer including a holiday cruise.
Two such seasons = 140 hours.

So a conservative sailor might use 100 hours (400-500 miles), others might use 200 hours (800-1000 miles).
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  #11   IP: 74.235.209.229
Old 01-03-2009, 06:09 AM
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I don't know how often I change my impeller -- I used to do it once a year
when I was laying my boat up for the winter but now that I take it from
MA to FL, which is about 300 hours of motoring, that interval is much
longer.

I'll change it if I change the antifreeze in the engine at about 1,200 hours
or if the pump shaft seals corrode and go adrift in the pump (in which case
I replace the whole pump as the main chamber is worn out a bit at that
point).

I've never had an impeller fail on me so haven't set up a replacement
schedule for one. Maybe Don can chime in here.

-jonathan
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  #12   IP: 70.22.218.200
Old 04-27-2009, 10:01 PM
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We bought the boat last September so we haven't had a lot of use of it thus far. PO said he put in a new one last spring. I did other things this spring to maintain and improve the engine; the impeller is the one remaining bit of ordinary maintenance. Last Saturday water out the exhaust at all engine speeds was ample and appropriate. I like the idea of removing it in the fall so as to allow the fins to relax, but once having taken it out, why not replace it with a new one, it being just as much work to put back the old one as to replace it with a new one. That's what I think I'll do in the future. As for now, I'll replace it soon, definitely before our cruise downeast in August.

Mark S
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  #13   IP: 138.162.0.42
Old 05-29-2009, 02:52 PM
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First time change out

My thought process was the same as Starnesent. I bought the boat 3 years ago and the boat had been on the hard for two years prior. Understand it was overhauled by Moyer in early 2000s, so mine is probably 6 or 7 years old! I, too, thought the raw water pump, installed with the FWC system was THE pump. After reading several strings here I started to have doubts, so called Don and learned both pumps need tending to. I purchased and received my new impeller and pump back (could not see me bending over the motor to take out the screws and not losing half of them in the bilge). Plan to install this weekend; wish me luck! Thanks Don for your outstanding advice and ability to deal with landlubbers like me.
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  #14   IP: 63.239.69.1
Old 05-29-2009, 04:09 PM
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I replaced mine last year and immediately had water flow issues. I posted about it on this site and Don mentioned that sometimes new impellers in old pumps don't work as well, but that soaking the impeller in MMO for a day or so often solves the problem, perhaps by the impeller absorbing some of the MMO and swelling slightly.

The old impeller looked good (very flexible, no memory in the lobes, no cracking), so back in it went. After that I probably only ran the engine for maybe five hours, tops, the rest of the season. This spring I looked at it again -- still very flexible, no memory in the lobes, no cracking anywhere. I put it back in, but soaked the new impeller in MMO for a few days, then put it into a ziplock baggie in my toolkit for later use.

I'm planning on buying another shaft and snap ring for the new impeller, because if I need to replace one in a hurry I don't want to be fussing around with the snap ring pliers in bad weather or if I'm in a big hurry. Pull out one shaft w/impeller, put in a new shaft w/impeller. Much faster.
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  #15   IP: 206.125.176.3
Old 07-13-2009, 04:21 PM
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BS, That's a great idea! Pre-assembled, and you just slide in the new & can fix the old one later!
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  #16   IP: 76.106.6.207
Old 04-10-2010, 09:37 PM
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Yeah, but I still haven't bought that extra shaft and fittings.

One of these days, though...

I did finally put in that MMO-soaked impeller. It works fine, though I do notice that at very low rpms the engine temp rises a bit -- but now I also have a valve on the bypass hose, so if I need to I can direct more water through the cooling jacket.

She's running great right now.
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  #17   IP: 74.92.224.177
Old 04-11-2010, 01:15 AM
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Which shaft do you need? I have one that I just (last week) got from MMI for a Oberdorfer 202-M3/M7 pump rebuild. I was going to return it because I found (and purchased) a brand new pump for $100 on ebay (the same cost as the rebuild parts). Since I was going to pay shipping back to him anyway, I could ship it to you instead if you want and you wouldn't have to pay shipping.

Qben Oliver
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  #18   IP: 76.106.6.207
Old 04-11-2010, 08:25 PM
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Thanks, but that's low on my list of things to do right now, so go ahead and send it back to Don for a refund. I've got other stuff I want to take care of first.
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  #19   IP: 74.101.129.193
Old 05-27-2010, 11:50 AM
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just put a new water pump in beginning of last season... planning on changing it next season depending how much use it gets this year.


i think it helps to take the impeller out of the pump over the winter so it doesnt get stuck in a certain shape (but im too lazy to do this anyway).
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  #20   IP: 67.210.34.16
Old 06-14-2010, 06:41 PM
jacques debauche jacques debauche is offline
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Impeller replacement

We replace the impeller every two years simply because the things get tired. However, having a boat in which the water pump can actually be seen, and even worked on from a comfortable chair, and having one of Don's wonderful quick removal pump covers, we check the impeller every spring just to make sure it hasn't received mechanical damage. In our previous boat, getting to the water pump was a spelunking expedition, so we were not so conscientious. We paid for that with impeller failures, about every three years.

Pulling the impeller when the boat comes out of the water to avaoid having it take a set sounds like a good idea. Now if someone can just remind me to put it back in - - - .
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  #21   IP: 173.166.26.245
Old 06-14-2010, 09:49 PM
hanleyclifford hanleyclifford is offline
 
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Question spelunking?

Jacques - Francais, Deutsch, Quebecois?
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  #22   IP: 67.210.34.16
Old 06-16-2010, 12:39 PM
jacques debauche jacques debauche is offline
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Spelunking

Spelunking: The hobby or practice of exploring caves (English)
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  #23   IP: 173.166.26.245
Old 06-16-2010, 08:10 PM
hanleyclifford hanleyclifford is offline
 
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Red face English lesson

Jacques - I got it. Spelunking, from the Latin "spelunka" meaning cave. I stand corrected (again).
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  #24   IP: 67.210.34.16
Old 06-17-2010, 11:57 AM
jacques debauche jacques debauche is offline
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MMO treatment of impellers

Since reading about it several days ago, I have been troubled by the implications of soaking water pump impellers in MMO before installation. Presumably the intention is to make them more flexible, and that's what bothers me. In a flexible vane pump such as the Oberdorfer (and the Moyer Improved) the vanes have to be flexible to accommodate the different pump chamber radii in the inlet area (long) and the outlet area (short). However, if the vanes are too flexible, they will bend backward more than intended as they approach the outlet port (as the pressure in the fluid increases) and allow fluid to flow backward toward the inlet port. This has the net effect of decreasing the pump capacity (GPM) for a given rotational speed (rpm).

Presumably the designers of the pump gave some thought to the appropriate flexibility of the vanes to achieve the right balance between effectiveness and durability. By making the vanes more flexible, are we upsetting this balance?
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  #25   IP: 173.166.26.245
Old 06-17-2010, 01:46 PM
hanleyclifford hanleyclifford is offline
 
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Talking oil on impeller

Jacques - I share your concern about the practice of soaking impellers in ANY sort of oil. Some impeller materials can actually be chemically atacked by petroleum products, a possibility we must take into account given the unknown origin of some of the stock.
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