Chasing impeller vanes

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Mar 20, 2007
500
Catalina 355 Kilmarnock, VA
My boat was hauled on short notice at the end of October for Sandy, so I had to do my winterization on the hard. Somehow in the process of running antifreeze through the raw water side of the Yanmar 3YM20, the flow got interrupted for a few seconds, and then the pump quit working:cry:. When I checked the impeller, it was missing 2 vanes. I replaced it with an old one and finished the winterization without any problems. As I thought about it this winter, I figured I'd better find the broken-off vanes before I recommision this spring, so went searching for them yesterday. Started with the pump outlet - no sign of them. Removed the molded pump-to-heat exchanger hose and reamed it out - nothing. Ended up having to first remove the alternator to get at the HX inlet, finally got it unbolted with much loss of skin on my hands, and there they were, stuck in the HX inlet pipe and nearly completely blocking it. Rodded out the HX passages while it was open and reassembled with new O-rings. Altogether, about 2-1/2 hours of work for a few seconds of dry running. Moral: don't let your raw water pump run dry:doh:, and carry a new impeller and set of o-rings or gaskets in case you do!
 

Ted

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Jan 26, 2005
1,222
C&C 110 Bay Shore, Long Island, NY
Just wondering, when was the last time (or number of hours ago) you put a new impeller in your water pump? It sounds like this may have happened even if you didn't run it dry for a few seconds. Glad you found those bits before they caused other problems.
 
Mar 20, 2007
500
Catalina 355 Kilmarnock, VA
Just wondering, when was the last time (or number of hours ago) you put a new impeller in your water pump? It sounds like this may have happened even if you didn't run it dry for a few seconds. Glad you found those bits before they caused other problems.
Changed it last Spring - it had about 50 hours on it. Made by Johnson Pump, impeller was a Yanmar OEM replacement.
 

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Jun 21, 2007
2,093
Hunter Cherubini 36_80-82 Sausalito / San Francisco Bay
Just a few seconds of dry shouldn't have caused a such failure unless the impeller was already in trouble or maybe the temp was so cold, the vanes were frozen to the pump casing?

Wish that I could remember (from SBO posts and also my experience) the brand of impeller that reportedly failed very readily. Maybe you had one of those? A few years back, mine didn't fail, but on inspection, after less than one year use (<50hrs), I observed each vane had cracks at it's base joint with the center section. Sadly, my problem impeller I think may actually have been supplied by my local Yanmar distributor. The replacement impeller still looks like new two years later. No cracks and the rubber is still very pliable. And once or twice I even have run it dry for a minute or two. Notwithstanding its continued good looking condition, I have two spares on board. One of them will be installed this spring!
 
Nov 23, 2011
2,023
MacGregor 26D London Ontario Canada
I got at my impeller on Satutday. What a surprise when I firts opened the bottom end of my OB. That is oil and soot. Ick! Glad I decided to check it. At least I know the PO used lots of oil in the mix!
The impeller looks ok with no cracks but at $10 I would rather be safe and get a new one. I'll keep this as a spare.
The other picture is the inside of my exhaust housing. Needs a good cleaning just like the boat did.
 

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Feb 6, 1998
11,453
Canadian Sailcraft 36T Casco Bay, ME
Changed it last Spring - it had about 50 hours on it. Made by Johnson Pump, impeller was a Yanmar OEM replacement.
I doubt that failure was caused by heat. When there is a heat failure the little round portion at the end of each vane is usually worn flat. I suspect age and a "winter set" likely caused the failure of those two vanes.

Did you remove it for winter storage and or did it sit in PG antifreeze during the winter...?

I have found, after removing and replacing far too many impellers to keep count of, that yearly replacements are the usually best option. I can nearly always find cracks in the root or vane of even a 1 year old impeller, any cracking is unacceptable..

For the $16.00 - $20.00 it is worth it to me to simply replace it each spring...
 
Mar 20, 2007
500
Catalina 355 Kilmarnock, VA
Did you remove it for winter storage and or did it sit in PG antifreeze during the winter...?
Checking my maintenance records, I actually replaced it a year ago last spring, so it had been through 2 seasons. I used to replace it yearly, but the old ones looked so good I went to 2 years. I'll change that now. At least it happened during winterization and not when I needed the engine...
 
Sep 25, 2008
1,096
CS 30 Toronto
After winterization, I remove it and place on top of the motor. In the spring, I put them back in before draining the antifreeze. They seems to set and crack in the cold winter months.

I replace it every other year even if it looks good. I have a Volvo and parts are pricey.

Besides, I have to remove the AF anyway. It's illegal to dump it in the lake where I sail.
 

DougM

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Jul 24, 2005
2,192
Beneteau 323 Manistee, MI
There was a thread awhile ago about Globe impellers having an unusually high failure rate...
I don't recall seeing anything about Johnson impellers being a problem.

Out of curiosity, Is salt water the culprit in causing early/frequent disintegration of impellers?

. I sail in fresh water, and have changed impellers just to be on the safe side, but have seen no evidence of impending failure. The vane roots look good and the impeller retains its flexibility. The good news is that they don't cost very much and are easy to replace.
 
Feb 12, 2013
97
C&C 35 MKIII k/c Rock Creek, Chesapeake
Like Maine Sail, replacing the impeller is part of my spring commisioning.

Dave
 
Feb 21, 2008
363
Hunter 33 Metedeconk River
Took a few courses at Mack Boring a few years ago on maintenance but have lost my notes in the superstorm Sandy. However, every year after winterizing I would pull the impeller and keep it in glycerin. I would check the vanes for cracks or wear and toss as needed. In the spring I would install a new impeller and keep the one sealed in glycerin as a spare. Don't think I would come up with this scenario on my own so I am guessing it was from them. Also, just in passing, I always had a new extra impeller on board AND a package of those pesky little screws that hold the pump cover on in case of stripping or loss.
 
Oct 9, 2008
121
Marine Trader Sedan Mystic, CT
I too took the Mack Boring course and at the time (10 years ago) they suggested removing the impeller and storing it in cheap olive oil for the winter. I then install a new one in the spring and keep the old for a backup. I now have 3 in olive oil for backup. I will need a new jar soon.
 
Jul 13, 2010
1,077
Precision 23 Perry Hall,Baltimore County
Reading this with interest.Ive had my boat and 4hp yamaha since 2010. It is my first outboard motor. As such, when it runs, I get a dribble of water out, don`t know if that is the corect flow or not. I decided over this winter to replace it and have been researching the process. Anyone with any tips or "watch out for`s" wpould be helpful. Thanks., David
 

kenn

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Apr 18, 2009
1,271
CL Sandpiper 565 Toronto
David, the 'piddle' from an outboard should be fairly strong. If it's just a dribble, and your outboard is overheating, you might have an impellor problem. If the engine cooling seems fine, it might just be a restriction in the piddle hole.

Impeller changing - Here ya go, David. This guy seems to mention all the little things that the service manual leaves out. Obviously you should also have the service manual.

Last summer I helped my friend solve an overheating problem with a 3L Volvo inboard/outboard. It was due to broken paddles and yes they were stuck just at the heat exchanger input.

It seems to me that every motor with an impeller-type water pump should have some sort of built-in trap downstream that's intended to capture impeller paddles, since it's a given that sometime during it's life, every engine will blow an impeller.
 
Mar 26, 2011
2,964
Corsair F-24 MK I Deale, MD
Checking my maintenance records, I actually replaced it a year ago last spring, so it had been through 2 seasons. I used to replace it yearly, but the old ones looked so good I went to 2 years. I'll change that now. At least it happened during winterization and not when I needed the engine...
Perhaps it happened because of winterization. What type of antifreeze (ethylene glycol or propylene glycol)?

Yanmar (most engine brands) uses a neoprene impeller, which is incompatible with propylene glycol (about 2x-3x increase in stiffness). It is compatible with ethylene glycol. It would be nice if they would tell us this stuff.

http://sail-delmarva.blogspot.com/2012/12/eg-vs-pg-conventional-wisdom-that-is.html

I've been testing a variety of chemicals on joker valves (thank goodness Jabsco and Groco were forthcoming with donations), so I am not guessing. Any other chemicals I should add to the list?

http://sail-delmarva.blogspot.com/2013/01/what-should-i-be-testing.html
 
Feb 12, 2013
97
C&C 35 MKIII k/c Rock Creek, Chesapeake
Perhaps it happened because of winterization. What type of antifreeze (ethylene glycol or propylene glycol)?

Yanmar (most engine brands) uses a neoprene impeller, which is incompatible with propylene glycol (about 2x-3x increase in stiffness). It is compatible with ethylene glycol. It would be nice if they would tell us this stuff.

http://sail-delmarva.blogspot.com/2012/12/eg-vs-pg-conventional-wisdom-that-is.html

I've been testing a variety of chemicals on joker valves (thank goodness Jabsco and Groco were forthcoming with donations), so I am not guessing. Any other chemicals I should add to the list?

http://sail-delmarva.blogspot.com/2013/01/what-should-i-be-testing.html

Which is why I change my impeller after after I comission in the spring. You confirmed my thoughts that the antifreeze might/ does affect the impeller.

What have you found about the joker valves, although that doesnt sit in the antifreeze solution like an impeller would. Are you looking at the fresh water systems we use and also the pumps. Some people use impeller type pumps for their fresh water and some use diaphram pumps. Most of us flush with PG to winterize.

Dave
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
Which is why I don't fill the raw water with anty but just drain it. Certainly easier to pull some hoses, take the back off the pump and walk away than playing with buckets and valves IMHO.
A little known fact about freezing pipes is that as long as there is some place for the ice to expand into (it does not all freeze at the same time) it will not "crack your pipes". so if you can get some aire space into each pipe or leave it open at one end it can freeze solid and not crack anything!!!! That is why they tell you to let your faucet drip during freezing weather in the south. It is not the warm water coming in from the ground that "keeps it from freezing" it is that the ice has somewhere to expand into at low pressure. I've seen fully frozen pipes that have not cracked using this method.
 
Jun 6, 2006
6,991
currently boatless wishing Harrington Harbor North, MD
Oh yea, I'm on my 5th season using the PO's impeller and it looks fine. I've not had one loose a vane yet in 10 years of sailing.
 
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