Water Pump Impeller Damage
Hi Folks,
I am new to outboard motor maintenance and am looking for some advice. I have a 2009 115HP Mercury 4st with 150 hours on it. The annual servicing is carried out by a mobile technician and I average about 50 running hours per year. Last year my service technician advised the impeller was worn on the end and may have been damaged by foreign material, such as sand. He replaced the impeller. This year he observed similar damage - see attached photos showing each side of the latest impeller. The damage only occurs on one end. I don't use the motor in sandy conditions, so have discounted this explanation for the damage. My concern is that the impeller is not lasting 100 hours which is the recommended service interval. Any ideas what could be the cause would be much appreciated. I don't want to be committed to having to replace the impeller every 50 hours.
Yewiefish85
Posts: 788
Date Joined: 02/01/11
that's not sand damage, looks
that's not sand damage, looks like there may be a score on the inside of the impeller housing causing it to "chew" out one side
chris raff
Posts: 3257
Date Joined: 09/02/10
Most probably worthwhile
Most probably worthwhile putting a whole new pump kit in , including housing no more than a $100 all up I'm guessing...those fins are shot as well being they are quite bent = less water flow...I'd normally change out impellor annually regardless of hours...problems occur more often on outboards that aren't regularly run unfortunately ...
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strike_zone
Posts: 403
Date Joined: 09/09/10
key way
thats the groove for your key way to sit into its supposed to be there the other mark is prob from where your mechanic let it slip out whilst putting putting it back together all impellor fins look bent after you have run them thats not an issue it actually looks to be in quite good condition but it is a good idea to replace them every 12 months for piece of mind and def dont go by hours for servicing unless you do shit loads of course get it serviced every 12 months again for piece of mind
tim-o
Posts: 4657
Date Joined: 24/05/11
If that was mine, it would
If that was mine, it would have gone back in with a bit of grease no worries. Looks like a bit of melting on one end around the center, prob the end that runs against a stainless end plate. I replaced the whole kit when I bought my boat nearly a year ago and will soon be pullin it apart to give the impeller a coat of grease.
I am, as I've said, merely competent. But in an age of incompetence, that makes me extraordinary.
tim-o
Posts: 4657
Date Joined: 24/05/11
Rethinkin that, not having a
Rethinkin that, not having a nice lip around the center may allow water intrusion to the shaft, looks like rust on it? Grease is good, the shaft would cop some too. Would need to see the housing/end plate, maybe damaged or has rubber deposts on it??? My housing was cooked from being run dry so distortion may cause there to be too much crush on the impeller when installed, the only reason I can see for one end to do that is that there is a stainless end plate and bakelite housing. Im no expert tho, only done one so far....
I am, as I've said, merely competent. But in an age of incompetence, that makes me extraordinary.
Rob H
Posts: 5770
Date Joined: 18/01/12
As the other guys have said,
As the other guys have said, really need to see the housing for possible causes. But id say that was still 100% functional. Id put a new one in if it was apart but the fin angle is no problem at all. As also mentioned above i think, the 2 things that f--k impellors are sand and lack of use.
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The older you get the more you realize that no one has a f++king clue what they're doing.
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NOHA
Posts: 914
Date Joined: 24/06/07
top pic
That impellor is cooked. It has been run dry.
See the little ridge on the bottom pic. It should have them on both sides. Thats how it gets its seal. They are gone on the top pic and the impellor is now useless.
I would look at your muffs as I dont think your giving it enough water when flushing or you are letting it run dry. It only takes a second to overheat an impellor if its dry
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strike_zone
Posts: 403
Date Joined: 09/09/10
not cooked
if you call that cooked then if you seen one that really was cooked it would freak you out the fins melt and break off when you cook it that one is still fine
Rob H
Posts: 5770
Date Joined: 18/01/12
Id agree with SZ on that I
Id agree with SZ on that I think. These work on exactly the same principle as a Jabsco/Johnson. And while the ridge I think you are referring to does have a function, as these pumps are always below water it doesnt really affect these as opposed to a Jabsco that needs to pull up dryish.
Having said that Id replace it if its apart and examine the housing for a cause.
Give a man a mask, and he'll show you his true face...
The older you get the more you realize that no one has a f++king clue what they're doing.
Everyone's just winging it.
NOHA
Posts: 914
Date Joined: 24/06/07
Cooked impellors
Dont worry I have seen plenty of really cooked ones too.
At low revs these pump are positive displacement and depend on the ability to get a seal to force the water up into the motor. If it can get past that seal then the pump will not push enough water and the motor overheat. At high revs the pump has enough velocity to force the water thru the motor.
But regardless. It is happening at a frequent rate and the root cause of his pump damage needs to be found. If the housing was scored the pump would not work but not melt the pump. It has to be dry to overheat..no water. The damage may well be in the housing now as well and both require replacement. But thats still not the cause.
Twin turbo..V8 diesel..Ohh what a feeling!!
No Orange Hats Allowed
Yewiefish85
Posts: 788
Date Joined: 02/01/11
If the housing was scored the
If the housing was scored the pump would not work but not melt the pump
how would a score in the impeller housing cause the pump not to work?, in the first pic it looks like there are small chunks of rubber missing not melted?, i could be wrong tho