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Old 07-17-2012, 11:42 PM   #1
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Water Pump Impellers

My Detroit's use Johnson water pumps. On this last outing I replaced my third impeller on my starboard engine in two years. That makes four impellers for the two engines in two years plus one for my Northern Lights generator. Replacement Jabsco impellers all except the Northern Lights which is a Northern Lights replacement part. Since this is the first impeller for the Northern lights in two years and the first I've installed I don't know the history of the old impeller. However I think I'm burning through the Jabsco impellers at a alarming rate. I'm using Jabsco as replacement as they are easy to come by. Has anybody got a better type or brand of impeller. I understand there are impellers made from a better rubber, has anybody had any experience finding better impellers?
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Old 07-17-2012, 11:57 PM   #2
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We have Johnson pumps on our two FL120s and our first impeller change was five years or so after the pumps were installed. The impellers that came out looked exactly like the new impellers going in. On the advice of our diesel shop we use Johnson-branded impellers. Don't know who actually makes them--- maybe Johnson does--- but we were told they are better quality and last longer than the typical Jabsco impeller.

However, our Onan Jurrasic Edition MDJE 7.5kw generator has a Jabsco raw water pump on it and it's been at least seven or eight years since I've changed it. We use a Jabsco impeller for that application. It's on the to-do list but I never seen to get around to it. We don't use the generator a lot on cruises--- once a day on days we don't run the main engines and only for an hour or so to throw a charge into the batteries and heat water for the day. But so far the water volume and velocity out the generator is exhaust is unchanged so the Jabsco impeller has given us good service. But I do need to change it........
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Old 07-18-2012, 06:07 AM   #3
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I understand there are impellers made from a better rubber, has anybody had any experience finding better impellers?

Impeller life varies with the silt/sand content of the water.

A better filter setup might give a couple of hundred hours longer , but the "fines" are hard to catch.

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Old 07-18-2012, 07:00 AM   #4
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The Jabscos in my Cat 3208s were flawless afer 3 year cycles. 9 months of use, then 3 months out for winterization. Widely used around here without complaint (that I've heard of).

Even had one on my assistance towing boat where sand wore a hole through the pump case before the impeller failed.

What is the type of failure on the Jabsco impellers??? Maybe it's not the impellers.
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Old 07-18-2012, 08:32 AM   #5
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Quote:
Originally Posted by Scary View Post
....... However I think I'm burning through the Jabsco impellers at a alarming rate. I'm using Jabsco as replacement as they are easy to come by. Has anybody got a better type or brand of impeller. I understand there are impellers made from a better rubber, has anybody had any experience finding better impellers?
A friend of mine has a Mercruiser gas engine and he was having problems with impeller life. Together, we noticed that there was a piece broken out of the pump housing and the rough edge was chewing the impellers.

A new pump housing solved the problem. Just something you might want to check.
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Old 07-18-2012, 10:32 AM   #6
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Pump housing feels ok

Maybe these impellers had hardened while in storage. But the vanes were broken off at the hub. All but one of these impellers came with the boat so I'm not certain of their age. I'm going to Oakland today so I will buy spares. I'm going to try to find Johnson impellers if possible. But I think I should be getting at least three of four hundred hours out of impellers. I have about a thousand hours on the Northern lights and this is my first replacement impeller I've installed however I've only put a couple of hundred hours on it since I bought the boat so I don't know the replacement history. On my Cummins 330B's with Johnson pumps I could get about 600 hrs or more.
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Old 07-18-2012, 02:06 PM   #7
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can't go by hours necessarily...broken off vanes to me signals they sat awhile and the inside of the pump was dry started.
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Old 07-18-2012, 11:25 PM   #8
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Impeller blades that break off near the hub are an indication of dry running. At a normal end of life the blades will start to crack about half way up the blade, not near the hub. If it has been run really dry the ends of the impeller will be hard and polished or cracked. Jabsco makes very high quality impellers. My guess is that you either have a restriction in the intake side of the pumps or the wrong impeller is being used.
If you can tell me the Johnson impeller number, I can tell you the Jabsco number that replaces it. At least we can confirm that you are using the correct impeller.
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