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post #21 of 36 Old 07-26-2013 Thread Starter
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Re: Premature impeller failure cause

Roll forward a year. During the winter I had a 1 in. thru hull installed with a new 1 in strainer. Early in the season every thing looked good. Noticed that the engine was running slightly cooler so maybe this was the solution. Unfortunately had another impeller fail right after the 4th of July about a year and a week after the last and about 75 engine hours later. I could tell the impeller was going bad and starting to spin on the bushing by the way the water flow was decreasing and a slight creeping up of the engine temp. Four hour impeller change. Really bad spot for the pump. Regardless of the cause of the problem I think I'm going to try and relocate the pump to make changing the impeller easier. Maybe a crank shaft mount.

My yard is following up with Hansen Marine the Westerbeke dealer as beside my problem they had the same problem on a new boat they were fitting out. Same exact Westerbeke 55 installed. Had the 1 in. thru hulls and 1 in piping right from the start. They are now thinking that the pump might be undersized for the engine or some other design

While the yard is working on Hansen Marine / westerbeke I followed up with Johnson Pump to see if they had any ideas about the causes of the failures. Oddly Johnson Pump had Joe Joyce from Westerbeke email me. He's thinking it is a bad batch of impellers and is sending me a few new ones. I'm there is more to it than that. Anyone have experience with crank mounted pumps? Hard to get a pump that matched the bolt pattern on the crank pulley?
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post #22 of 36 Old 07-26-2013
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Re: Premature impeller failure cause

If the fellow who works for Westerbeke is suggesting a bad batch of impellers, he has probably heard other stories like yours. I'd give it a try with one of the impellers he sent you before you spend a lot of money changing pumps.
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post #23 of 36 Old 07-27-2013
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Re: Premature impeller failure cause

Is it possible there is a machining bur on the incoming or outlet ports on the pump itself.

I think after using up your new impellers that are being sent, the next option would be to bite the bullet and spring for a new pump.

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post #24 of 36 Old 07-27-2013
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Re: Premature impeller failure cause

Am i reading this right, that the same type of failure (rubber off the brass/bronze hub) has been happening over a 3-4 year period? That would be one hell of a big batch of bad impellers to span that many years.
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post #25 of 36 Old 07-27-2013
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Re: Premature impeller failure cause

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Originally Posted by LinekinBayCD View Post
The blades of the failed impeller were fine, but the brass fitting/bushing and key pin had delaminated from the rubber bushing.
I have seen this condition twice and both times on new, never installed impellers. Judging by the boxes they came in, they had been sitting on the chandlers shelf for many years.

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post #26 of 36 Old 07-27-2013 Thread Starter
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Re: Premature impeller failure cause

I agree. We're trying to get Westerbeke to send a new pump to see if that is somehow causing the problem.
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post #27 of 36 Old 07-28-2013
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Re: Premature impeller failure cause

In my 7.5 Merc. 2 stroke the impeller failed after being test run in a 50 gallon barrel. The first time after being prepped by a repair shop, The second time I did it all by myself. The impeller aparently cannot stand the oil in the exaust. Now I always keep a spare impeller and the tools. They were both OE impellers.

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post #28 of 36 Old 07-28-2013
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Re: Premature impeller failure cause

Couple of things after reading this post... Check to see if new impeller doesn't delaminate by trying to pull the vanes at the 9 o'clock and 3o'clock position.

Flip the water pump cover and try the unused side.

Make sure the impeller has seated it self fully on the shaft.

Too much pressure from the cover on a improperly mounted impeller may cause excessive heat which in turn may cause premature failure..
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post #29 of 36 Old 05-27-2015 Thread Starter
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Re: Premature impeller failure cause

Fast forward to 2015. After another impeller failure in the summer of 2014 on my Westerbeke 55 I had enough of trying to investigate the cause of the annual failures. I bought a new pump, upgrading from the stock Johnson belt driven F35 to a Johnson F5 crank mount. My yard had an adapter plate fabricated so that the pump could be bolted the adapter plate which in turn was bolted to the crank pulley. The crank mounted pump has the added advantages of eliminating a belt and being 1000% more accessible for changing the impeller. Previously the pump had to be removed in order to change the impeller.

I sized the new pump so that it pumps roughly 1.5 time the GPH as the stock pump. Because of the size the difference between the crank pulley and the pulley attached to the pump, the water pump was spinning at 125% the engine RPM's. During the course of investigating what pump to use I learned that by changing the size of the cam in the pump the GPH can be increased or decreased. Although the new F5 pump probably pumps 2.5 times the GPH of the F35 at any given RPM I got it down to about 1.5 times (150%) the old GPH by using a different cam and the slower RPM due to being mounted on the crank.

The water flow is noticeably greater but not crazy more than with the old pump. The engine is running slightly cooler which is a good thing as it sometime would be over 190 degrees. Now seems to settle in at about 182-183 at cruising RPM's. If I make it through the summer without an impeller failure I'll know if this remedy was a success. At least now changing the impeller will be a 10 minute job.
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post #30 of 36 Old 05-27-2015
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Re: Premature impeller failure cause

I noticed on the Atomic 4 pumps that it was easy to end up with an impeller that is a little too wide for the casing, as well as too narrow. The cams wear down over time, and may even wear out the blades, if they have been damaged.
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