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Old 10-23-2021, 12:06 PM   #1
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Buggered Impeller.

Gee. Maybe this is why the engine always ran a little hot?
New to me 1980 CHB PT-38 With a single Ford Lehman,so i decided to do all the preventative maintence I could not do last season.
This certainly doesnt look good to me .
Going to check with American Diesel to see if the pump itself should be replaced but welcome advise from here as well.
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Old 10-23-2021, 12:09 PM   #2
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AD has an upgraded water pump for the 120s. I would ask Brian.
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Old 10-23-2021, 12:39 PM   #3
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Originally Posted by Craig_b View Post
Gee. Maybe this is why the engine always ran a little hot?
New to me 1980 CHB PT-38 With a single Ford Lehman,so i decided to do all the preventative maintence I could not do last season.
This certainly doesnt look good to me .
Going to check with American Diesel to see if the pump itself should be replaced but welcome advise from here as well.


The pump body and cam look good to me! It looks like someone installed the last cover with silicone sealer, not a paper gasket. The paper gasket is an important part. It is what spaces the cover out properly from the body to make the clearance at the ends of the impeller correct.

If the cover plate is not scored or worn excessively I would reassemble with the proper impeller and paper gasket.

Bill
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Old 10-23-2021, 12:57 PM   #4
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Looks like you got it just in time. All the pieces look to be there. If no scouring just replace the impellor.
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Old 10-23-2021, 01:26 PM   #5
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I disagree about the cam plate.
The photo is not great but it looks like several of the fingers of the cam plate are worn to the point of being sharp. THey will begin to cut the impeller reducing its pumping ability.

In addition the wear will have reduced the thickness of the cam plate itself which means the pump cannot move as much water as intended.
Get a new cam plate.
I suggest that the back wear plate also be closely examined for excessive wear as it to will reduce water pumping ability if worn to far.

As far as the replacement pump from A.D. that has proven from all accounts to be a good move. More reliable drive and by the time you get into cam plate replacement and maybe the rear wear plate you may have run the cost up enough to help make the Johnson a whole lot less of a shock.
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Old 10-23-2021, 02:10 PM   #6
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I disagree about the cam plate.
The photo is not great but it looks like several of the fingers of the cam plate are worn to the point of being sharp. THey will begin to cut the impeller reducing its pumping ability.

In addition the wear will have reduced the thickness of the cam plate itself which means the pump cannot move as much water as intended.
Get a new cam plate.
I suggest that the back wear plate also be closely examined for excessive wear as it to will reduce water pumping ability if worn to far.

As far as the replacement pump from A.D. that has proven from all accounts to be a good move. More reliable drive and by the time you get into cam plate replacement and maybe the rear wear plate you may have run the cost up enough to help make the Johnson a whole lot less of a shock.

The plate on the back has Johnson stamped into it. Does that mean this is already the upgraded pump?
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Old 10-23-2021, 02:27 PM   #7
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I would ask Brian, he will know. If it is the newer style pump that is very good.
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Old 10-23-2021, 04:31 PM   #8
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Also, check that the shaft turns smooth, no rough spots.
If rough, bearing and seal will need replacement.
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Old 10-23-2021, 05:03 PM   #9
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Quote:
Originally Posted by C lectric View Post
I disagree about the cam plate.
The photo is not great but it looks like several of the fingers of the cam plate are worn to the point of being sharp. THey will begin to cut the impeller reducing its pumping ability.

In addition the wear will have reduced the thickness of the cam plate itself which means the pump cannot move as much water as intended.
Get a new cam plate.
I suggest that the back wear plate also be closely examined for excessive wear as it to will reduce water pumping ability if worn to far.

As far as the replacement pump from A.D. that has proven from all accounts to be a good move. More reliable drive and by the time you get into cam plate replacement and maybe the rear wear plate you may have run the cost up enough to help make the Johnson a whole lot less of a shock.
where are you seeing sharp edges? would there not be cut marks on the impeller blades from the fingers?
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Old 10-23-2021, 05:32 PM   #10
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Can anyone tell me where i could get just the impelller just in case thats the route i go?
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Old 10-23-2021, 05:41 PM   #11
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I usually get them online, google the part number. Get it from a place that you think sells a lot of them so they havenít been sitting on the shelf for a couple of years. I got my last ones from Defender I think.
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Old 10-23-2021, 05:58 PM   #12
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I usually get them online, google the part number. Get it from a place that you think sells a lot of them so they havenít been sitting on the shelf for a couple of years. I got my last ones from Defender I think.
Any idea what the part # would be?
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Old 10-23-2021, 06:02 PM   #13
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Any idea what the part # would be?
Craig, it is in the picture of post 1.
Johnson 1028
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Old 10-23-2021, 06:16 PM   #14
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Craig, it is in the picture of post 1.
Johnson 1028
Is there another way to determine it just in case it was the wrong part installed last time?

I have no faith in whoever has done previous work on this boat.
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Old 10-23-2021, 06:19 PM   #15
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Call Brian at American Diesel. He will know. Usually Mondays are not a great day to call though.
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Old 10-23-2021, 07:33 PM   #16
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Is there another way to determine it just in case it was the wrong part installed last time?

I have no faith in whoever has done previous work on this boat.
Fred Warner website
Product Description
New Jabsco Profile Y impeller kit. Part number 17937-0001-P. Used by many major engine builders. See table for part number cross reference.

Cross Reference Part Number
Yanmar 127610-42200
Perkins 0460024, 24880031
Volvo 801277, 877061-2, 825941
CAT 7C-3286
Johnson 09-1028B
Sherwood 18200
Oberdorfer 7441
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Old 10-23-2021, 08:01 PM   #17
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I have a different engine with a different pump. But I had to do exactly those replacements about 5 or 6 yrs ago and it made me VERY watchfull of wear in those areas. It took a lot of years to get to that point but get to it it did.

I also replaced the drive shaft this last winter due to wear of the splines that drive the impeller.

I always do a complete pump re/re including the rotary seal and bearing, all seals and gaskets but every 4-5 yrs for those.

That cam plate may be OK. The centre finger is the first to give trouble as the impeller fingers can bend in. As mentioned it is also a sign of the plate wearing. As thickness is lost pumping can be affected.

Cannot really tell from the photo but it is something to check which is why I brought it up.

If you talk to A.D., Brian , he should be able to give you the plate thickness and the wear point that it needs to be changed. Same for the back wear plate.

If the pump is the Johnson upgrade then maybe there is less to do as it will be much newer.
Just take your time and examine, examine and questionable bits replace.
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Old 10-24-2021, 08:45 AM   #18
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This is what I used on mine this year. Also replaced the cover plate because it was worn enough to feel and see the ridge.
Jabsco Wearplate & Cam Kit 7884-0000, Wearplate & Cam Kit https://www.amazon.com/dp/B00H8SSDQU...ing=UTF8&psc=1
The cover plate you took off hopefully was the original with the pump name and number on it. If it's the Jabsco then I recommend this kit. You'll have to remove the pump to get at the cam screw. Easy, two bolts and a nut holding it to the engine. Best to order a gasket in advance. The only hassle is cleaning the mating surfaces of the old gasket material.
Your hoses into and out of the pump need to be inspected for impeller bits. There may have been prior impellers that broke up.
My engine runs a steady 10 degrees cooler than before since replacing the cam, cover, and wear plate.
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Old 10-24-2021, 10:43 AM   #19
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Just ordered this impeller for my pump. It's a replacement for a 1027B , but that's the part number my old one had. I don't know what the difference might be between it and a 1027B.

I found getting at the little cover screws and keeping them from falling in the bilge to be a bit of a pain. So I ordered these stainless "cabinet screws" to replace the originals. Only fingers required to remove the cover.

My cover plate was worn a little, but I just milled it down on a diamond whet stone.
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Old 10-24-2021, 12:27 PM   #20
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A worn cover plate with a ridge can be easily corrected with a bit of 320-grit wet and dry sand paper, a FLAT surface and enough water to keep things wet while you rub it around on the sand paper. Never had a problem with doing it on both the original pump bodies and the Johnsons after I updated on my Lehamn 120s. The I switched to the wonderful o-ring sealed Speed Seal cover plate which unfortunately went out of business.
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