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Old 07-27-2022, 09:39 PM
Golfdad75 Golfdad75 is offline
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Obendorfer pump

Are all Obendorfer pump model 202m7. The only number I can find on my pump is 8595. Is there any trick to rebuilding it.?
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Old 07-28-2022, 09:43 AM
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Depending on cavity wear, it may not be rebuildable. Sure, bearings, seals and shaft are all replaceable but if the cavity in which the impeller spins is worn to a point where there is no longer a good seal on the edges of the impeller vanes, the time has come for complete pump replacement.
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Old 07-28-2022, 12:26 PM
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How would I know

Is there anything to tell me that
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Old 07-28-2022, 01:27 PM
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The biggest issue is it won't prime/pump anymore. If you need to replace, I highly recommend the Moyer 502 pump..it moves way more water than my 202m3 did.

Throw up a picture, someone here can probably identify it. The difference between the 202m3 and 202m7 I believe is the size of the "shoe" in the cavity..the 7 has a bigger shoe and in theory pumps more water. Also check the inside of the plate...that should be smooth, and a worn pump will have noticeable wear from the impeller.
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Last edited by sastanley; 07-28-2022 at 01:30 PM.
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Old 07-28-2022, 07:39 PM
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I took the pump to a marine pump guy and he said to just replace the seals. He also told me that I probably was my own worst enemy, I put too much grease in. He told me 1/2 pump every 6 months with a 10 oz gun. I blew the seals out.
In the last 10 days I have put in a new rwc impeller, rebuilt the starter, new solenoid, new hoses to the rwc, cleaned the strainer and dropped the carburetor and cleaned it. Now new impeller and seals in the fwc. I am hoping for a respite. But I have to admit it has been pretty reliable until now.
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Old 07-28-2022, 07:55 PM
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Those old Oberdorfer 202 pumps DO wear out. I fought with one for years - new shaft, new seals, etc. I figure time working on the pump is time I could spend sailing. Get the new Moyer pump and enjoy your life.
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Old 07-31-2022, 05:54 PM
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Quote:
Originally Posted by Golfdad75 View Post
Is there anything to tell me that
Using a dial caliper measure the width of the impeller and the depth of the pump cavity. Subtract the latter from the former. If the answer is negative the pump is done.
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Old 08-01-2022, 12:01 PM
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Thanks one more question

Thanks for that information. After replacing the seals it runs about 130. Previously it ran at 160. If I use a infra red engine thermometer do I shoot willy nilly or are there certain spots to check.
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Old 08-02-2022, 08:36 AM
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I've attached one of the worksheets we used during the testing of the Moyer Marine thermostat showing all the temperature measurement locations.
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File Type: pdf A4 temp worksheet RWC with Tstat.pdf (33.2 KB, 153 views)
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Old 12-01-2022, 08:45 PM
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Post Parts interchangeable for Oberdorfer models?

Continuing in the same logic as the original post...

What is the difference between the Oberdorfer 202m7 (or m3?, etc...) and the Oberdorfer 201? How can they be distinguished by the first time pump puller? Most importantly for rebuilding purposes?

I need to rebuild my pump (I am not ready yet to spring for new) and I see Moyer Marine sells a rebuild kit for the 202m7 and backplate gaskets are available for 202m7 or Oberdorfer 201 pump. Is that because perhaps the shaft and seals etc.. are interchangeable?

Are there other Oberdorfer pump models to be considered besides? My pump clearly says Oberdorfer, but I have not yet discerned other helpful markings. I don't want to pull it until I have the parts in hand because my boat is still in the water.

Last edited by JustinAlenScott; 12-01-2022 at 08:47 PM.
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Old 12-02-2022, 12:35 AM
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Thumbs up

Justin, As I understand it, the only difference between the 202m3 and the 202m7 is the size of the "shoe"...on the 202m7, the shoe is thicker which in theory forces more water thru the pump outlet.

Other considerations (the route I took)...get the Moyer equivalent. I replaced my 202m3 with the 502 flange pump that mounts on the back of the motor and it moves WAY MORE water than my old 202m3. It is pricey, but worth every penny, IMO.
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Last edited by sastanley; 12-02-2022 at 12:40 AM.
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Old 12-12-2022, 12:49 PM
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Oberdorfer rebuild

Last spring while I had the copper stand pipe muffler out for rewelding, decided to pull the original (from 1974) Oberdorfer pump out, and purchased the Moyer rebuild kit, as it looked like there was no slop in the pump, just some leaking from the seals. Only had one issue with punching the original seals out, but Don talked me through it. The Moyer extension bolt for the lower pump bolt hole is definitely worth the money.

Replaced the original cam shoe with the thicker one, and it certainly increased the water flow! So much so (was running original thermostat, soaked in white vinegar, with the Moyer bypass kit, operating temp was always in the desirable 160-180F range) that this short season (maybe 30 engine hours total) the temperature never went above the 130-140F range, which produced more water condensation in the oil than I thought was good.

Also discovered when pulling the (new at the start of the season) impeller for inspection at winter layup, it appears that the extra vane compression produced by the wider shoe also greatly reduced the life of the impeller, with cracks showing on all the vanes-I doubt whether it would have held up for another ten hours, while I used to get two or three years out of an impeller before. Definitely install will a new impeller in the spring.

I'm going to put the thinner shoe back in next spring, and see what happens.
Given the difficulties with thermostats over the years, and my experience last season, I'm hoping the thinner shoe will restore proper operating temps and much longer impeller life.
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Old 12-13-2022, 02:48 PM
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Thick shoe vs. thin shoe, my two cents.

Get comfortable, this may take a while. Over the years I have used most of the popular brands of flexible impeller pumps and they have all worked quite well. Almost without exception they all had relatively thin shoes. When I came into possession of an Oberdorfer "thick shoe" pump I decided to test the flow rates of both styles. The thick shoe version definitely pumped more water but seemed to put more load on the electric motor I was using for the test. Because my fresh water, two "thin shoe" Oberdorfer pump system was working just fine, I decided to leave it alone. In the case of an A4 where the block and manifold water flow may be compromised due to "old age buildup", a thick shoe pump may be just the ticket to improve overall cooling. On the negative side, while looking from a design perspective, there are two things that seem to be in play here. First, the amount of "extra flexing" that the vanes are doing in a thick shoe model, and the extra amount of "side load" on the bearing surface of the main shaft. In the case of the Moyer roller bearing pump, this side load is probably not an issue, but in a standard "bushed" Oberdorfer, it stands to reason that pump body wear would be accelerated. Hopefully, my comments will shed a little more light on these cool little pumps.
Happy Holidays, Tom
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Old 12-13-2022, 08:14 PM
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Thumbs up Good point Thatch

Increasing the water flow and or pressure to get the water temp back to where it was is not fixing the problem, it is only masking it not "fixing" it.

Dave Neptune
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