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rebuilding Oberdorfer Pump

42K views 65 replies 19 participants last post by  eherlihy 
#1 ·
I am going to rebuild the Oberdorfer 202M-15 pump on my M25XP Universal. The pump kit comes with a carbon bushing that shattered when I removed the old one. Does anyone have experiance rebuilding this pump? I assume if I try and press it it will shatter, and I assume that I may need to Heat the pump body in the oven and freeze the bushing.

Anyone have experiance with this pump, or thoughts on it?
 
#33 ·
Actually Stu, your picture shows what I found most difficult about replacing the seals..


That carbon bearing, the black circle through which the Allen wrench is passing, will likely get trashed in the process.
Looking at your pic, I suspect that your bearing may be damaged...
 
#34 ·
I have a backup pump, too!

The carbon bushing is just fine. I checked both ends, and only the inner end is an issue anyway. It's essentially only a sleeve, so unless it's worn or actually cracked and broken, it ain't goin' anywhere and will support the shaft. I was very careful and actually used your idea for the nail for the inner seal.
 
#36 ·
Stu - Not meaning any offense, but; What is that crud on your timing case cover?:eek:
:eek:
 
#37 · (Edited)
None taken. You nailed it, it's crud. Seemed that the pump/engine gasket might have been leaking a tad, so the engine started to go all crud-dy on me. When the OEM pump started to go back in 1998 or 9, that whole section of the engine started to get rusted out. I painted it with Rustoleum gray primer, never did get to paint it in the Universal Bronze (have a can) also understand that GM Camel (#286) also works. As you can see from other pictures in that link, it's time to paint again.

It's truly amazing how salt water can "migrate" around.

A friend wrote this on our C34 Board:

When we first posted it the #286 GM Camel paint was available at Track auto stores (1998?). When Track was bought up, I guess that the metallic copper paint went with the buyout? Just look for some metallic copper auto paint.
BTW, the front of the accessory end of the engine (Oberdoffer/Sherwood and the internal water pump is mounted to) is an aluminum alloy!! The bell housing is also an aluminum alloy. The Hurth transmission body is also an aluminum alloy. The only part of the engine that can rust is the cast iron Kubota block and the steel oil pan.!
Don't get me wrong, because aluminum alloy will corrode somewhat if salt water stays on it. I have never painted my new injectors, because salt water should never get up that high. To preclude the chipping of paint you can also get the same protection from BO Shield (waxy) spray.
 
#38 ·
Going to re-activate this thread!

Rebuilt my OBD pump a few years ago. "Time to change the impeller" me thinks!

Noooo Problemo! Out with the old it; was still good but lost it's "spring" and the vanes were not coming back to straight. So we put the new one in. It's a globe "run dry" I also have a OEM spare. So get all together. it won't prime. Just like 3 yrs ago when I tried the Globe impeller! ARRRG Put the good OEM impeller in.. and it pumps! go figure the globe blue run dry looks identical in every way. but it won't prime and pump.

Looks like OBD pump impellers are going for over $30 now. just amazing what things cost for "marine" applications.

How could an impeller that's identical not work? My only guess is it's too soft? :confused:

yes, have the thin OEM paper gasket, no it doesn't drip water, seals are still good.
 
#39 ·
Did a search on sailboat owners and Maine Sail's Musing, Seems the Globe impellers are a problem. So I'll order another spare from Moyer or one of the others. Defender is $37 actually more then Moyer's at $33
 
#40 ·
D- Before you replace the impeller, you can coat it with dish soap and it will prime.
 
#41 ·
The black rubber impeller primed from the bucket in about 5 seconds E. The globe impeller is about 3/64ths too thin. It's pumping like a champ again!
 
#42 ·
Bronze fittings?

I'm replacing my Oberdorfer n202-15m pump and just wondering what fittings to use. I have a 3/8 NPT to 5/8 barb elbow and a straight 3/8 NPT to 5/8 barb nipple on the old one, I don't know if it is bronze or brass.

I read that brass fittings don't work well with bronze, and while buying fittings made of brass does not seem to be a problem, I'm not able to find any bronze fittings with 3/8 NPT anywhere.

Wonder what others used? Is brass ok? Plastic?
 
#43 ·
Brass is OK in this application, as it should be protected by your H/X zinc.
 
#46 ·
Re: My experience, and a few references

Thanks! I was checking the impeller on my 202m-7 and the same thing happened to me. I didn't miss the C-clip but the shaft came out when I pulled the impeller out. When I when to put the shaft back in, I had to wiggle it but it went back. It is an old pump and the gasket was all but gone...

On anther note, my O'day 34 has a manual bilge pump put no electric. I am adding one and probably two and m trying to figure out where to discharge. Thinking about a "y" connector into the manual pump discharge hose. Thoughts? where do you discharge?
 
#48 ·
Glad that my post helped!

I have since learned that the "C" clip is NOT NECESSARY! It was fitted by Oberdorfer to aid in shipping.

A quick answer to your question is that the bilge pump discharges through the transom. I suggest that you start a new thread, where I can give you a lot more detail.
 
#49 ·
I have since learned that the "C" clip is NOT NECESSARY! It was fitted by Oberdorfer to aid in shipping..
That explains something. I changed my impeller last week, and each time I have done it I wondered why there was the C clip. It just seemed to hold -- nothing! I always put it back since, after all, the engineers who designed it must have known what they were doing, who am I to mess with their design?!

So know I know!
 
#50 ·
Re: My experience, and a few references

Thank you for the thorough report! I have a question regarding priming of the water pump if needed.
I replace a fried impeller and gasket today, made sure all water sources/hoses are clear. Sealed everything up and still no water. I did confirm that the impeller shaft is engaged and spinning when the motor is running. Is there something I'm missing to prime the pump?
Thank you in advance. Mark
 
#51 ·
Re: My experience, and a few references

Thank you for the thorough report! I have a question regarding priming of the water pump if needed.
I replace a fried impeller and gasket today, made sure all water sources/hoses are clear. Sealed everything up and still no water. I did confirm that the impeller shaft is engaged and spinning when the motor is running. Is there something I'm missing to prime the pump?
Thank you in advance. Mark
One trick that I have used to get my pump to prime is to coat the surface of the impeller with liquid soap. This usually gets the pump to work right away.

The only time that this has not worked, was this year when working on a client's boat. I believe that something that my client did in the process of winterizing the pump on his boat created a leak in the pump housing. We solved this by simply installing a new pump, rather than chasing our tails endlessly. 20 minutes later the new pump was installed and everyone was happy.
 
#52 ·
I appreciate your quick response. I read on the forum to coat with soap prior to installing the impeller also which definitely helped getting it in. I'm going to try to connect the water source hose direclty to the water pump intake to take out the filter and associated hoses. It's perplexing, I know I'm getting pressure in the pump due to the amount of air coming from the out put of the pump with the 'discharge' hose disconnected and the amount of pressure I see. It's a pretty simple mechanical system which is why I'm perplexed. If it doesn't work connecting the hose direclty, I'll order a new water pump. however, my pump base looks nothing like the one in the future above. It looks like there are only 2 connecting bolts. I can send pictures if there is a way. Thanks again.
 
#53 ·
mpoisson,

What make and model engine are you working on? Several different Oberdorfer pumps were used on several different make and model engines. Most references are to a MN-202-15 used on a Universal M12/M15/M18/M25/M30/M4-30/M35/M25-XP/5411/5421
 
#54 ·
Mark, when I replaced the impeller on my Oberdorfer on my Atomic 4 the first time, I made my own gasket from gasket material I purchased from a local auto store - big mistake. The pump would not prime. I called Moyer Marine and told them what I did, and right away they solved the problem. They sold me a replacement gasket that was only about the thickness of a single sheet of paper. I installed the new gasket and the pump worked like a charm.

Here is the pump I have:



Hope this helps,

Gary :cool:
 
#55 ·
Thanks Gary, glad to hear that the gasket fixed the problem. My new impeller came with a paper gasket. I ordered from Catalina Direct and both fit perfectly. You now have me wondering though. When I removed the old impeller, there was no gasket at all, only what ever sealant the last owner used. I do have another question. What is the proper position of the adjustment/valve on the underside of the pump?

Thanks for the picture, it is a match for what I have.
 
#57 ·
Thanks Gary, glad to hear that the gasket fixed the problem. My new impeller came with a paper gasket. I ordered from Catalina Direct and both fit perfectly. You now have me wondering though. When I removed the old impeller, there was no gasket at all, only what ever sealant the last owner used. I do have another question. What is the proper position of the adjustment/valve on the underside of the pump?

Thanks for the picture, it is a match for what I have.
Then it would appear that you have an N202M -03 or -07



If your pump has a groove machined into the body, then it is a N202 pump and you use a rubber gasket (#3 in the diagram above). If not, it is a 202 pump, and it uses a paper gasket. There should be no "sealant" other than one of these gaskets.

That "adjustment" is a plug, that can be removed to prime the pump (if you can get water into it).

I suggest that you simply call Depco, and order a new pump.
 
#58 ·
Good news....it looks like it's fixed. I took the raw water hose and ran directly to the water pump and it primed the pump quickly. Re-assembled the rest of the system, ran to the pump dock and back and she maintained 165 degrees. Note, I'm in Arizona and it around 108 outside right now. Thanks for all of your suggestions.
 
#60 ·
I found a better source for the O-ring for the N202M pump! Amazon carries these: "034 Viton O-Ring, 90A Durometer, Round, Black, 2-1/8" ID, 2-1/4" OD, 1/16" Width (Pack of 10)." Total cost (shipping & tax included) is <$10 for TEN!!!
 
#61 ·
Update: I have been running without the pesky circlip for the last 6 years. Last year I brought my boat from RI to FL and back to RI (Florida was not all that I dreamed it would be). That's over 1000 hours on the pump with NO ISSUES. You must have the 2 copper washers on the impeller, one forward, and one aft, and the pump works great, and you don't need circlip pliers to remove the impeller if the need arises.
 
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