More Oberdorfer Raw Water Pump Info

[KZW]

There is a lot of discussion on swapping out the Sherwood G-908 raw water pump for the Oberdorfer N202M pump. The big advantage is the Oberdorfer allows easy access to the impeller. On the Sherwood, the entire pump must be removed to change out the impeller. The following is for the Universal (Westerbeke) M-25XPB engine on my 2005 C-310.

The Oberdorfer N202M-908 is a direct drop in replacement for the Sherwood G-908. The threads on the N202M-908 match the hose fittings on the Sherwood. Note that older versions of the M-25 use a Sherwood with a mounting flange. I don't know the part number for that Sherwood. The G-908 on my M-25XPB doesn't have a mounting flange, it uses two clamps, one one either side of the pump. The clamps bolt into the block. I'd prefer a flange, but that is not how my block is set up.

Picture 1 shows the Sherwood on my M-25XPB. If you look directly under the pump you can see the evidence of it leaking.

Picture 2 shows my new, just out of the box, Oberdorfer N202M-908. Note the absence of a flange. On the far right is one of the four bolts one extracts to remove the cover plate of the impeller. Easy access!!! Lubricate the impeller before first use. You will be glad you did!

Picture 3 is a close up of one of the clamps holding the Sherwood on my M-25XPB. Note the absence of a flange.

Picture 4 is the installed Oberdorfer.

The process is straight forward, even for folks like me me who have issues using tools (something always goes wrong). Remove the two hoses from the barbs. Yes, I marked mine port and starboard, although it would be very, very difficult to hook them up backwards. A hair dryer might help. Heat the hose, don't burn it. Mine were a PITA to remove. Remove the hose fittings from the Sherwood. You are going to reuse them. Remove the two clamps on the pump. One came out clean. The other required lots of PB Blaster, swearing, and some light tapping with a hammer. Be careful trying to torque these off. If you break them in the block, you are hosed. A mechanic friend drank beer and watched me work. He curtailed my enthusiasm to get a breaker bar to remove the @#! thing. Retain the bolts and clamps, you will reuse them. Remove the Sherwood. Inspect and clean the pump mount, as required. Put in the mounting gasket. Mount the Oberdorfer. Put in the clamps and bolts. Carefully torque down the bolts, alternating sides, and wiggling the pump to ensure it is seated. Reattach the hose fittings, attach the hoses and put on the hose clamps. Check to see if new hose clamps are needed. Fire up the engine and check for leaks.

Pump: Oberdorfer N202M-908
Gasket: Westerbeke 302678
Spare Impeller: Oberdorfer 6593K

The folks at Decopump.com could not have been more helpful!!!!!! If you are going to replace a pump, call them.

 

[Stu Jackson]

Nice work. That's an M25XPB? Somewhere in the text you said M25. Big difference.

Also, those who are considering this change should recognize it is a SIGNIFICANT upgrade, simply because of the materials in the pumps are different. This is above and beyond the simplicity of servicing the impellers.

 

[JK_Boston_Catalina310]

To avoid the fight with the bolts next time you have to remove the pump, I would recommend using some kind of anti-seize. I use Tef-Gel and Lanocote depending on the use.

Care to share the cost of the pump?

 

[njlarry]

Thank you both. Glad Oberdorf has come up with a "drop in" replacement. I have to replace my Sherwood this spring.
Stu is right about improved quality. My old pump failed after 90 hrs although to be fair the 90 hrs were spread over 3 years. Hopefully the Oberdorf will last a lot longer.

 

[KZW]

Nice work. That's an M25XPB? Somewhere in the text you said M25. Big difference.

Also, those who are considering this change should recognize it is a SIGNIFICANT upgrade, simply because of the materials in the pumps are different. This is above and beyond the simplicity of servicing the impellers.

The engine in my boat is an M-25XPB. My error in not typing in the full name throughout. I will edit the post.

 

[KZW]

To avoid the fight with the bolts next time you have to remove the pump, I would recommend using some kind of anti-seize. I use Tef-Gel and Lanocote depending on the use.

Care to share the cost of the pump?

I coated the threads with a anti-seize compound given me by my mechanic friend, but finished the tube and tossed it. I should have noted the brand. It is my fondest hope I never need to remove this pump.

Regarding the cost, grab your nitroglycerin pills, from Depcopump:

Pump $352.80
Spare Impeller $39.60
Gasket $1.30
UPS overnight $23.63

Not worrying about having to change a Sherwood impeller while underway: Priceless!


The Oberdorfer N202M-16 is about $75.00 less than the -908. I don't know if that flanged pump will fit the M-25XPB. There is no corresponding flat surface on my block.

I think the Sherwood could be rebuilt and reused. Not on my boat. I'm happy with the Oberdorfer. The engineer that designed the Sherwood, requiring pump removal to check the impeller, should be shot.

 

[KZW]

Thank you both. Glad Oberdorf has come up with a "drop in" replacement. I have to replace my Sherwood this spring.
Stu is right about improved quality. My old pump failed after 90 hrs although to be fair the 90 hrs were spread over 3 years. Hopefully the Oberdorf will last a lot longer.

I purchased the boat in July 2015. The Sherwood was original and the engine had 307 hours on it when I bought the boat and 342 on it when the pump was replaced.


BTW, it is 43 degrees here in the Florida panhandle. The Bay water temperature has dropped to 50 degrees. I know most of you are laughing, but this is a severe hardship for those of us living in paradise. I had to put a heater in the boat as the temperature dropped to 22 degrees last night; the boat is in the water and not winterized (because I plan to sail it this weekend!). I know you feel my pain. But then think about us in August when it is 97 degrees and 99% percent humidity.

 

[Stu Jackson]

KZW, you eventually WILL have to remove the pump. Here's why:

Oberdorfer Pump Rebuild 101 - http://c34.org/bbs/index.php/topic,6766.0.html

 

[KZW]

KZW, you eventually WILL have to remove the pump. Here's why:

Oberdorfer Pump Rebuild 101 - http://c34.org/bbs/index.php/topic,6766.0.html

Stu,

Well, it all depends upon:
- How long it takes the pump to fail again,
- How long I will be in sufficient health/have sufficient funds to keep and sail the boat,
- When a hurricane will arrive and take the boat,
- How long I live?

I wouldn't make book on which of the four occurs first.

 

[peter_ms]

My solution to the problem.
Original Sherwood "reliable" pump...
Friend with a machine shop...
My design; her machinery.
Milled the front face of the housing shy of the impeller
Fabricated an O-ringed cover plate and refastened the pump with studs... And nuts to fasten the cover plate.
Though they were doing it for free, I asked her to track the hours as I was going to patent it and go into business to solve a "universal" problem.
When they were done, she told me that I didn't really want to know how much it actually cost in shop time.
I run in fresh water so I wouldn't have some of your same reliability issues; but finished the 3rd summer on the modified pump...
Peter

 

[Capt jgw]

And when your buying spare impellers, don't get the blue Globe units. They don't pump, at least in a pump with any wear on it. I've tried them on three different older pumps, two Sherwoods and an Oberdorfer, and none of them worked. Globe days they last longer, actually they last forever because you won't be able to use them. I went back to the black rubber kind on all three pumps and they all worked fine.

 

[JK_Boston_Catalina310]

My solution to the problem. Original Sherwood "reliable" pump.

This is where your approach goes astray. The Sherwood is anything but reliable. Time after time we hear about new or rebuilt Sherwood pumps failing. The Oberdofer is just a much better pump.

 

[peter_ms]

Must be a salt water issue. 625 hrs and 13 summers on this one. Now the transmission! thats another story.
Peter

 

[Tom J]

This is where your approach goes astray. The Sherwood is anything but reliable. Time after time we hear about new or rebuilt Sherwood pumps failing. The Oberdofer is just a much better pump.

So true. My Sherwood failed, was rebuilt and failed again. I like my new Oberdorfer. Half the price of a Sherwood and I can change the impeller without disassembling the pump.

 

[Stu Jackson]

Tom's right. In all the discussions about the O vs S pumps, it is the materials of construction that makes the largest difference in the longevity of the pump. Take a look at the DEPCO website or even TOAD, which show blowups of the two pumps. The simpler O pump construction is simply far superior, salt water or fresh have nothing to do with it.

 

[JK_Boston_Catalina310]

Must be a salt water issue. 625 hrs and 13 summers on this one. Now the transmission! thats another story.
Peter

You have very low hours for a 13 year old boat. My guess is that you are going to have to deal with this pump very soon. Mine went at about 600 hours but that was at 11 years old.

 

[peter_ms]

Well I will have my fingers crossed; there is no basic difference now between my pump and the Obendorfer other than I have 3 nuts to remove instead of 4 capscrews. The gasket/O-ring plate is a non issue now that it's assembly is not part of trying to twist the new impeller and hoses into place at the same time as fitting all the little bits in on the back side of the pump. If anyone doesn't understand my comment about being essentially the same; look back a few posts to the pictures of my modified Sherwood.

At very worst; if mine does start to leak, I have at least delayed the inevitable long enough for Obendorfer to design that drop in replacement. That might have been my first choice had it been available 4 yrs ago.

Peter

 

[KZW]

In talking with Depcopump and investigating Sherwood vs. Oberdorfer I gleaned that unless it is from exiting stock, you cannot buy a Sherwood G-908 anymore. Many sites list the pump as discontinued. Sherwood still makes the same pump. They sell their entire output to Westerbeke, who puts their name on it and sells it. In checking prices I found that Westerbeke is very, very proud of their Sherwood made pump.

 

[c130king]

I posted on this issue back in April or May. Fried my Sherwood (forgot to reopen raw water valve...long story) so did some research and bought the Oberdorfer from DepcoPump based on some recommendations from here. But I didn't read enough and didn't realize it wouldn't work with out some modifications. Didn't have time, skill or capability to do those mods so called DepcoPump and returned the Oberdorder. They had Sherwood for like twice+ the price. But it works just fine.

But next time I will be better prepared...I hope.

Cheers,
Jim

 

[buddybear]

Why do you need to take the Sherwood pump off the engine

Purchased hull# 57 Catalina 310 2012 Universal M25XPBC, decided to change the impeller in 2014 after 600 Hrs. Took the pump off the engine and replaced impeller the pump looks like the in the manual and is stamped Sherwood didn't see any model#. After replacing the pump I looked to see why the impeller could not be replaced with the pump on the engine. With the pump on the engine I only need to take the 3 bolts which hold on the front plate from behind the pump take off the front plate pry out the impeller and replace. I did notice there was not a wearplate or circlip in the pump. Am I missing something maybe this not the original pump?

Thanks for any info
Have really enjoyed this boat and am learning the engine