Sherwood Water Pump replacement with Oberdorfer on M25XPB

KWKloeber · May 05, 2017, 05:54:35 PM

Quote from: kwaltersmi on May 05, 2017, 05:33:03 PM
I launched today with my M25 XPB and the Sherwood pump is leaking. After opening it up to check the impeller, it looks like the rubber on the seal (Parts 10 through 12 - 30288X) was torn and was coming out. It dripped about 1 drop every 2 seconds at idle on launch, but quit dripping altogether once I was underway for the 3 mile motor to my marina. No dripping when I arrived at my dock.

So...

Should I replace the seal in the Sherwood pump? Is this difficult to do? Should I swap in the Oberdorfer (is it 908?) pump instead? Should I leave it alone and wait for it to leak again even though part of the rubber from the seal came out of the pump when I opened prior to motoring to my marina?

There's only one "correct" answer.... YBYC, but.......... see below if you even consider keeping a pump that is designed to seize up...

kwaltersmi · May 05, 2017, 06:06:32 PM

Ok, got it. I should replace with the Oberdorfer. But is the N202M-16 a direct replacement for the Sherwood on my M25XPB? Or do I need the N202M-908? Or something else?

KWKloeber · May 05, 2017, 08:23:01 PM

Quote from: kwaltersmi on May 05, 2017, 06:06:32 PM
Ok, got it. I should replace with the Oberdorfer. But is the N202M-16 a direct replacement for the Sherwood on my M25XPB? Or do I need the N202M-908? Or something else?

The 908 replaces the Sherwood. Unfortunately at a way overpriced cost. Or the -16 if you want a bolt on and aren't afraid to do the mod to the pump base. If you go thru the other thread I discuss trying to do a direct replacement bolt on. We did one, but now that Ob sold out to the big boys, they won't sell an undrilled base pump only in lots of 10 or 15 and at a premium price.

Ken

kwaltersmi · May 10, 2017, 05:30:45 AM

I ordered the Oberdorfer N202M-908 from Depco and will be doing the install this weekend (if it arrives in time). Thanks for the input.

KWKloeber · May 10, 2017, 07:35:26 AM

Darn could've saved you a few bucks over Depco. Anyway, I would recommend instead of replacing the bolts holding the Sherwood clips, getting two double ended uneven thread studs (M6 x 1.0 around 30mm long) and nylock flange nuts, and lock-tighting studs into the pump land on the gear case. With the rather crappy metal of case, I don't like torquing bolts into it. Just a little safety measure if you need to remove and service the pump. With my pumps I supply a n/c stainless steel stud/nut Kit, but you can't buy those on the street, you'd have to use steel.

You need to file down the "inside" side of the square hub of the large (7/8 inch) hose barb elbow so that when installing the pump you can turn the other elbow past the large one. The OB pump ports are slightly closer together than the SW ports so there's an interference when you install the elbows. I file down to the point where the square hub is level with the hose barb extension. Unfortunately there's no elbows made directly to fit this that you can double clamp, but every time I put my hand on a hose clamp I replace it with an ABA or AWBA brand solid (not perforated) band. It would be a good investment - I've replaced every clamp on my boat ;-)

I'll try to find my picture of the hose barb elbow mod and post it for you when I get on my laptop.

kwaltersmi · May 10, 2017, 08:29:31 AM

Thanks! I think I saw the hose barb mod photos in the Wiki. Do you know the size of the hose barb fitting? I might see if I can buy a new one and do the mod at home before I travel out to the boat this weekend for the install since I won't have access to a grinder while at the boat to mod the existing barb fitting.

KWKloeber · May 10, 2017, 09:19:45 AM

Here's the mod you need to make (pic 1). File down the hub on the larger elbow so it's even with the barb leg.
SLIGHTLY round off the end of smaller barb so it just turns by the larger hub.

I believe the wiki photos are for the M-25/XP elbows (slightly different than ones on the B series engines.)
I've seen the 1/2 npt x 7/8 elbow ONLY from Westerbeke, about 20 boat bucks. I did the one shown via Dremel - easy peazy.

Unfortunately they are brass not bronze.

While off, look inside the pump land with a bright light to make sure you have a reinforcing ring on the outside the camshaft fork (pic 2).

There's ways to install elbows that can be double clamped, not so elegant but the installs i did have worked very well (so far) pic 3. Notice it's my bolt-on flange mod, not clip-on 908 pump (will post a completed job pic later.)

kk

Bill Shreeves · May 11, 2017, 06:32:26 PM

QuoteI would recommend instead of replacing the bolts holding the Sherwood clips, getting two double ended uneven thread studs (M6 x 1.0 around 30mm long) and nylock flange nuts, and lock-tighting studs into the pump land on the gear case.

Ken,
I ordered the 202-16 for my M25XPB a while ago and I planned on installing it this weekend. I noticed the nugget of info above and I'm wondering where to get double ended thread studs M6 x 1.0 around 30mm long? I've seen some online but they're shorter than what you suggest. Also, I'm not sure what you mean by "lock-tightening studs". I'm still on the hard so, I'll probably fit and temporarily mount with the old bolts and replace with what you recomend before the splash.

KWKloeber · May 11, 2017, 06:43:30 PM

Bill

-16 pump? That doesn't fit the xpb without the major base mod and redrilling.

Finding them is the rub. I first got a set at a well stocked hardware store for the testing. Then had to special order all in stainless. McMaster-Carr might have them in onzie twozies.

I'll measure the min length you need and repost. The critical length is on the long side uneven thread. If you are using the -26 pump they can be shorter-- as they don't need to accommodate the Sherwood clips, only the thickness of the pump base.

Need to use lock tight on the threads so the studs don't back out when turning the nuts.

kk

Bill Shreeves · May 12, 2017, 11:57:33 AM

Quote-16 pump? That doesn't fit the xpb without the major base mod and redrilling.

DOH, that's extremely disappointing. I bought it from CD and the salesperson said the mod was pretty straight forward. Apparently not. So, I not only need to grind a considerable amount off the base, I also need to drill a new hole for a stud/bolt. I guess there was confusion regarding the engine I have. I now see at the end of the "Replacing a Sherwood Water Pump with an Oberdorfer" article how extensive the mod is. Well, I guess I'll have to get the Kubota gasket p/n 16264-88130 and the studs, nuts etc... Wasn't figuring on all that.

QuoteNeed to use lock tight on the threads so the studs don't back out when turning the nuts.

Everything is right-hand thread so it should tighten when installing the pump, correct? Heck, if the right size studs are difficult to find I suppose I'll wind up going with bolts anyway. Is there a significant advantage the studs over bolts?

KWKloeber · May 12, 2017, 01:29:50 PM

Bill,

Yeah major minor mod. along with a new hole, one needs to be enlarged (ovaled sideways.)

What's key is that there's no adjustment with the bolt-on, and the hose run is tight by the alternator, so positioning the "new" holes gets dicey. The one is close, but not right on and when oy enlarge it, it ends up very close to the edge of the pump flange.

I have some "beta" templates on CAD for the pump positioning -- my purpose was to make these from pumps with undrilled bases. I can't attest to the absolute accuracy of the template because Ob hadn't cooperated so well in supplying the pumps -- but it might help you?.

I used to use that Kubota gasket on the 908 pump installs but either it or the Wb gasket for the Sherwood will work. The Ob is a better gasket than the trashy Wb paper. But it might not seal as well, if that doesn't sound contradictory. With the Kb gasket, both the pump and the Sw clips sit against the gasket. With the Wb gasket (circle) only the pump is against the gasket. I can mail you one for a template if you need it?

A thought -- why not see if CD will take back the m-16 to CD (since they led you astray in the first place) in favor of a m-908? ($$$).

The original Kb old" gear covers came with studs!

ken

KWKloeber · May 12, 2017, 01:44:27 PM

This was the beta test of the XPB bolt on with the double clamp-able fittings, it works fine and keeps onapumping, but would be better if rotated like 1- 2° CCW.

If you zoom in you can see the stud, flange nut and enlarged hole in the base. To rotate it CCW that hole would need to be more oval

Need to use lock tight on the threads so the studs don't back out when turning the nuts [to remove the pump for service.]

kk

Bill Shreeves · May 12, 2017, 02:03:16 PM

I was thinking about trying to returning it for the 908. I guess with that one, since the base is round, you can rotate to obtain better clearance from the belt? Trying to get things wrapped up to launch by memorial day and this isn't helping. I'm thinking I might put the Sherwood back on while I sort this out. Nothin' ever simple, eh?

KWKloeber · May 12, 2017, 02:41:54 PM

It's not the belt, it's the alternator itself and the 7/8" Hx hose.
Ridiculous that Westerbeke used a 7/8" inch hose for that, should have been a 5/8" barb on the Hx inlet.

KWKloeber · May 12, 2017, 02:50:11 PM

We could've gotten the alignment spot on the first time, but we were doing this beta with a boat in VA, me between NC and NY, and the pump machining in GA. I didn't have an XPB that I could run down to and check so depended on photographs being spot on and vertical to get the angles all set for my CAD drawings. I believe the pump needs to be exactly 45° CW from vertical. Give or take a fudge factor.

ken