Sherwood Redux

Stewartn · October 19, 2012, 05:22:55 AM

To those of you who have a 35B with the OEM Sherwood raw water pump. Put Desiree up for the winter yesterday and noticed some rust stains on the engine mat. Traced up the front of the engine and, sure enough, the raw water pump is weeping. Now, this is the third, 3rd, pump since 2009. It failed my second season with the boat in 2009 and was replaced with OEM new. That pump started to weep in 2011 and was replaced, new again, with about 100+ hrs on it. That brand new, OEM, replacement is weeping as of yesterday with much less than 100 hrs. Pumps were installed by competent mareine diesel mechanics. Impellers have been changed at once a season in the Spring. Other than this, Desiree motors like a clock. There no other problems. This is a PIA. I've a got new replacement to use, but what is wrong. I think this is a symptom and I would like to get at the cause. Pump shaft alignment, bad pumps, bad seals: any ideas for me to persue gratefully appreciated. Thx all.

Stu Jackson · October 19, 2012, 08:10:10 AM

The answer is the choice of pump: Sherwood. It has more parts and different materials and tends to leak way, way, way before the Oberdorfer pumps do. Switch to an Oberdorfer and get 5+ years out fo it before you even have to start thinking about new seals.

Ron Hill · October 19, 2012, 09:30:24 AM

Stewart : When you get a chance give me a call and I can answer some of your concerns.

The end of August, I rebuilt my M908 Sherwood. I believe I have identified the "weak link" and know how to fix it to extend the life of the water side.
On either the Sherwood or the Oberdoffer pumps the oil side is seldom a problem.

As always there will be an article in the Mainsheet Tech notes. Stay tuned

Jim Hardesty · October 19, 2012, 10:22:44 AM

Stewart, My Sherwood hasn't had any problems. May be luck. One thought, winterizing, I use the green -100 deg. in the engine (now the AC also) and the pink -50 in the water systems. Was told years ago, that the green had more corrosion protection and was better for rubber. I know many use the pink with no problems. Jim

lazybone · October 19, 2012, 04:25:52 PM

Mr. Sherwood also made me pull my hair out.

Mrs. Oberdorfer is your very bestest friend.

Jack Hutteball · October 19, 2012, 10:36:57 PM

Stewart, I am on my 4th pump in 11 years, about the same as you. I was told by a mechanic here that the fact I only put about 60 hours a year on our engine that salt and dirt particles build up around the seals while sitting idle. More to wear them away when running. His opinion. I am currently waiting for the shoe to drop on the current one. Probably sometime during the winter when I run the engine. We are in the water all year here so I run the boat at least once a month.
Jack

Stu Jackson · October 21, 2012, 04:39:31 PM

While Ron's "teasing" you about waiting for the next Mainsheet magazine, you might want to simply be aware of everything we have known, since 1987, about these pretty crappy pumps.

They leak, they don't "suck", they do "suck" and they rot out quicker than mayonnaise in summer sun and heat.

Here's a link to our own C34 Tech wiki, which explains why some skippers with even newer engines changed to Oberdorfer pumps.

http://www.c34.org/wiki/index.php?title=Replacing_a_Sherwood_Water_Pump_with_an_Oberdorfer

Can you see the trend here???

Stewart, you did me a great favor in reminding me to "watch my engine when it's running" which contributed to an important "Critical Upgrades" post.

KISS (the last S is for Stewart!:D), swap out your pump.

Ron Hill · October 21, 2012, 05:25:50 PM

Thanks Stu, as I've been ~~reminding people~~/ pleading with them since the early 1990s to LOOK at their engines while they are running!!!!!! You'd be surprised what you may find !!

Look in the critical updates and make sure that the Oberdoffer shaft mates with the engine shaft and you don't have a shaft mating mismatch - as Westerbeke had when they had to come out with a fix!

Other than pumping less water the Oberdoffer is a good pump. Pumping less water is a fact, not just BS.

When in doubt listen to someone who has had personal experience with only one of the pumps!

A thought

Stu Jackson · October 21, 2012, 05:59:49 PM

Quote from: Ron Hill on October 21, 2012, 05:25:50 PM
1. Thanks Stu, as I've been ~~reminding people~~/ pleading with them since the early 1990s to LOOK at their engines while they are running!!!!!! You'd be surprised what you may find !!

2. Look in the critical updates and make sure that the Oberdorfer shaft mates with the engine shaft and you don't have a shaft mating mismatch - as Westerbeke had when they cane out with a fix!

3. Other than pumping less water the Oberdorfer is a good pump.
When in doubt listen to someone who has had personal experience with only one of the pumps.

1. Stewart and I agree.

2. The Critical Upgrades we keep referring to is the "sticky" topic on the Main Message Board. Simple to fine. PLEASE, if anyone does NOT know what this reference is, PLEASE, PULEEZE, let us know. Now...

3. This BS about the Oberdorfer pumping less water is just that. BS. Look at it this way: If you had a pump that would die, just DIE, on your important raw water cooling system and compared it to another pump that MAY, just may, pump a tiny smaller amount of water but has worked on thousands of the same engines as yours and HASN'T FALLEN APART AND LEAKED, which one you choose?

For goodness sakes, I've run an Oberdorfer on our M25 since I bought the boat in 1998, it had that same pump body on the engine since I bought it. I replaced the entire pump in 1999 for $200 because I was too uninformed at the time to rebuild it. Instead of spending $20, I spent $200 for a new pump. I didn't need to. I finally got smart and learned how to rebuild the same Oberdorfer pump, and, like Ron and thanks to Ron, I, too, wrote it up for everyone to read. Here: http://c34.org/bbs/index.php/topic,6766.0.html

It's always "Your boat, your choice."

In this case, here's what you REALLY have to deal with:

--- A Sherwood pump that INHERENTLY by its own design is inferior

--- A Sherwood pump that by its own design has too many parts that either don't work or will fail

--- A Sherwood pump that by its design requires contortions to remove the faceplate to service the impeller

--- A Sherwood pump that, even by even Ron Hill's input will NOT allow buying at a discount price

--- compared to ---

A simple Oberdorfer pump that:

- works

- doesn't leak prematurely

- can be serviced easily

- can be replaced or rebuilt for far less $$

- are essentially discounted at www.depcopump.com

Golly ::::

What a choice.

PS - My engine hasn't ever overheated with my Oberdorfer pump. I've replaced my impeller "on the fly" from the four simple screws ON THE FRONT of the faceplate.

If someone wanted to sell you a Pinto, cheap, would you still take it?

Skippers with M35 engines have replaced their Sherwood pumps.

Why wouldn't you choose to do so?

OK, OK, there must be folks out there who think Sherwood pumps are just fine.

Just my choice, but NOT on MY boat.

Your boat, your choice.

TonyP · October 22, 2012, 12:50:53 AM

We have a Johnson (Sweden) pump on our 92. It works well and has for quite a while apparently and seems easy to service.

Does anyone else have these pumps .
I only ever hear of Oberdorfer and Sherwood on Catalinas?
cheers
Tony

Ron Hill · October 22, 2012, 07:03:30 AM

Guys : Before anyone makes the change from Sherwood to Oberdoffer; I'd recommend that you atleast talk to Joe Joyce Westerbeke Service manager.

Your boat your choice.

Roc · October 22, 2012, 04:53:28 PM

Interesting note from Joe Joyce on pump capacity.

http://downeasteryachts.com/info-index/engine/universal-engine-info/universal-5432-raw-water-pump

Ron Hill · October 23, 2012, 03:29:53 PM

Roc : Thanks

When you have a larger pump cavity and more impeller blades and the pump is turning at the same RPM, that pump will pump more water -- than the smaller cavity pump, same RPM, with less blades!!

That's not BS, it's just simpler than Engineering 101 (High School Physics) !!

Stu Jackson · October 24, 2012, 11:22:56 AM

No question that Engineering 101 is correct.

There are, however, empirical issues involved.

The Oberdorfer pumps work on our engines.

scotty · October 24, 2012, 04:08:51 PM

High School Physics: Yes, size matters. What also matters is size reduction (delta capacity). The more size reduction, the more water is moved out the pump. Look at your pump (inside). It has an aysmetrical shape - the cam. This is why Oberdorfer (sp) has changed the cam to increase the delta. This changed their output from about 3 to about 8 GPM. Another factor is turbulence. Shape and size of ports and blades also will affect the rate of flow. Pump design is really rather elegant. Both pumps seem to work well, I had the Oberdorfer on Paradise and it worked quite well.