Raw Water Pumps

[Ron Hill]

There has been some traffic about the merits of certain water pumps over other brands.  I want to point out to everyone that eventually all water pumps will leak.

The seals tend to wear out and/or the shaft gets a wear pattern.  Either of these conditions or both will cause a leak.  I believe that the Oberdoffer is a good pump as is the Sherwood pump.  
One of the big advantages of the Oberdoffer is that parts can be purchased at discount vrs. the Sherwood that controls part prices like Yanmar.

All raw water pump have "weep holes" to let you know that it could be leaking.  All RW pumps have two internal seals.  One seal keeps the water in the pump and the other seal keeps the oil in the engine (with the weep holes in between).

There are advantages and disadvantages to each of these two pumps.  (I might mention that there was also a third pump by the Johnson Co that was put on some of the early M25 engines). Some Sherwood, but mostly the Oberdoffer pumps were on the M25XP engines with the 3 " HX.

The Oberdoffer pump has all non corrosive metal parts and is easier to service (impeller/shaft change) on the engine, but must be removed to change seals.  
The Sherwood has a corrosive center section and must be removed to have the seals changed, but is easier to change seals, once removed.  The impeller can be changed on the engine, but the bolt heads are on the engine side ?!?

There has been some posts about changing the Sherwood pump out for an Oberdoffer.  I saw Joe Joyce (Westerbeke Service Manager) at the Annapolis boat show and mentioned this topic to him.  We agreed that the Oberdoffer could be modified to fit, but he said the Oberdoffer pumped 50% less water !!
If you look at both pumps it's obvious that the pump cavity of the Sherwood is larger and its impeller has almost twice as many blades.  

The bottom line is that I'd be cautious before changing out pumps.  
The higher engine temperature (less raw cooling water) may not show up immediately while the hoses/HX are clean, but I'm sure that the increased temperature will eventually show up.  

A few thoughts before changing pumps on your M35BC & M25XPB engines.  

[cmainprize]

Wow, 50% less water.  That number should kill all thoughts of changing the pump.  Thanks for doing the research. 

[Stu Jackson]

Not really.  Unless maybe you're sailing in boiling water with an old 2 inch HX.  Our Oberdorfers, with an S, have been keeping our M25 going just fine for 13 years.  Water flow?  Not an issue.  I'd rather be able to get to my impellers without having to jacka** around with nuts/screwheads that are the back side of the pump.

Different engines, different pumps, different boats and skippers.  Your boat, your choice.

[prh77]

I have an Oberdorfer on my 25 XP with a 3 inch HX and have no problems. I feel it is a much better design than the Sherwood. Folks with the MK ll boats and larger engines may want to due a little research, as the lower flow rate maybe an issue,especially in warmer climates and installations where HX maintenance is neglected

[Tom Glennon]

I switched from Sherwood to Oberdorfer on my '87 M25XP this past season, and was very pleased with the performance... great flow out the exhaust... and temp kept at a steady 160 degrees after normal warm-up.

[Ken Juul]

So far everybody that has switched to the Oberdorfer has operated their boat in cold water (San Fran, NY, Mass)  anybody down south use one?  

[waterdog]

I have an Oberdorfter with 3 inch HX.   Used extensively in warm water (mid 80s and higher).   My engine temp stays consistently at 160 on my gage in both temperate and warm waters from 54 to 89 degree sea temp.   Only a serious blockage on the intake will give me a temperature rise. 

[lazybone]

My Gal came new from the factory with a Sherwood.  After two 90 mile trips by the Catalina dealer to make warrenty repairs to the pump they changed it over to an Oberdoffer (sp).
No problems for twelve years.

We replaced it with another obee after 12 yrs because it began to leak.