water pump impellers

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obsailor

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Jul 8, 2011
49
Catalina 30Mk III Oyster Bay
My Cat 30 gets used for about four months a season in Long Island Sound. At the start of every season i change the impeller of the raw (salt) water Sherwood pump. How about the fresh water Oberdorfer impeller?

Should that be changed as frequently?
 
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Capt jgw

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Feb 8, 2014
1,300
Columbia 36 Muskegon
Aren't those the other way around? My 5411 with fresh water cooling kit has a Sherwood for fresh water, Oberdorfer for raw water. I don't think they would fit the other way around. Anyway, both pumps are running the same hours, I would change them on the same schedule.
 
JK_Boston_Catalina310

JK_Boston_Catalina310

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Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Obsailor,

I believe the C-30 MKIII has the Universal M-25 (not sure on which versions). I have attached the page from the technical manual that covers the coolant pump. This pump is a centrifugal-type pump that uses a metal impeller not a rubber impeller like the raw water pump. This pump doesn't need impeller changes as regular as the rubber impeller.

I checked my coolant pump impeller last year at about 650 hours and it was fine.

The manual does not call for any scheduled changes.

Good luck and fair winds,

Jesse

P.S. I will be passing through Oyster Bay in September or October, any good anchorage suggestions?
 

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C

Capt jgw

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Feb 8, 2014
1,300
Columbia 36 Muskegon
The very first C30s came with a Universal 5411 which had raw water cooling and an Oberdorfer pump. An aftermarket fresh water kit was available that used a Sherwood for the fresh water pump. I'm assuming this is what the OP has.
 
JK_Boston_Catalina310

JK_Boston_Catalina310

.
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Capt jgw said:
The very first C30s came with a Universal 5411 which had raw water cooling and an Oberdorfer pump. An aftermarket fresh water kit was available that used a Sherwood for the fresh water pump. I'm assuming this is what the OP has.
Click to expand
The OP has an MK III. That's the last model version before going to the 309. Build years were the 1990s to mid 2000s. I seriously doubt it came raw water cooled.
 
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Capt jgw

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Feb 8, 2014
1,300
Columbia 36 Muskegon
Ok. Then it's an M25 and has a centrifugal pump like a car engine, the same part as would be on the tractor version of this engine. They can eventually fail, but it takes a long time. If needed, get it from Kubota, not Westerbeke. Kubota's about 1/4 the price for the same part.
 
JK_Boston_Catalina310

JK_Boston_Catalina310

.
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Capt jgw said:
Ok. Then it's an M25 and has a centrifugal pump like a car engine, the same part as would be on the tractor version of this engine. They can eventually fail, but it takes a long time. If needed, get it from Kubota, not Westerbeke. Kubota's about 1/4 the price for the same part.
Click to expand
No, this is not a part I would get from Kubota vs. Westerbeke. On the Kubota pump the metal impeller is stamped steel while the Westerbeke is either bronze with a stainless steel backing plate or all stainless. There are times you can use the tractor equivalent but this is not one I would do on my boat.

Sometimes the "marine grade" is actually different quality.

But like Stu Jackson always says, your boat your choice.

Fair winds,

Jesse
 
woodster

woodster

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Sep 15, 2009
6,243
S2 9.2a Fairhope Al
If no salt water never goes through the circulating pump and only antifreeze it should not matter as the coolant will protect the metal working parts
 
C

Capt jgw

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Feb 8, 2014
1,300
Columbia 36 Muskegon
That's what I was thinking. They'll run 200000 miles in a car that way. Didn't know they did anything different on the pump, all my references show the same part.
 
O

obsailor

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Jul 8, 2011
49
Catalina 30Mk III Oyster Bay
Jessie - there is an anchorage area in the southeast part of the harbor right next to the mooring area with 12 - 15' water. If you have a dinghy can use the dock at the marine center, if you need launch service you have to rent a mooring from the Oyster Bay Marine Center. Nice harbor, no bugs, quiet, town is a 5 minute walk away, a range of restaurants and chandlery at the marine center store. Enjoy it - I do!
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Stu Jackson

Stu Jackson

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Feb 26, 2004
23,102
Catalina 34 224 Maple Bay, BC, Canada
Capt jgw said:
Ok. Then it's an M25 and has a centrifugal pump like a car engine, the same part as would be on the tractor version of this engine. They can eventually fail, but it takes a long time. If needed, get it from Kubota, not Westerbeke. Kubota's about 1/4 the price for the same part.
Click to expand
OK, let's try to clear this up.

There are two pumps on an M25. 1) the freshwater coolant pump, top center of the engine, metal impeller, on the belt, no weep holes; 2) raw water pump, starboard side, not on the belt, run from a cam inside the engine, with weep holes - is EITHER Sherwood or an Oberdorfer.

obsailor said:
My Cat 30 gets used for about four months a season in Long Island Sound. At the start of every season i change the impeller of the raw (salt) water Sherwood pump. How about the fresh water Oberdorfer impeller?

Should that be changed as frequently?
Click to expand
Therefore, the "fresh water Oberdorfer impeller" does not exist.

The upper center pump coolant is on the belt. Lower left is the raw water Oberdorfer.
 

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