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Author Topic: Replacement closed coolant water pump for XPB and 35B  (Read 716 times)

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Replacement closed coolant water pump for XPB and 35B
« on: May 11, 2017, 03:21:30 PM »



The Kubota Parts Manual for the M-25XPB is on the TechWiki under "Manuals".  Page 24 shows the closed coolant pump. The M-35BC should fit the same pump as the M-25XPB.

The current Kubota p/n is 16241-73034, available from a Kubota dealer, or online at, or online at Kumar Brothers.
Kumar is not Kubota OEM parts, but they are cheaper and I have NOT heard of Kumar problems.


To clarify, "Kubota manual for the M-25XPB engine" means the manual for the Kubota "cousin engine" of the "Universal XPB," which is a Kubota D-1005.

One "cousin engine" for the M-35B, is the Kubota V1305.
I just now uploaded the manual to the TechWiki site for you. The p/n for that engine is 16251-73032 and 16251-73034.  (They may have different impellers)


A problem sometimes occurs getting parts out of the Kubota manual when it shows two or three different part numbers depending upon the Kubota engine serial number.  The Universal serial number is different than the Kubota serial number.


BTW, on page 18 of the D-1005 manual, you'll see a knock-out on the intake manifold, to the right of the air intake tube.  Kubota p/n 16241-05550 (on page 39 of the V1305 manual,) fits into the knockout hole and you can connect the crankcase breather hose there, instead of zip-tying it alongside the foam "filter" as Wb does.

« Last Edit: May 11, 2017, 03:44:04 PM by KWKloeber »
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Re: Replacement closed coolant water pump for XPB and 35B
« Reply #1 on: May 11, 2017, 03:23:56 PM »

Pretty handy, that Google Translate website! :abd:
1990 hull #1014, San Diego, CA,  Fin Keel,
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Re: Replacement closed coolant water pump for XPB and 35B
« Reply #2 on: December 30, 2018, 08:24:07 PM »

After looking into various options, Iíve ordered a genuine Kubota freshwater pump for my M35B motor. My old pump has been removed, using a procedure designed to minimize the loss of coolant. Iíve confirmed the impeller diameter of 2.25Ē on my old pump. The new pump has not arrived, so has not been installed yet.

Determining the right pump was a little more complex than described in some other threads because of the two incompatible pump designs. This required quite a bit of legwork to nail down, but the results can be helpful to others. Iíll include a lot of details below in hopes of adding clarity to a topic thatís been previously subject to confusion. Knowledge is power, even if itís just auxiliary. ;-)

A brief statement of the issue

Kubota and Westerbeke made a running change during the production of Westerbeke's B-series diesel motors. As a result, two different incompatible pump designs are available, depending on when the motor was manufactured. Furthermore, frequent changes in Kubota's part numbers have resulted in almost a dozen different numbers for the pumps, some of which may be interchangeable and some of which are definitely not.

Page 46 of the B-series Westerbeke parts manual for M25XPB/M35B/M40B motors provides a lot of clarity regarding the two pump models and corresponding impeller sizes:

First, itís important to note that all three of these B-series motors use the same Westerbeke part numbers for the freshwater pump system, so the part numbers (whether you ultimately choose Westerbeke, Kubota, or India/Chinese knockoffs) should be the same for M25XPB/D1005 and M35B/V1305 motors, so long as you know the date code. Someone else's advice for an M35B pump is probably valid for your M25XPB.

Genuine Westerbeke Replacement ($306 as of 2018)

Westerbekeís parts manual shows over 30 various motor parts that changed at a the same point in the B-series production run. The Westerbeke date code is critical. Date codes of ≤E412 (December 2004) use the old parts. Codes of ≥E501 (January 2005) and later use the new parts. These part changes are significant, and include cylinder block and injectors as well as the gear casing, water pump, impeller, and gasket. There's been some speculation here that Westerbeke may have changed the freshwater pump design due to the needs of the marine environment, but the extent of these other changes suggest something more comprehensive was done to Kubota's design. After reviewing Kubotaís marketing literature over the years, it appears to me that Kubota likely made the design changes to address updated emissions requirements. This is (somewhat informed) speculation on my part, so take it with a grain of salt.

The genuine Westerbeke pump for all B-series motors produced though December 2004 (date code ≤E412) is #200820. The gasket also changed on that date, which strongly suggests that the newer pump model will not fit properly on the older motors. This older pump #200820 has a 2.25" impeller.

The newer pump (#201107) used on motors after January 2005 (date code ≥E501) has a 2.75" impeller (70 mm), which would seem to match up with the specs for many of the Asian gray market pumps, in the few cases where they actually disclose the impeller diameter (so buyer beware!).

I called a regional Westerbeke rep, and he verified the proper part numbers (and impeller sizes) corresponding to these date codes. The Westerbeke pump is over $300. My experience with a couple Westerbeke reps is that they generally quote the same prices, so not much money can be saved by calling different ones. Many are also bound to a particular geographical area anyway.

If you are in a remote area and would be burdened by long delays and high shipping charges for making a return of the wrong pump, I recommend paying Westerbeke's premium and buying the pump that corresponds to your date code. There is opportunity to save money by going with a Kubota or gray-market pump, but sorting out all the correct part numbers will make your head spin, and the risk of getting the wrong part may be too great if you're in a remote location. Keep this in mind as you read about the other options.

Genuine Kubota Replacement ($145-190 as of 2018)

Significant money can be saved by purchasing a genuine Kubota freshwater pump, and the dealer prices can vary widely. Ideally you should have the Kubota block serial number when you call, but it can be hard to access:

On my motor Kubota's serial number is on the port side, tucked behind a few coolant hoses which are tightly secured. I stuck my phone camera back there but couldn't get a picture of the whole number, and I was unwilling to disassemble everything to get a picture. My lack of a Kubota serial number made things more difficult, but not impossible.

There are (at least) two different types of Kubota dealers - tractor dealers and engine distributors - and they have access to different types of information that can be more or less helpful. The tractor dealers will generally want the model and serial number of your tractor, which can be limiting for obvious reasons. Even if you already know the Kubota part number, they may be reluctant to sell to you. I spoke to 3 tractor dealers in PA and DE (including Messick's, whom Ken recommended) and got some useful information but not enough to inspire my confidence to buy. Before buying, I wanted them to verify the impeller diameter from their documents or by measuring it themselves. They didn't have access to documentation with impeller information, and couldn't measure it because they either didn't have it in stock or had it "at a different location" (in the case of Messick's). They also didn't seem to have a breakdown showing the impeller part number and/or its diameter. However, one helpful tractor dealer (Burke Equipment in DE) did have a listing that gave the Kubota serial number break between "old" and "new" water pumps. The old pump (currently stocked as #16521-73032, though it seems to change every year or so) is for Kubota motor S/N ≤1U7903, while the new pump (#16521-73034, but recently replaced by 16251-73037) is for Kubota motor S/N ≥1W0001. Presumably "old" pumps have 2.25" impeller, and "new" pumps have 2.75" impeller, though the Burke was unable to confirm this because they don't have that level of detail in their information.

The Kubota date codes are worth some discussion. Kubota's dating guide ( indicates that the changeover from "old" to "new" water pumps occurred on November 2001, which is more than 3 years earlier than Westerbeke's changeover. Is it possible that Westerbeke actually kept over 3 years worth of old motor inventory in their warehouses? Maybe they did a large "last time buy" to give them (and their biggest customers) time to validate the revised motor design? I don't know - it is what it is.

Price quotes for the genuine Kubota pump from the tractor dealers ranged from $142 to $169, not including the gasket, and they had no knowledge of whether their pumps included the return pipe (which some here have complained was missing from their replacement pumps).

Messick's suggested that due to the nature of my questions it would be better to talk to a Kubota engine distributor, and they gave me contact information for Engine Distributors Inc in Blackwood, NJ ( The parts guy there was very helpful and persistent at looking things up. I could hear him leafing through a bunch of parts manuals for different serial numbers (since I did not have my own serial number). He told me that he could not find any reference to #16251-73032 that I was requesting (I guess it's because he was using printed manuals that may have been over a year old). But based on my info that my engine is the older version with 2.25" impeller, he pulled up 16241-73034 (which he had in stock) and 16241-73030 (previous number for the same thing). I recognized both numbers from other research I had done online. He said it definitely had a 2.25" impeller (based on the impeller number in the parts breakdown), and that the return pipe is included because it's pressed in (I think it's threaded in, but as long as it's included I don't care). Based on his helpfulness and patience I had decided to buy from him right away no matter what the price. I was relieved when he quoted $123.59 for his in-stock 16241-73034 pump, the best price I had seen for this anywhere. Gasket and shipping brought the total up to $144.66 all-in cost.

Note that Kubota seems to change part number frequently, resulting in a terribly confusing proliferation of part numbers. Here is my best attempt to summarize the various numbers:

"Old" pumps with 2.25" impeller: 16241-73030, 16241-73032, 16241-73033, 16241-73034, 16241-73037, 16251-73030, 16251-73032 (current model, but seems to change frequently).

"New" pumps with 2.75" impeller: 16251-73034, 16251-73037 (very recent change not shown on most dealers' lists)

WARNING: This is my best attempt based on information available to me. Do not rely on my listing alone - always ask to verify impeller diameter before ordering, and post corrections and updates to my list on this thread.

Gray Market Knockoffs ($46-99)

The low-end option for sourcing these pumps are the Indian and Chinese suppliers found on ebay and Amazon for prices as low as $46. I suggest you be very careful to make sure you get the right impeller size. Many of the listings that I saw did not list impeller size, or specified it as 70 mm with no mention of a 57mm/2.25" version that the vast majority of us need for boats made before 2005. I am also concerned that some of these Asian pumps seem to cross-reference multiple Kubota part numbers that correspond to both the "old" pumps and the "new" pumps. Which one is it? It can't be both! One ebay seller even listed a 16251-73032 knockoff which should have a 57 mm impeller, but the photo showed a 70" tape measure across the impeller. Wrong picture? Wrong part number? There's no way to know without asking - buyer beware!

Kumar Brothers, which seems very popular and slightly more expensive than some others, doesn't give diameters in their listing, but at least their listings seem to be clear about which Kubota part number they correspond to. I called Kumar on the phone and the guy was very eager to assist and provide information. He said he didn't know the impeller diameters, but that the person who does know would be in the next day and call me back. They left a phone message the next day that they had the 2.25" model, but by that point I had already ordered the genuine Kubota pump (which I suspect Kubota may outsource to one of these same manufacturers). Kumar's price is $78-99 (including gasket, return pipe, and free shipping), depending on where you find it.

If I had not gotten so much help from EDI, I would have given Kumar Brothers a try.

The pump that I purchased has not arrived yet. Once it comes in I will verify that it includes the return pipe and other claimed specs, and post a correction if needed. I'll also post my pump removal (and eventually, install) procedure on another thread.

2001 MkII Breakin' Away, #1535, TR/WK, M35BC, Mantus 35# (at Rock Hall Landing Marina)

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Re: Replacement closed coolant water pump for XPB and 35B
« Reply #3 on: January 04, 2019, 08:03:36 PM »

The pump came the other day. I confirmed that it is 2.25" impeller.

FWIW, the pump was OEMed by TBK (Tokyo Seiko division), and was labeled "Made in Japan". The previous pump that I removed was OEMed by Aisin. Both are major Japanese automotive parts suppliers, and both claim to be the biggest water pump manufacturers in the world (go figure). Any prior speculation that Indian/Chinese gray-market pumps are supplying to Kubota appear to be untrue.

There might be an opportunity to cut out another middle man by buying directly from TBK instead of Kubota, but it's also possible that this is a custom (captive) design specifically for Kubota.

I posted a few other installation details over at,8939.msg77420.html#msg77420.
« Last Edit: January 04, 2019, 10:32:30 PM by Breakin Away »

2001 MkII Breakin' Away, #1535, TR/WK, M35BC, Mantus 35# (at Rock Hall Landing Marina)
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