Replacement part numbers for the engine coolant circulation pump on the M-25, M-25XP, M-25XPA, M-35, M-35A
The Universal M-25 is built on the Kubota D850 block, the M-25XP and XPA on the Kubota D950 block, and the M-35 and 35A on the Kubota V-1200 block. All those Kubota blocks and the Universal engines use the SAME coolant circulation pump. So the pump for any of those Kubota engine blocks will fit the others. However, you may locate different P/Ns for the same pump because Kubota keys its P/Ns to the specific application in which the engine is used (e.g., B6200, B7200, and 9200 tractors, Bobcats, excavators) and not necessarily keyed to the engines themselves (D850, D950, V1200) So there are oftentimes different Kubota P/Ns for exactly the same physical part (like the coolant pump.)
Additionally, Kubota is constantly updating and assigning new P/Ns, so the current P/N for a coolant pump today could be a different P/N tomorrow. So the pump P/Ns in the Kubota parts manuals on the wiki page Wiki Parts Manuals are the original P/Ns, and they have changed over the years.
Luckily, there is a good source for the current pump P/N - www.messicks.com (an agricultural Kubota dealer that also sells online.) Messicks isn't the least expensive on OEM Kubota parts, but it is a very knowledgeable source, the parts folks are super cooperative and helpful, and Messicks provided many of the Kubota parts manuals that are posted in the wiki.
Kumar Brothers (www.kumarbrosusa.com) sells many (but not all) aftermarket parts for our engines. There are other both OEM and aftermarket Kubota parts sources, such as Country Sales and Service -- so do your homework before buying. OEM Kubota is about 1/3 the cost of a Westerbeke pump, and an aftermarket pump is about 1/2 the cost of Kubota.
The current (7/2019) P/N for the coolant pumps are below.
If you plug any Kubota P/N into the Messicks site:
It will return that P/N history (and any "Replaced by" P/Ns, which you can use to purchase from any source you choose.)
From your local Westerbeke dealer or online:
Westerbeke.com online parts
P/N 300203 (OEM Universal Motors part)
Mounting gasket P/N 300204
From Kubota dealers and aftermarket sellers (e.g., KumarBros) use the Kubota P/Ns:
Old P/N: 15534-73030
Current (7/2019) P/N: 15534-73033
Mounting gasket P/N 15676-73430
When you buy, verify whether the seller includes the mounting gaslet.
Additionally save your old pump, as some sellers do not include the hose nipple (the water heater connection) that screws into the top of the pump.