As generally deduced, Westerbeke only marinizes short blocks from real manufacturerd. I have had three.
They actually start with a fairly complete engine right down to the starter and alternators on some. They make the bell housings and add a raw water pump, manifold, mounts HX, wiring harness and a few other marine specific items, oh and paint them red, as opposed to black... .
The base engines are strong and reliable, but the parts that Westerbeke adds are where problems will lie: alternators and regulators, water pumps, and especially electrical components.
No engine manufacturer makes their own starters, alternators, fuel lift pumps etc. etc.. They are all pretty much the same. Yanmar uses Hitachi alts & starters, Westerbeke uses Mitsubishi, Balmar or Leece-Neville. I have not found a single brand to have any more or less reliable alternators, starters, fuel lift pumps etc.. They also use pump companies like Johnson, Jabsco etc. to make the OEM pumps. Some Yanmar's share the same pump parts with some Westerbeke engines because the pumps are built by the same OEM supplier...
Their wiring is poor grade, as though they didn't know these in engines were being used in boats ON WATER.
There is not an engine maker I know of that makes a decent wiring harness, just a sad reality.. Yanmar IMHO, as a marine electrician, is one of the worst when it comes to wiring harnesses.
Connectors are the same poor grade.
They all pretty much use crappy on-engine wiring.
And while Kubota parts are widely available, they're little if any cheaper.
Westerbeke engines are marinized Mitsubishi industrial engines not Kubota's. Universal, Westerbeke's sister company, marinizes Kubota's.
Kubota parts are a LOT, LOT, LOT less expensive than through Westerbeke. I have saved over 80% on many Kubota items. IIRC I have paid about $7.00 for a Kubota glow plug and Universal wanted about $80.00.....
Even Mitsubishi parts are a LOT, LOT, LOT less than through Westerbeke but finding the Mitsubishi parts can be tedious as their "contract" with Westerbeke disallows for Mitsubishi dealers to sell parts to Westerbeke customers, if they know they are going on a Westerbekje engine..
What you are most likely to replace are the parts Westerbeke uses to marinize. Get the credit card ready.
I work on all the engines and I don't find Westerbeke / Universal to be out of line parts price wise for the "marine" market.. Volvo is the worst but they all GOUGE for the "marine" label.
BTW if you get creative Yanmar parts can also be purchased through industrial/farm channels too. These engines are also widely used in industrial and farm applications. There are a LOT of John Deer / Yanmar powered tractors out there and even through a John Deer dealer (not known for inexpensive parts) the base engine parts can be had for quite a bit less...