Westerbeke marinizes Mitsubishi industrial blocks

I've mapped Westerbeke W-series and B-series diesels to a Mitsubishi base engine. Two engines use Perkins. Order internals as industrial spares.

Westerbeke uses a Mitsubishi base engine (mostly)

Westerbeke small and mid diesels use a Mitsubishi base engine. That set includes the W-series and the B-series (12B-Two, 30B-Three, 42B-Four, and similar).

Those engines mainly use Mitsubishi L-series and K-series blocks. Internal service parts cross to Mitsubishi numbers through industrial channels.

Two engines use Perkins.

Westerbeke to base-engine map

Westerbeke model	Base engine	Cyl
W10-Two	Mitsubishi K2AS	2
W13	Mitsubishi K2C	2
W18	Mitsubishi K3A	3
W21	Mitsubishi K3D	3
W27	Mitsubishi K4D	4
W33	Mitsubishi K4F	4
12B-Two / 20B-Two	Mitsubishi L2E	2
30B-Three	Mitsubishi L3E	3
35B-Three	Mitsubishi K3F	3
38B-Four	Mitsubishi K4D	4
42B-Four	Mitsubishi K4F	4

The exceptions: W40A and W52 are Perkins

W40A to Perkins 4-107. Westerbeke marinizes a Perkins 4-107 wet-liner block. Internals cross to Perkins 4.107 numbers.
W52 to Perkins 4-135. Westerbeke marinizes a Perkins 4-135 block (Toyo Kogyo / Mazda R2 casting). Internals cross to Perkins 4.135 numbers.

Two hops out, W52 also crosses to the Mazda R2 (as used in the Mazda B2200 and Ford Ranger).

If you have a W40A or W52, look these up as Perkins engines.

B-series rows here use Mitsubishi L-series and K-series. Read the base engine line on its page. If you order, confirm with a Mitsubishi dealer first. See Methodology.

I've inferred a few Mitsubishi K and L codes from displacement. Dealers document those codes widely.

Find parts for your Westerbeke

Open your model in the table above.
Open the Industrial / tractor part equivalents view.
For consumables, use the charts below.

See the impeller chart.

See the oil filter chart.

See the fuel filter chart.

Marine hardware you still buy as Westerbeke

The Westerbeke seawater kit, panels, and many heat-exchanger anodes stay Westerbeke or aftermarket anode makers.

W40A is Perkins 4-107. W52 is Perkins 4-135 (Toyo Kogyo / Mazda R2 casting).

B-series rows here use Mitsubishi. Check the engine page.

How to confirm the block

Westerbeke model names (12B-Two, 30B-Three) encode cylinders. Use the table for the industrial code.
K-series versus L-series uses a different industrial parts book.
Pencil zincs such as Westerbeke 11885 cross to Sierra 23-6400 / Tecnoseal TEC-E0 on the Universal side of the same pencil. That pair is anode interchange.

See anodes.

FAQ

Are B-series engines Kubota?

Several B-series rows are Mitsubishi L2E, L3E, K3F, K4D, or K4F. If a page is blank, I haven't sourced a base engine.

W50?

The W50 here uses a BMC/Leyland 1.8 block. See the engine page.

These numbers come from public and third-party sources. They can be wrong. Check against an official source before you order. Methodology · All guides.