The engine is a Westerbeke 40-108, built in 1980, s/n ED 22432U 559349F. Cylinder head number 37116500/3.

Rebuilt the engine March 2006. Had the cylinder head, exhaust manifold, injector pump, injectors, transmission, heat exchanger, and oil heat exchanger rebuilt.

The drain plug on the oil sump is a 1/2"-14 BSPP thread plus a 13/16" washer (copper or phenolic)

Engine water discharge hose 5/8" ID.

Engine develops 37HP @ 3,000 RPM. Cruising RPM ~2,000. According to Westerbeke, with a 2:1 transmission, the ideal prop size is 18x10 (2 blade) or 18x8 (3 blade). For each 1" reduction in diameter, increase the pitch by 2".

The engine holds 5 quarts of oil. I've using Castrol Syntec 5W-50 (rated CF). The engine burns quart/25 hours at about 1,650 RPM. Changed to this heavier weight oil to minimize engine oil leaks.

In 2001, changed all the hoses, the heat exchanger, and the oil cooler.

I created a cross-reference list between Westerbeke W40 and Perkins 4.108 parts. I've found that the Perkins parts are anywhere from two to 10 times less expensive than the equivalent Westerbeke parts. The cross-reference list is here.

In 2009, added a remote oil filter system to make oil filter changes easier and less messy.

Item Manufacturer Model No.
Oil Filter (3/4-16 thread, O-ring OD 2.834", ID 2.462", height 5.189", OD 3.663"). No height restrictions with remote oil filter mount. NAPA

Fleetguard (Cummins)
1806 (no grip or flats)
51806 (no grip or flats)
PH2821A (was PH43)
Thread too small!

BT216 (too tall 5.4")
P554403 (too tall 5.4")
LF701 (too tall 5.75")
Oil drain plug washer   13/16" (M20 would also work in a pinch)
Racor Racor 500FGSS (60 gph) (pre 1998)
Racor Fuel Filter (Primary) Racor 2010SMOR (2 micron)
(uses spacer adapter 15424)
Secondary Filter spin-on adapter ABC Precision Machining DP-1000
Secondary Fuel Filter

(Italics are non- spin-on filters)

3361 (w/o drain)
33361 (w/o drain)
FS1235 (w/ drain)
3192 (w/ drain)
Sherwood Water Pump
(flow of 0.0068 gallons/rev, 10 GPM @ 1,500 RPM)
(New in 2002)
(F85 obsolete? Replace with G65 [2011])
F85 (G65 replacement?)

Sherwood Water Parts:



Mounting gasket


Sherwood Water Pump Kit (impeller & gasket) Westerbeke 33104
Sherwood Water Pump Cover Replacement Speedseal Nitrile 70 O-ring
65mm ID x 1.5mm
Screw threads " UNC
Heat Exchanger Zinc
(1/4" plug, 3/8" zinc diameter, 1 3/4" long)
Banjo Washers for secondary fuel filter Westerbeke 11944 (top of filter, M10)
12522 (sides of filter)
Banjo washers sizes ID x OD x Thickness 5/16" x 7/16" x 0.038"
13/32" x 1/2" x 0.051"
13/32" x 9/16" x 0.050"
17/32" x 11/16" x 0.064"
Radiator cap - exhaust manifold AC Delco

RC15, 15 lbs., stainless
10229, 13 lbs.
10230, 16 lbs.

24306, 14 lbs.
Radiator cap - expansion tank AC Delco
RC2, 4 lbs., stainless
"A8", 10228, 7 lbs.
11499, 7 lbs.
Thermostat Westerbeke 24688 160F
Injector Pump (rebuilt 3/06) CAV DPA 3249F020 DSA
Ser R17915WW  Mod --
PH25E500/6 3190
Injectors (rebuilt 3/06) CAV BKB40 SD5224 ZW
DES No 5352102
Westerbeke 11701
Oil Cooler (serviced 2/06)   31 tubes
Heat Exchanger (serviced 2/06)   78 tubes
Seawater intake hose Shieldsflex Series 250 " wire-reinforced
Hot water heater hose   5/8" heater hose, 13 ft.
Expansion tank hose   5/8" heater hose, 2 ft.
Heater hose (on engine)   5/8" heater hose
Exhaust hose (replaced 2005) Trident Marine Shieldsflex Series 250 1 7/8" ID wire-reinforced,  4 ft.
Motor mounts (new 1/06) Bushings Inc. DF-100
Start motor (replaced 6/01) Delco-Remy
1109377 9M 19
(has 4 mm and 10 mm studs!)
Diesel Fuel Hose (1984) Aeroquip FC234-05 (" ID, 0.58" OD, 1500 psi max operating pressure)
Hydro-Hush muffler (new 2006) Custom built by Joe at Consolidated Uses a 1/2"-18 x 1/2" (or 3/4") plug
Serpentine belt
13/16"x42-1/8" OC or 20mmx1069mm OC, angle 40, 6 ribs
Micro-V 25-060415
Fuel shut-off cable Teleflex CC34310 (10 ft.)
replaced 2012
Engine Paint Color Duplicolor DE1607
(can't swear to this)


Service Schedule

Hours Description
100 Change engine oil and filter
Check zinc
Check transmission fluid
200 Change primary and secondary fuel filters
Change transmission fluid
500 Torque cylinder head bolts
Adjust valve clearances
800 Remove and check fuel injectors
Check compression

Rule of thumb: Rebuild the engine when the oil consumption (not leakage) exceeds one quart per eight hours per 100 horsepower.  So, with the 40 HP engine, when the fuel consumption exceeds one quart every 20 hours, then rebuild.

Placed all the engine wires inside flame-retardant split-convoluted (split loom) polyethylene sleeving. The two sizes used were 3/8" and 1/2".

Replacing exhaust hose

Heat the end of the hose with a heat gun being careful not to burn the rubber. Once warm, take a 2" wooden bung (e.g., an emergency seacock plug), put it in the heated end and start hammering it until the top of the bung is 2" below the end of the hose. Turn the hose over and use a broom handle to bang out the bung. Do the same thing with the other end of the hose.

To install the hose, feed one end of the hose down between the engine and engine bed on the port side just forward of the oil filter. Feed the other end of the hose over the exhaust manifold fitting while putting a bend in the hose near the exhaust manifold. Bending it is the secret to getting it straight on to the fitting. I used a hi-temp RTV (silicone) gasket maker to cover the fitting before slipping on the hose. Once hose is all the way on the fitting, put on two hose clamps to hold it in place.

Remove the four screws that hold down the Hydro-Hush muffler. Align the hose with the Hydro-Hush and put the hose on the hitting (make sure to first put RTV on the fitting). Then, adjust hose angle to get the Hydro-Hush back to its mounting position and screw it down. Put two hose clamps on this end of the hose.

To create enough room to maneuver the hose between the engine bed and the engine I carved away about 3/8" of material on the top edge. There's a 1/4" stainless steel plate inside the fiberglass that I cut away.

Random Temperature Readings (F)

Location F
Exhaust water 80
Expansion tank 170
Alternator case (light duty) 104
Thermostat hose 180
Stuffing box 79
Exhaust elbow 216

Conditions: May 8, 2011, seawater 68F, air 74F, 1,600 RPM, in gear, tied to dock.

Fuel Tank

The new tank (2006):

Capacity: 50 gallons
Usable: 49 gallons at up to a 20 heel
Weight: 52 lbs. (empty)
0.125" 5052 Aluminum with 0.188" side plates

Deck fill: 2" Sea-dog 351331. Uses an O-ring under the cap (2.0" OD x 1/8" thick, neoprene)
Fuel lines are 1/4" ID with compression fittings

Fuel tank vent: 5/8" hose to a Perko (0509DP4CHR) tank vent fitting (replaced 2016)

Tank designed by me, built by Carter Fabrications in Millersville MD.

Dipstick Measurements for Tank Capacity
Inches from Bottom Gallons   Inches from Bottom Gallons
4.75" 2   16.50" 30
6.50" 5   18.38" 35
8.63" 10   20.38" 40
10.50" 15   22.25" 45
12.50" 20   24.13" 50
14.50" 25      

Draining all the liquid out of the tank via a siphon, the remaining liquid measured 0.75" from the tank bottom, which I'm guessing is about a quart. The calibration was done pouring one gallon at a time into the tank.


Zinc Canada Metals (Canad) CMC-3
Shaft 1" diameter, 21 3/8" long, stainless steel (replaced 1/2001)
Cutless 1" ID, 1" OD (turned down to 1.40" and knurled) , 4" long. (Morse Marine Bearing, Bonito, E00800, replaced 5/2005) Two set screws 180 apart at approximately 10:00 and 4:00. Set screws -- 1/4"-20 x 3/8" (2)
Propeller 15"D x 11"P RH 3-blade MP. New, 4/2000. Michigan Prop (stamped 07/99) (reconditioned 5/2009).
Aperture 16" H
Key " x " x 1 9/16" brass

The cutless bearing sits inside the fiberglass stern tube. Two screws (10:00 and 4:00) are set in the stern tube with stainless threaded inserts. Set screws are used. The screws have putty over the tops of them. The bearing is turned down from 1.5" to 1.40" and then knurled. There are dimples where the set screws go.

I replaced the 3-blade 14"D x 11"P (reconditioned 3/1998 Buedel's #25226, Manufactured 3/1980) prop with a 15"D x 11"P Michigan Prop 3-blade. I also had the yard fair the water entry into the prop by removing the "shoulders" on the deadwood in front of the prop. The reason for this was to get rid of the cavitation and to put more power into the water to fight choppy seas.

The small nut goes against the prop and the large nut behind it.

Stuffing Box

Hose 3" long by 1" ID. Material is exhaust hose 0.405" thick (5 ply?). Black with a blue stripe (Buck-Algonquin No. BUC H0175) (new hose 1/2001)
Packing Gland 1"ID, 1.85" OD Wilcox Crittenden WIC8657-100 (1/2001 no longer made by WC)
Packing 4-rings. Inner and outer rings are 3/16" TefPack. The center two rings are Drip-Less Moldable Packing formed into approximately 3/16" rings. Both packings are from Seafit (aka West Marine) but actually made by Western Pacific Trading. (repacked 1/2001)
Body Thread Length 1.3"
Jam Nut 1.9" OD

The easiest way to install the packing:

  1. Wrap three turns of TefPack packing around a 1" diameter cylinder. Cut two circles with a diagonal cut from the packing.
  2. Take the green Drip-Less Moldable Packing and warm it in your hands. Then, roll it between your fingers into a long "log" that's the same thickness as the TefPack packing.
  3. Make two logs of the Drip-Less Moldable Packing, with each being the same length as the TefPack packing.
  4. Remove the old packing from the hex spud nut.
  5. Insert the first TefPack circle into the nut, carefully noting where the split is in the circle. Puch it down into the nut either with a pushing tool or gently tighten the spud nut on the packing gland until the gland touches the TefPack packing material and then back off the hex spud nut.
  6. Insert the two circles of the Driip-Less Moldable Packing, taking care to make sure that the splits in the circle do not line up with each other. Again, push it down all the way into the hex spud nut, as above.
  7. Insert the last TefPack packing circle into the hex spud nut.
  8. Hand-tighten the hex spud nut on to the packing gland.


Changed from using a takeoff on the alternator to using the mechanical take-off on engine (above dip stick). This was done because of interference problems between the electronic tachometer and the Link 2000-R voltage regulator.

Teleflex 82430P electronic tachometer, including hour meter (installed 11/98).
Teleflex 1A96042 sending unit (voltage out)
Teleflex 52776P 0.104" square drive tang

The tachometer has an error with its readings:    True RPM = 84 + 0.858 * Tach reading (4/2000). I determined this with a photo-tach. I corrected the tach calibration by setting different switch settings on the tach (ratio of wrong reading over true reading -- 4/2000).

I also had made up a 6" long mechanical drive cable (1998) because of the sending unit was too wide to screw onto the engine. The cable was made at a speedometer shop. On the engine side, the cable has a female 7/8"-18 thread. On the sending unit side, the cable has a male 7/8"-18 thread. Replaced the cable in 2006.

The previous hour meter had 1258 hours on it. (11/98)

Other gauges are Stewart Warner


Hurth HBW100-2R, Nr: 09-08324, manufactured in 1979, rebuilt 1/06


Gear ratios: Fwd 1.790, Rev 1.860

Holds 12 oz. of ATF fluid.

There is 1.75" clearance between the end of the flange and the compression nut on the stuffing box.

Hurth bought by ZF Industries in 1995.

Damper plate had a number on it: 1866 061001