Perkins · Inboard diesel

Perkins 4.108

The Perkins 4.108 is a four-cylinder, indirect-injection diesel of 1760 cc from Perkins Engines in Peterborough, England; marinised at the factory as the 4.108M, it became one of the most common auxiliary engines in older sailing yachts and motor sailers. Over the years Perkins built it with three cooling layouts and changed the filters, glow plugs, lift pump and exhaust elbow, so early and late engines often take different parts. The smaller 4.107 shares the Jabsco sea-water pump and the front crankshaft seal but not the internal parts, so it is on this page too, and the notes say where a part is confirmed for both. Perkins no longer builds the engine but still sells several hundred genuine parts for it (engine numbers starting with ED); many US boats have a 4.108 marinised by others such as Westerbeke, whose cooling parts are not covered here.

Manuals & documents
Wear parts & part numbers
Service intervals
Specifications
Good to know
Videos & how-tos
Fitted in
On the marketplace

Manuals & documents

Perkins no longer offers the 4.108 manuals as downloads: paper copies of the workshop manual can be ordered from a Perkins distributor, and once you register your engine, My Engine shows parts books and service literature. The other links go to Perkins’ parts pages, an archived Perkins engine-number guide and Jabsco’s documents for the sea-water pump. We host no manuals.

Perkins 4.108 Series page: genuine parts, common service items, engine registration Manual portal shop.perkins.com · EN
Perkins service literature: paper workshop and maintenance manuals for every Perkins engine through distributors, literature for older engines in My Engine Manual portal perkins.com · EN
Perkins distributor locator: order the printed 4.108 workshop manual and genuine parts locally Printed manual (to order) distributorlocator.perkins.com · EN
Perkins My Engine: register your engine for parts books, manuals and service literature Manual portal myengine.perkins.com · EN
Perkins guide: where the engine number plate sits (position A on the 4.108) and how the number is built Servicing guide shop.perkins.com · EN
Perkins engine number guide PP827: family code ED = 4.108, year and country codes (archived 2011) Archived maker page web.archive.org · PDF · EN
Jabsco 3270-0001 engine cooling pump for the Perkins 4-107/4-108: instructions and parts list Parts catalogue xylem.com · PDF · EN
Jabsco (Xylem) flange-mount impeller pumps: model table with 3270-0001 and 3270-200 (40 l/min at 1500 rpm) Spec sheet xylem.com · PDF · EN
Jabsco impeller cross-reference table (1210-0001 = Perkins 0460038) Parts catalogue xylem.com · PDF · EN

Wear parts & part numbers

Part	OEM number	Also fits	Note
Raw water pump impeller	`0460038`^3,2,1,4,5	Jabsco `1210-0001`^1,2	For the Jabsco 3270 sea-water pump of UK factory-marinised engines, also on the 4.107. 12 neoprene blades on a splined brass hub, 57 mm diameter × 31.5 mm wide, 16 mm shaft. Not for the Sherwood pump on some US-marinised engines.
Pump cover gasket	`0490785`^7,6,1	Jabsco `3298-0000`^1,6	Paper gasket under the six-screw end cover of the Jabsco 3270 pump (4.107 and 4.108), 76 mm outside diameter.
Impeller kit (with gasket)	`90033-0001`¹	—	Jabsco service kit for the 3270 pump (Jabsco number, no Perkins number): impeller 1210-0001, cover gasket 3298-0000 and shaft seal 92700-0060.
Raw water pump	`3270-0001`^1,8	—	Jabsco number, 3/4 in NPT ports; Jabsco lists it for the Perkins 4-107 and 4-108. No Perkins number confirmed. Not a direct replacement for the Sherwood pump on some US-marinised engines.
Raw water pump	`3270-200`^9,10	—	UK version with 3/4 in BSP ports, the pump dealers supply for UK factory-marinised 4.108s. When you change it, leave the adaptor plate in place (see tips).
Raw water pump	`35615`^11,12	—	Perkins’ own number for the gear-driven sea-water pump; Perkins lists it only for the 4.108 (engine numbers ED…). Perkins does not say which Jabsco version it matches, so compare the ports (NPT or BSP) with your old pump.
Adaptor plate	`33154119`¹	—	Perkins number of the adaptor plate on the timing case that carries the Jabsco pump (4.107 and 4.108), as given in Jabsco’s instructions. If it has been loosened, it must be re-centred with the Perkins alignment tool (see tips).
Water pump gaskets	`36821506`^13,14,15,16replaces 36821503	—	Gasket between the Jabsco pump mounting and the engine; a dealer lists it for the 4.107 and 4.108 and gives 36821503 as the old number. Dealers also sell the three gaskets of the pump mounting as a set.
Engine oil filter	`2654403`^17,18,19	—	Spin-on filter of later engines: 96 mm diameter, 131 mm high, thread 3/4-16 UNF. Also fits the 4.236, 4.165 and other Perkins engines.
Engine oil filter	`26540154`^20,21,22	—	Paper element for the reusable steel bowl of early engines, 93 mm diameter × 98 mm. A conversion head for the spin-on filter 2654403 exists.
Fuel filter (engine)	`4326658`^24,25replaces 26561117	Delphi `HDF296`²³	Element for the CAV/Delphi-type filter head of later engines, 88 mm diameter × 70 mm, with sealing rings. Two dealer sources, no Perkins document.
Fuel filter (engine)	`30242`^26,27	—	Paper element for the bowl-type filter housing of early engines, 71 mm diameter × 84 mm (also listed for the 3.152 and 4.203).
Fuel filter (engine)	`2656614`^28,29	—	Perkins ‘Eco’ element without a canister, listed by Perkins for the 4.108 (engine numbers ED…) and 4.236. Which of these three elements fits depends on the filter head on your engine, so compare with the old one before ordering.
Fuel lift pump	`ULPK0011`^30,31,32,33	—	For early engines with a two-bolt mounting flange; a dealer lists it for the 4.108.
Fuel lift pump	`ULPK0014`^30,34,35,33	—	For later engines with a four-bolt mounting flange; two dealers list it for the 4.108 (one also for the 4.107).
Thermostat	`2485608`^36,37	—	Listed by Perkins for the 4.108 and 4.236; Perkins also lists 2485646 and 2485666 for some 4.108 builds. Marine engines take the 75 °C version, automotive and industrial ones 82 °C, so check the stamp on the old thermostat. Fit a new housing gasket.
Coolant pump	`U5MW0054`^38,39,37	—	Genuine pump kit with press-fit pulley. Dealers also sell the genuine pump U5MW0100 for the 4.108, with a circlip groove on the shaft, so check how the old pulley is held.
Heat exchanger	`2486H005`⁴⁰	—	Bowman number of the combined exhaust manifold and heat exchanger of later factory-marinised engines, supplied with tube stack, end caps and two gaskets to the cylinder head. One dealer source.
Heat exchanger gasket	`24865061` · `24865062`^30,41,42	—	The two gaskets of the Serck heat exchanger; a dealer sells them with O-ring 2415836 as the heat-exchanger seal kit for the 4.99, 4.107 and 4.108. Perkins’ own catalogue lists them for the 4.236, and the 4.108 had several cooling layouts, so compare with your old seals first.
Heat exchanger end-cap O-ring	`2415836`^30,43	—	O-ring of the Serck heat exchanger, part of the same dealer seal kit (see the gaskets above).
Exhaust mixing elbow	`41316509`^44,45,13	—	Genuine exhaust outlet elbow on the exhaust manifold; Perkins lists it for the 4.108 (engine numbers ED…) without naming the flange or water connection, so compare with your old elbow. Stainless steel replacements are sold (see tips).
Exhaust manifold gasket	`36862232`^46,47,13	—	Gasket between cylinder head and exhaust manifold; a dealer lists it as the equivalent for all 4.108 versions and sells them in pairs.
Alternator V-belt	`2614B632`^48,49,50	—	About 1080 mm long. Perkins lists about a dozen belts for the 4.108, depending on alternator and pulleys; early marine engines run 7/16 in (12 mm) belts, later factory-marinised ones 1/2 in (13 mm). Compare length and width with the old belt.
Glow plug	`2666409`^51,52,53	—	For later cylinder heads with the glow plugs screwed into the head; Perkins also lists 2666408 for the 4.108. Early engines have a Thermostart heater in the inlet manifold instead.
Injector nozzle	`2646724`⁵⁴	—	Four per engine; nozzle for the 4.108 and 4.165. The nozzle is the part that wears: injectors are usually reconditioned with new nozzles and new copper sealing washers.
Pressure switch	`2848062`^55,56,57	—	Oil pressure switch for the warning light or alarm, not a gauge sender: single spade terminal, tapered thread, earths through the engine block, so check your wiring if the block is isolated.
Drain plug	`0650593`^58,59,60	—	Sump drain plug for the common sumps with a 3/4 in parallel thread; some sumps take a taper-thread plug instead. Use a new copper washer.
Front crankshaft seal	`0730098`^61,62,37	—	Front crankshaft oil seal; Perkins lists it for the 4.99, 4.107 and 4.108.
Rear crankshaft seal	`36883115`^63,13,64,65	—	Genuine rear crankshaft seal; Perkins lists it for the 4.108 (ED) and a dealer as the 4.108 rear seal. The original design is a rope-type strip in two half housings behind the flywheel, which often leaks on inclined installations (see tips).
Gasket set	`U5LT0304`⁶⁶	—	Top (cylinder head) gasket set for the 4.108 and 4.108M; Foley Engines, a Perkins dealer, lists its set as replacing Perkins 85786 and U5LT0304. One dealer source.
Gasket set	`U5LB0013`⁶⁷	—	Bottom gasket set for the marine 4.108M (engine numbers ED…), as listed by Foley Engines, a Perkins dealer. One dealer source.

Numbers checked against the sources below on 23 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

Task	Interval
First service	After the first 25–50 h on a new or factory-replacement engine: oil and filter, check the cylinder-head nut torque and reset the valve clearances (0.30 mm cold), check for leaks, belt tension and engine-mount bolts. Running in at light load is not needed⁶⁵
Oil level check	Daily or every 8 h, whichever comes first: engine oil, gearbox oil, coolant in the header tank and oil pressure (Perkins); dealer guideline: before every start^65,68
Engine oil change	Every 100 h or 2 months, whichever comes first (Perkins). Dealer guideline for boats: every 50 h, or at the start and in the middle of each season^65,68
Oil filter	With every oil change: renew the paper element or the spin-on canister⁶⁵
Fuel filter	Final fuel filter element every 400 h or 12 months; clean the water trap every 100 h or 2 months (Perkins). Dealer guideline for boats: change the filters with every oil change^65,68
Air filter	Wash the gauze of the air intake every 100 h or 2 months (maintenance schedule; the manual’s air-filter section allows 150 h), more often in dusty conditions⁶⁵
V-belt check	Check the tension every 100 h or 2 months; monthly on engines rated above 3000 rpm⁶⁵
Valve clearance	Every 400 h or 12 months: 0.30 mm (0.012 in), inlet and exhaust, engine cold⁶⁵
Injectors	Have the injectors serviced every 400 h or 12 months⁶⁵
Gearbox oil change	Change every 400 h or 12 months; check the level daily⁶⁵
Hoses & clamps	Check hoses and clips every 400 h or 12 months; check the engine for oil and water leaks every 100 h or 2 months⁶⁵
Drain fuel tank	Drain and clean the fuel tank every 400 h or 12 months⁶⁵
Sea water strainer	No fixed interval: Perkins leaves the weed trap in the sea-water intake to the skipper, depending on the water⁶⁵
Anode	Heat exchanger anodes: check regularly, replace before half the zinc is gone (dealer guideline)⁶⁸
Storage / winterising	Before a lay-up of several months: drain oil and coolant, renew the oil filter and refill, spray a little oil into the cylinders, seal the air intake and exhaust, store the battery charged, pack the impeller pump with grease (Perkins names Marfak 2HD, otherwise glycerine) and fill the fuel system with a preservation fuel⁶⁵

Perkins’ schedule from the workshop manual for the 4.108, 4.107 and 4.99 marine engines (publication 601 SER 0478 1088, 1978): hours or time, whichever comes first. Perkins publishes no operation manual for these engines online; paper copies of the workshop manual come from Perkins distributors. The shorter intervals for boats, the check before every start and the anode advice are dealer guidelines from Foley Engines, a Perkins dealer (Tech Tip 36).

Specifications

Cylinders	4, in-line, four-stroke, indirect injection (pre-combustion chambers in the cylinder head)^69,65
Displacement	1760 cc (Perkins rounds it to 1.8 l); bore 79.375 mm (3.125 in)^70,37
Bore × stroke	79.37 × 88.9 mm (3.125 × 3.5 in)^65,71
Compression ratio	22:1⁶⁵
Firing order	1-3-4-2⁶⁵
Direction of rotation	Anticlockwise viewed from the flywheel (Perkins: “left hand viewed from rear”), i.e. clockwise from the front⁶⁵
Power	Marine ratings (Perkins, 1978): 47 hp at 4000 rpm for fast pleasure craft, 45 hp at 3600 rpm for pleasure craft, 37 hp at 3000 rpm for commercial craft (shaft horsepower). Vehicle and industrial version: 55 bhp (41 kW) at 4000 rpm^65,71
Injection	Indirect injection; CAV DPA distributor pump; CAV injectors (holder BKB40SD5224, nozzle BDN12SD6236) set to 150 atm (about 152 bar), minimum working pressure 135 atm⁶⁵
Injection timing	Static timing 18° BTDC (fuel pump codes EH34E and PH30); the angles depend on the code stamped next to the injection pump’s data plate⁶⁵
Idle speed	625 rpm (Perkins: may vary with the application)⁶⁵
Valve clearance (cold)	0.30 mm (0.012 in), inlet and exhaust^72,65
Tightening torques	Cylinder head nuts 60 lbf ft (81 Nm); connecting rods 42 lbf ft (57 Nm); main bearings 85 lbf ft (115 Nm); flywheel 60 lbf ft (81 Nm); crankshaft pulley 150 lbf ft (203 Nm); injector nuts 12 lbf ft (16 Nm); threads lightly oiled^65,72
Engine oil capacity	Standard engines 4 l refill, 4.8 l total; Lowline engines 4.5 l refill, 5.3 l total. Fill to the dipstick mark; after an overhaul add about 1.4 l for pipes and filter⁶⁵
Oil pressure	30–60 psi (2.1–4.2 kgf/cm², about 2–4 bar) at maximum engine speed and normal operating temperature⁶⁵
Cooling	Fresh-water circuit with heat exchanger and header tank, sea water from a Jabsco 3270 impeller pump. Three factory layouts: early (header tank and heat exchanger in one unit at the front), Lowline (header tank at the front, heat exchanger at the rear) and later a Bowman exhaust manifold with built-in heat exchanger^73,1
Coolant capacity	7.4 l (13 imperial pints)⁶⁵
Thermostat opens at	75 °C for marine use (82 °C on automotive and industrial versions), according to a dealer; the 1978 workshop manual gives 69 °C, fully open at 87 °C, for heat-exchanger-cooled engines and 52 °C for engines cooled directly with sea water^74,65
Flow rate	Sea-water pump (Jabsco 3270): 40 l/min (8.9 US gal/min) at 1500 rpm⁸
Starting	CAV Thermostart (12 V) in the inlet manifold, fed with fuel from a small reservoir; later cylinder heads have glow plugs instead^65,53
Alternator	12 V: CAV/Lucas AC5 (55 A hot) or 11AC (43 A hot); some engines have a Lucas C40 dynamo (22 A). Starter motor Lucas M45G⁶⁵
Dry weight	With gearbox: 229–275 kg depending on cooling and gearbox, e.g. 236 kg sea-water cooled with mechanical direct-drive gearbox, 259 kg with heat exchanger and hydraulic reduction gearbox, 275 kg Lowline with heat exchanger and hydraulic reduction gearbox⁶⁵
Gearbox	Mechanically or hydraulically operated reverse gearboxes, direct drive or with reduction (1978 workshop manual); make and ratio are on the gearbox’s own plate⁶⁵
Max. installation angle	Under engine a yacht may heel up to 25° (e.g. motor-sailing to windward) if it is brought upright now and then so the valve gear gets oil⁶⁵
Engine number location	Stamped on the top edge of the cylinder-block face that carries the injection pump. Three systems: first seven digits (e.g. 7300269), then 108U… (e.g. 108U251), then up to 15 characters such as ED13541U510256D (ED = family and type, 13541 = parts list, U = built in the UK, 510256 = serial number, last letter = year, D = 1977)^65,75

Good to know

Read the full engine number before ordering anything: on a 4.108 it starts with ED. Perkins has several versions of many parts for the same engine type, so dealers ask for the number or the build list.⁷⁵
Four quick checks tell early and late engines apart, and with them which parts fit: the sea-water pump flange (six or four bolt holes), the exhaust elbow flange (five or four), the lift pump (two or four bolts) and whether the injection-pump levers sit in an upright tower or lie flat on top.⁷⁶
The 4.107 and 4.99 share the workshop manual with the 4.108 but not their insides: the 4.108 has thin-wall dry liners pressed into the block that cannot be rebored (worn bores get new liners), while the 4.107 and 4.99 have wet liners sealed with rubber rings at the bottom, a lower cylinder-head torque (42 instead of 60 lbf ft) and different injection timing. Order pistons, liners and gaskets by engine type.^65,71
To take the Jabsco sea-water pump off, undo only the four inner nuts. The outer nuts hold the adaptor plate on the timing case; if the plate moves, it has to be re-centred with the Perkins alignment tool, or the pump drive wears quickly.¹
Never let the sea-water pump run dry for more than about 30 seconds, and carry a spare impeller and cover gasket. A little grease on the new impeller helps the pump prime.¹
Many Perkins heat exchangers left the factory without zinc anodes. Fitting them on the sea-water and coolant sides and changing them before half the zinc is gone keeps pieces from breaking off and blocking the tube stack.⁶⁸
The header tank cap depends on the cooling layout: early and Bowman engines take a 60 mm winged cap, Lowline engines a larger 70 mm round one. Measure the old cap before buying.⁷³
The cast-iron exhaust outlet elbow is the weak spot of the marinised 4.108: it corrodes from the inside until it blocks, and the engine overheats. Check it whenever the engine runs hot; stainless steel replacements exist. Elbows differ with the exhaust flange (four or five studs) and the water connection (on top for Lowline, at the side for Bowman engines).^77,78,30
Oil dripping from behind the flywheel usually comes from the rope-type rear crankshaft seal, a known weak point, especially where the engine is installed at an angle. Perkins says to check the crankcase breather first, because pressure in the crankcase pushes oil past the seal; for a new seal, dealers sell braided PTFE kits that last longer than the original rope.^65,79,80

Videos & how-tos

Links to YouTube, nothing embedded. The maker’s own channel comes first; the rest are channels we found clear and correct for this model.

Where to find the engine serial number on a Perkins 4.108 Video Foley Engines · EN · 1 min
Removing and refitting the raw water pump on a Perkins 4.108 Video cruising yacht repairs & restoration · EN · 8 min
Adjusting the valves on a Perkins 4.108 marine diesel Video Sailing the West Wind · EN · 7 min
Replacing heat exchanger and sea-water cooling parts on a Perkins 4.108, part 1 (French) Video Voilier Pierrick II · FR · 11 min

Fitted in

Boats whose builder lists it as standard or optional equipment:

Moody 376 — Perkins 4.108 (Fitted to several boats in the 1986–87 build register, mostly for the agent Bay Yachts; the exhaust drawing of September 1987 names it, like the T80, as standard)
Tayana 37 — Perkins 4.108 (Option of the 1970s and 1980s: the 4.108(M), about 49 bhp, fresh-water cooled with British marinisation (Ta Yang, 1983))
Valiant 40 — Perkins 4.108 (One of the other engines used over the production run (Kretschmer); Practical Sailor names Westerbeke, Perkins and Volvo as the makes Valiant used)

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Sources

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