Yanmar · Inboard diesel

Yanmar 1GM10

The 1GM10 is the single-cylinder, 0.32-litre indirect-injection diesel of Yanmar’s GM series, rated at 9.1 hp at 3600 rpm (8 hp continuous) — the standard auxiliary in small sailing yachts and motorsailers of roughly 20 to 27 ft. Yanmar introduced it around 1984 as a 20 % up-rated 1GM with a heavier flywheel and almost the same size and weight (76 kg); the 1GM shares most service parts but has its own head gasket and air-filter element. All versions are cooled directly with seawater through a small rubber-impeller pump and carry one pencil zinc in the block; it was sold with the KM2P gearbox, as the 1GM10V V-drive and as the 1GM10C with the SD20 saildrive. Yanmar publishes no GM-series operation manual online, but the parts catalogue is available through dealers and still lists the engine with running changes up to 2018.

Manuals & documents

The links go to Yanmar’s own documents — some as archived copies of pages the maker has since taken down. We host no manuals or drawings.

Wear parts & part numbers

PartOEM numberAlso fitsNote
Raw water pump impeller128176-420712,3,1replaces 128176-42070replaces 128170-42070SVB 272501All 1GM and 1GM10 versions, engine-driven bronze pump: 6-blade neoprene impeller approx. 32 mm, 12 mm wide, 8 mm shaft. Yanmar’s current number is the kit 128176-42090 below; dealers still ship the impeller alone.
Impeller kit (with gasket)128176-420902,5,4replaces 128176-42080Parts4Engines P4E495201333714Current Yanmar kit (since 2018): the same impeller plus end-cover gasket 128170-42090. Parts4Engines also sells a full pump service kit (P4E49520134593) with seals and bearings.
Pump cover gasket128170-420902,7,8Parts4Engines P4E495201295906Paper gasket under the pump end cover, all 1GM/1GM10; included in kit 128176-42090 and in the genuine service kit. The Parts4Engines number is a set of five.
Pump cover O-ring24321-0003502—Not the cover (that has a paper gasket) but the O-ring 1A G35 between pump and gear case; renew whenever the pump comes off. The same ring seals the GM-series oil filler cap (parts catalogue).
Raw water pump128170-422002,9,10,11replaces 128170-42000—Complete pump, all 1GM10 versions (replaces 128170-42000 from serial E12740 1GM10 YMI / E01385 1GM10C / E01195 1GM10 / E00731 1GM10L); supplied with its mounting O-ring.
Engine oil filter119305-351702,12,13,14replaces 119305-35151replaces 119660-35150replaces 124450-35100—All versions. Short spin-on filter (68 × 65 mm); many engines left the factory with the longer 119660-35150 (80 × 75 mm) — the short one is Yanmar’s approved replacement. Same filter as 2GM20, 3GM30, 2YM15, 3YM20/30 and 3JH.
Fuel filter (engine)104500-557102,17,18Hengst E486KP-D45215Parts4Engines P4E4952013376516Element of the engine-mounted strainer 124790-55601, all versions; renew O-ring 24341-000440 with it. Same element as 2GM20/3GM30 and the YM series.
Fuel filter O-ring24341-0004402,19—O-ring 1A S44 of the strainer bowl; part of the genuine service kit.
Air filter128171-125402,20,21,22SVB 7908620Intake silencer element (silencer 128171-12500) for 1GM10, 1GM10C, 1GM10L and 1GM10VE per the 2013 catalogue. The older 1GM takes 128170-12540; one US dealer lists that number for the 1GM10 too.
Alternator V-belt128170-77350E2,25,26,24Gates (via Parts4Engines) P4E4952013077123SVB 1576724Belt HM29, approx. 735 × 13 mm (catalogue number 128170-77350): 1GM and 1GM10 with the Hitachi LR135 alternator before the catalogue break points (E00336 1GM10, E00341 1GM10C, E00218 1GM10L, E03691 1GM10 YMI), and again on the later Denso-alternator engines (from about 2013). The one belt drives alternator and raw water pump.
Alternator V-belt105582-777902,27,26,28Gates (via Parts4Engines) P4E4952013077023Belt HM31, approx. 788 mm (dealers also list 105582-77790E): 1GM10 from serial E00336 (1GM10C from E00341, 1GM10L from E00218, 1GM10 YMI from E03691) with the Hitachi LR135-126 alternator — roughly mid-1980s to about 2013. Not for Denso-alternator engines.
Thermostat105582-492002,30Parts4Engines P4E4952013031429All 1GM10 versions; same thermostat as the seawater-cooled 2GM20/3GM30. Fit with cover gasket 104211-49160 (the Parts4Engines number includes it).
Thermostat gasket104211-491602,31,32—One under the thermostat cover and one under the zinc-anode flange; all 1GM10 versions.
Anode (engine)27210-2002002,34,35Tecnoseal (via Parts4Engines) P4E4952013050933Pencil zinc 20 × 20 mm on an M8 stud, one per engine, screwed into flange 128170-09320 in the side of the block behind the alternator. Renew with gasket 123210-09310; the Parts4Engines kit includes washer and gasket.
Anode plug gasket123210-093102,36,37—Seal under the anode plug; De Dieseldokter sells anode and gaskets together as a 1GM/1GM10 anode set.
Exhaust mixing elbow128170-135302,38,39—Cast mixing elbow for 1GM, 1GM10 and the seawater-cooled 2GM20. Fit with gasket 128170-13201; later engines use the longer studs 128170-13600.
Exhaust elbow gasket128170-132012,41,42replaces 128170-13200Parts4Engines P4E49520130845401GM, 1GM10 and 2GM20 (replaces 128170-13200 from serial E10132 1GM10 YMI / E01035 1GM10C / E01032 1GM10 / E00349 1GM10L). Not the 3GM30 gasket.
Fuel injector728170-531002,43—Complete injector for 1GM/1GM10 (and per cylinder on 2GM20/3GM30); nozzle element 124770-53000 (dealers also list 124770-53001). Seats on two copper rings 124950-11450, O-ring 24341-000260.
Fuel lift pump105582-520102,45,46Parts4Engines P4E4952013052044Mechanical feed pump, all 1GM10 versions; gasket 121520-01851 (replaced 121520-01850). The Parts4Engines kit comes with the gasket.
Cylinder head gasket128171-019112,47replaces 128171-01330—1GM10 only (changed from serial E05917 1GM10 YMI / E00566 1GM10C / E00509 1GM10 / E00250 1GM10L). The 1GM uses 128170-01331, which does not fit the 1GM10 — one US dealer lists it for the 1GM10 anyway.
Valve cover gasket128170-113102,48—1GM and 1GM10; needed whenever the valve clearance is set.
Drain plug gasket22190-2400022replaces 43400-500570—24 mm seal washer of sump drain plug 105430-01690 (parts catalogue only; changed from serial E12740 / E01385 / E01195 / E00731).
Service kitSK-MARINE-00119,50Parts4Engines P4E4952013551349Genuine Yanmar kit for 1GM and 1GM10 (also sold as SK-MARINE-001-G): oil filter 119305-35170, fuel filter 104500-55710 with O-ring 24341-000440, impeller 128176-42071 and end-cover gasket 128170-42090. The Parts4Engines annual kit has oil filter, fuel filter and impeller kit.
Gasket set728171-926012replaces 728171-92600Parts4Engines P4E4952013084751Full set for the 1GM10 (changed from serial E10132 / E01035 / E01032 / E00349): head gasket 128171-01911, gear-case, sump, feed-pump, breather, bonnet, pump-cover and end-cover gaskets, seal washers. Not the 1GM set.

Numbers checked against the sources below on 12 October 2026. Always confirm against your serial number and exact type before ordering.

Service intervals

TaskInterval
Full serviceAt least yearly: engine oil and filter, fuel filter element, impeller (dealer guideline)49
Raw water impellerYearly (dealer guideline)1
Fuel filterYearly (dealer guideline)15
Air filterEvery 2 years (dealer guideline)20
V-belt replaceEvery 2 years, sooner if cracked or glazed (dealer guideline)24

Yanmar does not publish the GM-series operation manual online, so there is no official schedule here — these are dealer guidelines. The hour-based intervals (oil, valve clearance, injectors) are in the manual, which a Yanmar dealer can supply.

Specifications

Cylinders1, vertical, four-stroke52
Displacement0.318 l52
Bore × stroke75 × 72 mm52
CombustionIndirect injection (swirl pre-chamber)53
Power9.1 hp (6.7 kW) at 3600 rpm (max.); 8.0 hp (6.0 kW) at 3400 rpm (continuous)52
Maximum torque1.9 kgf·m (about 18.6 Nm) at 2800 rpm53
Rated speed3600 rpm (max. output); 3400 rpm (continuous rating)52
CoolingDirect seawater cooling with rubber-impeller pump; no heat exchanger on any version52
Engine oil capacityapprox. 1.3 l (dealer data sheet; fill to the dipstick mark)53
Engine oil gradeAPI CD, SAE 15W-4053
Gearbox oilKM2P: approx. 0.25 l of the same 15W-40 engine oil (dealer data sheet). 1GM10C: the SD20 saildrive takes 2.2 l (2.5 l long-reach) of API CC or better SAE 10W-30 engine oil per Yanmar’s SD manual53,54
Valve clearance (cold)0.2 mm intake and exhaust (cold)53
Injection pressure170 ± 5 kgf/cm² (approx. 167 bar)53
Compression pressure28–33 kgf/cm²53
Injection timing15° BTDC53
Starter motor12 V, 1.0 kW (128170-77010)53
Alternator12 V. Parts catalogue: Hitachi LR135 (35 A) on early engines, Hitachi LR135-126 from serial E00336, Denso 55 A on later engines and Denso 40 A from late 2016; the dealer data sheet quotes a 55 A Hitachi LR155-20 — check the label on yours2,53
Dry weight76 kg (1GM10 with KM2P); 90 kg (1GM10V)52
Dimensions547 × 410 × 485 mm (L × W × H)53
GearboxYanmar KM2P mechanical cone clutch (clutch assemblies 2.21, 2.62 and 3.22:1 in the parts catalogue); 1GM10V: KM3V V-drive52,2
Saildrive1GM10C: Yanmar SD20 (2.64:1, propeller up to 14 in)54
Fuel consumption215 g/hp·h (specific, dealer data sheet)53
Versions1GM10 (KM2P gearbox), 1GM10C (SD20 saildrive), 1GM10V/VE (KM3V V-drive), 1GM10L; the earlier 1GM shares most service parts2,52
PredecessorYanmar 1GM53
Years builtfrom c. 1984; still in the parts catalogue with running changes up to 2018, no official end date53,2
Direction of rotationCrankshaft counter-clockwise, propeller shaft clockwise (seen from astern)53

Good to know

  • Read the serial number before ordering a belt: engines before the catalogue break (E00336 for the 1GM10) and the Denso-alternator engines from about 2013 take the shorter HM29, engines from E00336 with the Hitachi alternator take the longer HM31. The one belt drives the alternator and the raw water pump, so carry a spare of the right length.26,2
  • Whatever impeller number an old invoice shows — 128170-42070, 128176-42070, 128176-42071, 128176-42080 or 128176-42090 — it is the same small 6-blade impeller for the same pump; the newest number is a kit with the end-cover gasket.2
  • There is only one pencil zinc, in the side of the block behind the alternator. Unscrew the plug and fit a new zinc with a new gasket once it is half gone — the engine is seawater-cooled, so this zinc is all the corrosion protection the block has.33
  • The 1GM and the 1GM10 are not identical: the 1GM10 has its own head gasket (128171-01911) and air-filter element (128171-12540). Impeller, belt, zinc, oil and fuel filters are shared.47,2
  • On a 1GM10C the SD20 saildrive is filled with engine oil (API CC or better, SAE 10W-30), not gear oil — the only SD20 installation where that applies. Capacity 2.2 l, 2.5 l for the long-reach unit.54
  • A raw water pump that drips is usually the shaft water seal, not the impeller; the pump can be rebuilt (seals, bearings, end cover) instead of replaced.4

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.

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Sources

  1. svb24.com/en/impeller-for-yanmar-1gm.html
  2. mecanique-plaisance-finistere.com/yanmar/pdfmoteur/1gm10.pdf
  3. dedieseldokter.nl/en_GB/a-50783789/yanmar-impeller/yanmar-128176-42071-impeller-yanmar-1g…
  4. parts4engines.com/products/yanmar-1gm10-raw-water-pump-impeller-service-kits
  5. dieselpartsdirect.com/ym12817642090
  6. parts4engines.com/products/yanmar-1gm10-water-pump-cover-plate-gasket-set
  7. dieselpartsdirect.com/ym12817042090
  8. svb24.com/en/p/gasket-set-seawater-pump-for-yanmar-1gm-1gm10.html
  9. dieselpartsdirect.com/ym12817042200
  10. parts4engines.com/products/yanmar-1gm-and-1gm10-raw-water-pump
  11. shop.tnorrismarine.co.uk/products/yanmar-1gm10-water-pump
  12. dieselpartsdirect.com/ym11930535170
  13. shop.tnorrismarine.co.uk/products/yanmar-oil-filter-yanmar-1gm10-yanmar-2gm20-yanmar-3gm3…
  14. parts4engines.com/products/yanmar-1gm10-oil-filter
  15. svb24.com/en/hengst-diesel-filter-for-yanmar-1-2-3-gm-series-ysm-7-12-ps-2-qm-15-20-30-an…
  16. parts4engines.com/products/yanmar-1gm10-fuel-filter
  17. dieselpartsdirect.com/ym10450055710
  18. dedieseldokter.nl/en_GB/a-50693864/yanmar-fuel-filter/yanmar-1gm10-yanmar-2gm20-yanmar-3g…
  19. shop.tnorrismarine.co.uk/products/yanmar-service-kit-for-1gm10
  20. svb24.com/en/air-filter-for-yanmar-1gm10.html
  21. dedieseldokter.nl/en_GB/a-66905209/air-filter/yanmar-1gm10-air-filter-yanmar-128171-12540/
  22. dieselpartsdirect.com/ym12817012540
  23. parts4engines.com/products/yanmar-1gm10-alternator-belt
  24. svb24.com/en/yanmar-v-belt-for-1-gm-inboard.html
  25. dieselpartsdirect.com/ym12817077350e
  26. dedieseldokter.nl/en_GB/a-51141146/yanmar-gm-v-belt/yanmar-128170-77350e-v-belt-alternato…
  27. dieselpartsdirect.com/ym10558277790
  28. shop.tnorrismarine.co.uk/products/105582-77790e-hm31-yanmar-1gm10-alternator-belt-1982-20…
  29. parts4engines.com/products/1gm10-2gm20-3gm30-thermostat-and-gasket
  30. dieselpartsdirect.com/ym10558249200
  31. dieselpartsdirect.com/ym10421149160
  32. shop.tnorrismarine.co.uk/products/yanmar-1gm10-anode-plate-gasket
  33. parts4engines.com/products/yanmar-1gm-and-1gm10-pencil-anode-kit
  34. dieselpartsdirect.com/ym27210200200
  35. dedieseldokter.nl/en_GB/a-52025408/anode/yanmar-1gm-yanmar-1gm10-zinc-anode-27210-200200/
  36. shop.tnorrismarine.co.uk/products/yanmar-1gm10-2gm20-and-3gm30-anode-seal
  37. dedieseldokter.nl/en_GB/a-67610155/anode/yanmar-1gm-yanmar-1gm10-zinc-anode-set/
  38. shop.tnorrismarine.co.uk/products/128170-13530-yanmar-1gm10-2gm20-exhaust-elbow
  39. dieselpartsdirect.com/ym12817013530
  40. parts4engines.com/products/yanmar-1gm-1gm10-2gm-2gm20-exhaust-elbow-gasket
  41. dieselpartsdirect.com/ym12817013201
  42. dedieseldokter.nl/en_GB/a-67607677/exhaust-bend/yanmar-1gm-yanmar-1gm10-2gm20-exhaust-ben…
  43. dieselpartsdirect.com/ym72817053100
  44. parts4engines.com/products/yanmar-1gm10-fuel-lift-pump
  45. dieselpartsdirect.com/yanmar-1gm-fuel-system
  46. shop.tnorrismarine.co.uk/products/yanmar-1gm10-fuel-feed-pump
  47. dedieseldokter.nl/en_GB/a-67687675/yanmar-1gm10-parts/yanmar-1gm10-head-gasket-yanmar-128…
  48. dieselpartsdirect.com/yanmar-1gm-other-parts
  49. parts4engines.com/products/yanmar-1gm10-annual-service-kit
  50. dedieseldokter.nl/en_GB/a-51159892/yanmar-gm-maintenance-set/yanmar-1gm-yanmar-1gm10-serv…
  51. parts4engines.com/products/yanmar-1gm10-gasket-and-seal-set
  52. web.archive.org/web/20031226022632/http://www.yanmar.com.au:80/marine/gm_series/gm_series…
  53. lsm-diesel.dk/2012/yanmar/tekniskdata_dk/1gm10tekniskdata.htm
  54. yanmar.com/media/global/com/product/marinepleasure/sailBoatPropulsion/operationmanualgear…

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