Cummins Onan · Generator

Cummins Onan MDKA / MDKB / MDKD

The MDKA, MDKB and MDKD sets are Cummins Onan’s small marine diesel generators: a Kubota indirect-injection diesel with freshwater cooling through a heat exchanger, a raw-water pump and a wet exhaust, built on a drip pan and mostly inside a sound shield. The networked Quiet Diesel (QD) range comprises the MDKBH (4/5 kW at 50/60 Hz, Kubota Z482), the MDKBJ (6/7.5 kW) and MDKBW (8 kW) with the D722, and the 1500/1800 rpm MDKBL and Space Saver MDKBK (7/9 kW, D1105), MDKBM (9.5/11.5 kW) and MDKBN (11/13.5 kW, both V1505); the MDKDK–MDKDN, whose operator manual dates from 2015, are their D versions with the same engines and ratings. Older sets on this page are the e-QD MDKAU (4/5 kW) and MDKAV/MDKBG (7/9 kW), the MDKAL (7/9 kW) and the MDKUB (5.5/6.5 kW) — the spec sheets of the MDKUB, MDKAL and MDKAV date from 2001 — while Cummins’ 2021 brochure still lists the MDKBH, MDKBJ, MDKBW and MDKDK–MDKDN. Operator manual 981-0180 covers the MDKBH, A029Z105 the MDKBJ/MDKBW, 981-0181 the MDKBK–MDKBN from spec E and A052J727 the MDKDK–MDKDN; for the older sets only Cummins’ archived maintenance cards and spec sheets remain.

Manuals & documents

The links go to Cummins Onan’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 impeller541-1524 · 132-04931—541-1524: MDKBH. 132-0493: MDKBJ and MDKBW (2013 edition of card F-1576). On these small sets the raw-water pump is belt-driven; every cruise kit holds two impeller kits.
Raw water pump impeller541-15191Sierra 23-33102MDKBK, MDKBL, MDKBM, MDKBN and MDKDK, MDKDL, MDKDM, MDKDN; the same number on the 2008 and 2013 editions of card F-1576. Sierra 23-3310: one source, a dealer that lists it in place of 541-1519 for the MDKBK–MDKBN and MDKAL/AA/AB.
Raw water pump impeller132-03494,5,3Sierra 23-33003e-QD MDKAV and MDKBG (7/9 kW), per card F-1383b and Overton’s; the older card F-1229D lists 132-0349 as the impeller kit with cover and gasket for the MDKAD/E/F. Sierra 23-3300: one source, a dealer that names it as the replacement for 132-0349 on the MDKAV, MDKBG and larger e-QD sets.
Raw water pump impeller132-0415 · 132-0379 · 132-03114,5,6—132-0415: e-QD MDKAU (4/5 kW, the MDKBH’s predecessor). 132-0379: MDKAL, MDKAA, MDKAB; the impeller kit with cover and gasket is 132-0375. 132-0311: MDKUB, MDKWB; the kit with cover and gasket is 132-0310 — card F-1229D prints these two numbers the other way round for other models, so confirm by serial number with a dealer.
Engine oil filter185-7444 · 185-5835 · 185-58011,4,5,6—185-7444: MDKBH, MDKBJ, MDKBW and MDKAU — Cummins lists oil filter wrench 420-0577 for these sets. 185-5835: MDKBK–MDKBN, MDKDK–MDKDN, MDKAV, MDKBG and MDKAL/AA/AB, i.e. every 1500/1800 rpm set on this page. 185-5801: MDKUB, MDKWB.
Fuel filter (engine)149-2106 · A026K2781,4,5,8Sierra 23-77607149-2106: MDKBH, MDKBK–MDKBN, MDKDK–MDKDN, MDKAU, MDKAV, MDKAL and, from spec E, MDKUB/MDKWB. A026K278: MDKBJ and MDKBW (2013 card). Sierra treats the two as interchangeable and a Cummins Onan dealer’s MDKBH kit contains A026K278, so you may be given either; we found no official supersession notice. Sierra 23-7760: one source, a dealer whose fit list names the MDKAU, MDKAV and MDKBG, not the MDKB/MDKD sets.
Fuel pre-filter149-1914-019,5—30-micron element for the optional remote fuel filter/water separator kit A026M935 (MDKBH, MDKBJ, MDKBK–MDKBN); card F-1229D lists the same element for the remote filter on the MDKUB/MDKWB.
Raw water pump132-04308,10—Belt-driven bronze pump with pulley for the MDKBH; Diesel Pro also lists it for the MDKBJ and MDKBW. Not printed in the Cummins documents we could reach: the number comes from two dealers, a Cummins Onan dealer’s MDKBH maintenance kit and Diesel Pro’s replacement pump, so check it against your pump or with a dealer.
Glow plug185-5421 · 333-0802 · 185-71071,4,5—185-5421 (12 V): MDKBH, MDKBJ, MDKBW, MDKAU, MDKAV, MDKBG, MDKAL/AA/AB, MDKUB/WB and MDKBK–MDKBN up to spec D. 333-0802 (12 V): MDKBK–MDKBN from spec E and MDKDK–MDKDN. 185-7107: 24-V plug for MDKBK–MDKBN and MDKDK–MDKDN. Count: 2 on the MDKBH and MDKAU, 3 on the MDKAV/MDKBG and on the K and L sets, 4 on the M and N sets.
Anode (engine)130-44341,4,5—Zinc pencil in the heat exchanger: MDKBK–MDKBN, MDKDK–MDKDN, MDKAV, MDKBG, MDKAL/AA/AB and MDKUB/MDKWB from spec E. The MDKBH, MDKBJ, MDKBW and MDKAU have no zinc to replace. The MDKBK–MDKBN/MDKDK–MDKDN cruise kit holds two.
Seawater pump belt511-0197 · 511-02061,4,11—V-belt driving the raw-water pump; on the MDKBH its tension is set by swinging the pump out. 511-0197: MDKBH and MDKAU. 511-0206: MDKBJ and MDKBW (2013 card).
Drive belt185-6934 · 511-01831,4,5,6,12—185-6934: V-belt of the MDKBK–MDKBN, MDKDK–MDKDN, MDKAV, MDKBG and MDKAL/AA/AB; on the MDKBK–MDKBN it is tensioned by swinging the battery-charging alternator out. 511-0183: water pump belt of the MDKUB and MDKWB (card F-1229D).
Vented loop0541-0876-01 · 0541-0876-029,11—Cummins siphon break kits: 0541-0876-01 for the MDKBJ and MDKBK–MDKBN (and the larger MDKBP, MDKBR, MDKBS, MDKBV), 0541-0876-02 for the MDKBH, with pre-formed hoses and unions. Required when the exhaust-water mixer sits less than 15 cm (6 in) above the waterline.
Onboard spares kit0100-3478-58 · A029E631 · 0100-3478-5213,9,14,1—Cummins calls them cruise kits. 0100-3478-58: MDKBH — 2 oil filters, 2 fuel filters, 2 impeller kits, 1 V-belt, no zinc. A029E631: MDKBJ (with the oil filter wrench, per catalogue F-1379) and, per the 2013 card, MDKBW; no zinc. 0100-3478-52: MDKBK–MDKBN and MDKDK–MDKDN — as for the MDKBH plus 2 zinc pencils. In the MDKBH column card F-1576 prints 100-3478-08 (2008) and 100-3748-08 (2013), but leaflet F-1211K and catalogue F-1379 give 0100-3478-58 for the MDKBH and 0100-3478-08 for the older MDKAU, so order by serial number.
Onboard spares kit0100-3478-08 · 0100-3478-02 · 100-3478-074,14,5,6—Cruise kits for the older sets. 0100-3478-08: e-QD MDKAU. 0100-3478-02: MDKAV and MDKBG, and MDKAL/AA/AB spec A (card F-1229D). 100-3478-07: MDKUB/MDKWB spec E; spec A–D sets take 100-3478-01.

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

Service intervals

TaskInterval
Oil level checkBefore the first start of the day and every 8 h of running (QD sets): oil and coolant level, fuel, coolant and water leaks, exhaust hose, battery connections, sea-water strainer and CO alarms1,12
Engine oil changeOil and filter on the QD sets and the e-QD MDKAU/MDKAV: first change after 50 h, then yearly or every 200 h; twice as often on the MDKBK–MDKBN with high-sulphur fuel. MDKAL/AA/AB and MDKUB/WB: every 6 months or 200 h1,12,4,5
Fuel filterReplace yearly or every 500 h on the QD sets and the MDKAU, every 200 h on the MDKAV, every 6 months or 200 h on the MDKAL and MDKUB. Drain water from the filter(s) monthly or every 100 h (QD sets, MDKAL, MDKUB)1,4,5
Raw water impellerReplace yearly or every 500 h — the same on every set on this page1,4,5
AnodeReplace yearly or every 500 h on the sets with a zinc pencil (MDKBK–MDKBN, MDKDK–MDKDN, MDKAV, MDKAL, MDKUB); the QD operator manuals say inspect at that interval. The MDKBH, MDKBJ, MDKBW and MDKAU have none1,12,4,5
V-belt checkCheck tension monthly or every 100 h, looking for slippage, cracks and wear (QD sets)1
BatteryCheck monthly or every 100 h, following the battery maker’s advice (QD sets)1
Siphon breakCheck monthly or every 100 h (QD sets); replace it once it is crusted with deposits1,11
Motor brushesGenerator brushes and slip rings on the MDKBH, MDKBJ and MDKBW: check yearly or every 200 h (dealer job). MDKUB/WB: clean the brushes every 6 months or 200 h1,5
Valve clearanceAdjust every 800 h on the QD sets and the e-QD MDKAU/MDKAV (dealer job)1,4
Coolant changeReplace coolant, pressure cap and thermostat every 2 years (QD sets and e-QD MDKAU/MDKAV)1,4
Cooling systemMDKAL and MDKUB: flush and clean the cooling system yearly5
V-belt replaceDrive belt and generator bearing(s): replace every 5 years or 2000 h per card F-1576 (the MDKBK–MDKBN manual says inspect the bearing); dealer job1,12

From Cummins Onan’s Quiet Diesel maintenance card F-1576 (11/2013) and the operator manuals 981-0180 (MDKBH), A029Z105 (MDKBJ/MDKBW), 981-0181 (MDKBK–MDKBN) and A052J727 (MDKDK–MDKDN); the older sets from the e-QD card F-1383b (MDKAU, MDKAV) and the MDK-series card F-1229D (MDKAL, MDKUB). Dealer jobs follow the engine and generator service manuals, which Cummins only offers on QuickServe Online behind a login.

Specifications

ModelsSingle phase, 50 / 60 Hz: MDKBH 4 / 5 kW; MDKBJ 6 / 7.5 kW; MDKBW 8 kW; MDKBL and MDKDL 7 / 9 kW; MDKBK and MDKDK 7 / 9 kW as Space Saver without sound shield; MDKBM and MDKDM 9.5 / 11.5 kW; MDKBN and MDKDN 11 / 13.5 kW. Older: MDKAU (e-QD) 4 / 5 kW; MDKAV and MDKBG (e-QD, the BG as Space Saver) and MDKAL 7 / 9 kW; MDKUB 5.5 / 6.5 kW15,16,17,18,19,20,21,14,22,23,24
TypeKubota four-stroke diesel, indirect injection, water cooled, digital electronic governing. MDKBH: Z482, 2 cyl, 0.479 l (67 × 68 mm); MDKBJ and MDKBW: D722, 3 cyl, 0.719 l (67 × 68 mm); MDKBK, MDKBL, MDKDK, MDKDL: D1105, 3 cyl, 1.123 l (78 × 78.4 mm); MDKBM, MDKBN, MDKDM, MDKDN: V1505, 4 cyl, 1.498 l (78 × 78.4 mm). Older sets, whose spec sheets name no engine maker: MDKUB 2 cyl, 479 cc (67 × 68 mm); MDKAL and MDKAV 3 cyl, 1124 cc (78 × 78.4 mm)11,25,12,26,27,28,24,23,22
Rated speedMDKBH and MDKBJ: 2400 rpm (50 Hz) / 2900 rpm (60 Hz); MDKBW: 2880 rpm, 50 Hz only according to its operator manual; MDKBK–MDKBN, MDKDK–MDKDN, MDKAL, MDKAV: 1500 / 1800 rpm; MDKUB: 3000 / 3600 rpm11,25,12,26,23,22,24
Generator endMDKBH, MDKBJ, MDKBW: single bearing, 2-pole rotating field with brushes; MDKBK–MDKBN and MDKDK–MDKDN: single bearing, 4-pole rotating field, brushless; MDKAL and MDKAV: 4-pole, brushless; MDKUB: 2-pole revolving field11,25,12,26,23,22,24
Engine oil capacityMDKBH 2.1 l; MDKBJ and MDKBW 3.0 l; MDKBK, MDKBL, MDKDK, MDKDL 4.0 l; MDKBM, MDKBN, MDKDM, MDKDN 4.3 l; MDKAU 2.1 l; MDKAV and MDKAL 4.0 l; MDKUB 3.8 l (4 US qt)1,11,25,12,26,4,23,24
Engine oil gradeAPI CH-4 or better once the first 100 h of break-in are over; SAE 15W-40 multigrade recommended for year-round use (choose the viscosity by ambient temperature); the sets leave the factory with 15W-4011,1
Coolant capacityMDKBH 2.1 l; MDKBJ and MDKBW 3.1 l; MDKBK, MDKBL, MDKDK, MDKDL 4.0 l; MDKBM, MDKBN, MDKDM, MDKDN 5.0 l; MDKAU 2.1 l; MDKAV and MDKAL 4.0 l; MDKUB 2.2 l1,11,12,26,4,23,24
CoolantFully formulated ethylene-glycol coolant to ASTM D6210; shipped as a 50/50 water/glycol mix (protects to −37 °C); in warm climates and sea-water use Cummins recommends 60/40 water/glycol; distilled water is best11
Thermostat opens atMDKBK–MDKBN and MDKDK–MDKDN: 71 °C, fully open at 85 °C; pressure cap 48 kPa (7 psi). Coolant, pressure cap and thermostat are replaced every 2 years on all QD sets12,26,1
Fuel consumptionFull load, 50 / 60 Hz: MDKBH 1.9 / 2.3 l/h; MDKBJ 2.3 / 2.9 l/h; MDKBW 3.0 l/h (50 Hz); MDKBK, MDKBL, MDKDK, MDKDL 3.0 / 3.8 l/h; MDKBM, MDKDM 3.4 / 3.8 l/h; MDKBN, MDKDN 3.8 / 4.5 l/h; MDKAL 2.7 / 3.2 l/h; MDKAV 2.7 / 3.0 l/h; MDKUB 2.1 / 2.7 l/h11,25,12,26,23,22,24
Flow rateRaw water, 50 / 60 Hz: MDKBH and MDKBJ 15 / 19 l/min; MDKBK–MDKBN and MDKDK–MDKDN 18.9 / 22.7 l/min. Maximum lift for raw water and fuel 1.22 m (4 ft) on all QD sets11,25,12,16
Battery12 V; at least 300 CCA (MDKBH), 450 CCA (MDKBJ, MDKBW), 360 CCA (MDKBK, MDKBL), 500 CCA (MDKBM, MDKBN); 24 V starting optional on the MDKBK–MDKBN and MDKDK–MDKDN11,25,12,1
Dry weightMDKBH 166 kg with its housing (operator manual: 159 kg); MDKBJ 195 kg with housing; MDKBL 272 kg with sound shield, 252 kg without; MDKBK Space Saver 238 kg; MDKBM and MDKBN 315 kg with shield, 290 kg without; MDKAL 277 kg with shield, 238 kg without; MDKAV 272 / 252 kg; MDKUB 173 kg. Values from the spec sheets; operator manuals 981-0181 and A052J727 swap the K and L weights16,11,17,18,19,20,21,23,22,24
DimensionsL × W × H, housed unless noted: MDKBH 662 × 511 × 524 mm; MDKBJ 664 × 583 × 535 mm; MDKBL 911 × 566 × 593 mm; MDKBK Space Saver 823 × 479 × 560 mm; MDKBM and MDKBN 1033 × 566 × 593 mm; MDKAL 915 × 568 × 596 mm with shield, 826 × 479 × 562 mm without; MDKAV 911 × 566 × 593 mm; MDKUB 710 × 553 × 596 mm. Installation drawings: MDKBH 0500-4718; MDKBJ and MDKBW A029F006; MDKBK and MDKDK 0500-4753; MDKBL and MDKDL 0500-4752; MDKBM, MDKBN, MDKDM, MDKDN 0500-475416,17,18,19,20,21,23,22,24,11,25,12,26
Sound levelFull load at 1 m, 50 / 60 Hz: MDKBH 68 / 71 dB(A) and MDKBJ 69 / 71 dB(A), both built only with a housing; MDKBW 72.5 dB(A); MDKBL, MDKBM, MDKBN with sound shield 65 / 66 dB(A), the MDKBK/MDKDK Space Saver has none; shield optional on the MDKAL and MDKAV (65 / 66 dB(A)), standard on the MDKUB (69 / 71 dB(A))16,17,25,18,19,20,21,23,22,24
Max. installation angleMDKBH and MDKBJ: 20° continuous, 30° intermittent; MDKBK–MDKBN and MDKDK–MDKDN: 10° continuous, 22.5° intermittent11,25,12,26
Emissions60 Hz ratings of the MDKBH, MDKBJ and MDKDK–MDKDN certified to US EPA Tier 3 (2021 brochure)15

Good to know

  • Keep your set’s cruise kit on board — two oil filters, two fuel filters, two impeller kits and a belt, plus two zinc pencils for the MDKBK–MDKBN and MDKDK–MDKDN — and order it with model, spec letter and serial number from the nameplate, because the kit numbers changed from one generation to the next.9,13
  • If the old impeller is missing vanes, find the pieces before you restart — they lodge in the heat exchanger. Push the new impeller into the housing while twisting it in its running direction, and wet pump and impeller with water, soapy water or silicone lubricant: oil and grease attack the rubber. On the MDKBH the pump comes off first (belt guard, hoses, two bolts).11
  • Seven blinks after a shutdown mean the QD controller lost raw-water flow: check the seacock, strainer and impeller before trying again. Don’t keep cranking either — at cranking speed the exhaust flow is too weak to clear the water, and the engine can flood.1
  • A set whose exhaust-water mixer sits less than 15 cm (6 in) above the waterline needs a siphon break. Check it monthly and replace it once it is crusted with deposits — that shows it leaks, and a failing valve lets sea water siphon into the engine while the set is off.11,1
  • The small MDKBH, MDKBJ and MDKBW run at 2400–2900 rpm with a brush-type generator (brushes and slip rings checked yearly or every 200 h) and a belt-driven raw-water pump, so a slack belt also means poor cooling. The 1500/1800 rpm sets are brushless, but they have a zinc pencil in the heat exchanger that the small ones lack.1,11
  • Cummins warns that ordinary CH-4 oil keeps a new or rebuilt engine from breaking in properly and specifies API CH-4 or better only after the first 100 h, with SAE 15W-40 for year-round use. Avoid running without load during break-in, and do the first oil and filter change at 50 h.11,1

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. cummins.com/sites/default/files/2018-08/F-1576.pdf
  2. wholesalemarine.com/sierra-23-3310-impeller-kit-for-onan/
  3. overtons.com/sierra-impeller-kit-for-onan-engine-sierra-part-%2323-3300-327410.html
  4. web.archive.org/web/20101120164731/http://cumminsonan.com/www/pdf/marine/f-1383.pdf
  5. web.archive.org/web/20040806134355/http://www.onan.com:80/pdf/marine/marinepartscard.pdf
  6. web.archive.org/web/20101120164747/http://cumminsonan.com/www/pdf/marine/f-1229.pdf
  7. wholesalemarine.com/sierra-23-7760-fuel-filter-for-onan/
  8. citimarinestore.com/es/generador-marino-cummins-onan/21037-cummins-onan-marine-generators…
  9. web.archive.org/web/20101120164602/http://cumminsonan.com/www/pdf/marine/F-1379_g.pdf
  10. dieselpro.com/cummins-onan-sea-water-pump-1320430-mdkb-qd-marine-generators.html
  11. cummins.com/sites/default/files/2024-07/cummins-onan-manual-mdkbh.pdf
  12. cummins.com/sites/default/files/2024-07/cummins-onan-manual-mdkbk-lmnprtuv.pdf
  13. web.archive.org/web/20090320024704/http://www.cumminsonan.com:80/www/pdf/marine/f-1211.pdf
  14. web.archive.org/web/20090220074142/http://cumminsonan.com:80/www/pdf/marine/f-1379.pdf
  15. mart.cummins.com/imagelibrary/data/assetfiles/0060769.pdf
  16. web.archive.org/web/20101120204526/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  17. web.archive.org/web/20101120203928/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  18. web.archive.org/web/20101120203517/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  19. web.archive.org/web/20101120204134/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  20. web.archive.org/web/20101120204114/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  21. web.archive.org/web/20101120204258/http://cumminsonan.com/www/html/Common/pdf/specsheets/…
  22. web.archive.org/web/20100919122508/http://cumminsonan.com/www/pdf/specsheets/a-1432.pdf
  23. web.archive.org/web/20100919094706/http://cumminsonan.com/www/pdf/specsheets/a-1351.pdf
  24. web.archive.org/web/20051016132550/http://www.onan.com:80/pdf/marine/a-1350.pdf
  25. cummins.com/sites/default/files/2024-07/cummins-onan-manual-mdkbj-bw.pdf
  26. cummins.com/sites/default/files/2024-07/cummins-onan-manual-mdkdk-lmn.pdf
  27. cummins.com/generators/products/onan-marine-qd-45-kw-generator
  28. cummins.com/generators/products/marine-qd-135mdkdn-8147a

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