A crankshaft is the backbone of a diesel engine. It turns the push of every piston into rotation for the propeller shaft or the alternator, and it runs in the main bearings at every hour the engine is working. Replacing one is a major job, and the part itself is heavy, costly and slow to ship, so the order has to be right the first time. Eight crankshaft records are now in the Sea Keepers approved catalogue, covering Caterpillar, Cummins, FPT (Iveco) and Onan engines. This guide sets out what each record says and what to confirm before a crankshaft is shipped.
When a crankshaft must be replaced
Many crankshafts can be reground to an undersize and returned to service with matching undersize bearings. Replacement becomes the better choice when a crack is found by magnetic-particle testing, when journals have already been ground to the last permitted undersize, when a bearing failure has overheated and hardened a journal, or when the shaft is bent beyond the straightening limit. On a working vessel the time a regrind takes can also decide the matter, which is why owners of critical engines often keep a crankshaft on order.
Caterpillar C18 crankshaft assembly 189-4918
SK-00030-AV is the genuine Caterpillar crankshaft assembly 189-4918 for C18 engines, about 203 kg (447 lb). The record gives a 183.00 mm (7.205 in) stroke, rod journals of 89.980 to 90.020 mm, main journals of 120.63 to 120.67 mm and a flange with a centering ring, 12 bolts and 1 dowel. Suppliers cross-reference 189-4917, 195-0314 and 468-5119, and the Cat Reman alternative is 10R-4463, a C18 Reman upgrade-to-new crankshaft. No supersession was confirmed in the sources reviewed, so send the engine serial number and let the current number be checked.
Caterpillar C7.1 crankshaft 376-4074
SK-00035 is Caterpillar engine crankshaft 376-4074 for C7.1 engines, about 55 kg and 851.84 mm long. It is used in C7.1 crankshaft groups 374-6300, 348-3285 and 446-8957. Aftermarket data gives a 135.000 mm stroke, rod journals of 71.970 to 71.990 mm and main journals of 83.990 to 84.010 mm, with 374-9163 as a cross-reference. Applications include C7.1 marine engines and C7.1 generator sets such as DE150E0, DE200E0 and XQP150. A Cat Reman option is also offered.
Cummins ISX15 / QSX15 / X15 crankshaft 4925762 / 4393462
SK-00031 is the Cummins crankshaft assembly for 15-litre ISX15, X15 and QSX15 engines, about 172 kg (380 lb), supplied with gear, tone wheel and adaptor. The record gives a 6.653 in stroke, rod journals of 93.980 to 94.020 mm and main journals of 126.980 to 127.020 mm, with an 8-bolt neck and 12-bolt flange. Suppliers list many cross-references, including 4925761, 3681910, 3681911, 3608889, 4923646 and 5440758. A supersession from 4925762 to 4393462 has been reported but was not confirmed, so the engine CPL and ESN should decide the number.
Cummins 6B / 6BT / 6BTA 5.9 crankshaft 3908032
SK-00034-AV covers the Cummins 6B5.9 family, widely used in workboats and 6BT generator sets. In the Cummins parts list, assembly 3908032 is crankshaft 3929037 plus crankshaft gear 3929026, and suppliers list 5362424 as a cross-reference to the same shaft, along with 3907804, 3903828, 3905619 and 3863320. Supplier data gives a 120 mm stroke, 69 mm rod journals and 83 mm main journals. When ordering, say whether you need the bare crankshaft or the assembly with the gear already fitted.
FPT (Iveco) Vector 8 crankshaft 504022670
SK-00032 and SK-00033 both carry FPT part number 504022670, the crankshaft for Vector 8 V8 diesels, including the V08 ENT M marine engine and the GE Vector 650E generator set. It weighs about 136 kg and pairs with connecting rod assembly 504087778 (SK-00023-AV) on the same engine list. No supersession was found. On V8 engines two rods share each crankpin, so the rods and rod bearings should be inspected and ordered together with the shaft.
Onan (Cummins) generator crankshafts 185-7415 and 0104-2186
SK-00037-AV is Onan crankshaft 185-7415, supplied with ball and sleeve, for HDKAH, HDKAJ and HDKAK sets from Spec H, HDKAT, HDKAU and HDKAV from Spec E, and the MDKBJ marine generator. In the MDKBJ manual it forms assembly A030B478 with ball 185-5575 and sleeve 185-2033; earlier Spec A HDKA units used 185-6705 instead. SK-00038-AV is crankshaft 0104-2186 (also written 104-2186) for the Cummins X2.5-G2 engine in the C22D5 generator set, listed with main bearing set 0541-1538 and rear seal 0104-2116. The spec letter on the Onan nameplate decides which crankshaft fits.
Order the rear seal housing with the crankshaft
SK-00029 is the Onan (Cummins) crankshaft rear oil seal housing assembly 0104-2116 with joint, for X3.3 and X2.5 engines in C22 D5, C33 D5, C38 D5, C30 D6 and C35 D6 generator sets. It holds rear seal 0509-0494 and seals the back of the crankshaft against oil leaks. Whenever a crankshaft is changed, the front and rear seals, main and rod bearings, thrust washers and the crankshaft gear or key should be ordered at the same time; reusing a worn seal on a new shaft is a common cause of oil leaks after an overhaul.
Fitting checklist
Before fitting a new crankshaft, check the main bearing bores for size and alignment, clean every oil gallery in the block, and confirm that the new bearings match the shaft size (standard or undersize). Measure bearing clearance with plastigauge or a micrometer, check crankshaft end float against the manual, torque main and rod caps in the correct sequence, and prime the lube system before the first start. Run the engine at light load first, then re-check oil pressure, temperatures and for any knock.
Send a complete enquiry
For a quotation, give the engine make, model and full serial number (CPL and ESN for Cummins, spec letter for Onan), the part number you hold, the Sea Keepers code, whether you need the bare crankshaft or the full assembly, whether remanufactured parts are acceptable, the bearing size, documentation needs and the delivery port. The approved product pages below show the catalogue details for each item.
For the business buyer
Confirm the intended vessel or facility, operating environment, quantity and required approval before requesting a quotation. Capacity, coverage and service interval should be matched to the risk rather than selected by headline price.
For technical experts
Verify the delivered model against the maker reference, rating, dimensions, materials, operating limits and certification scope. Record the serial or batch number and retain the manufacturer datasheet, declaration, test report and maintenance instructions in the vessel file.
Product comparison
Compare alternatives on certified performance, compatibility, installation requirements, inspection interval, spares availability and total life-cycle cost. A lower unit price is not a like-for-like comparison when approval documents or service support differ.
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