A marine engine crankshaft is heavy equipment with several components. It is impossible to build single-piece crankshaft for giant engines. Large watercrafts sailing across the globe operate on colossal devices weighing over 100 tonnes. These are mainly fully built crankshafts comprising a systematic assortment of various intricate parts to ensure optimal performance.
Despite the gilt-edged material composition and robust construction, the exposure to thermal stresses, vibrations, and pressure makes the nautical crankshaft vulnerable to gradual wearing, damage, and failure. While periodical monitoring and maintenance are necessary, replacing the faulty parts when needed offers an extended equipment lifecycle. Marine engineers recommend possessing a set of vital crankshaft parts during voyages to avoid technical failure in extreme environments.
In this edition of our guide to marine crankshafts, we are dropping an overview of crucial crankshaft components and spare parts.
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Prime Main Engine Crankshaft Components and Their Significance
Flywheel Flange
The flywheel mounting flange connects the engine flywheel to the crankshaft. It exists on the end of the crankshaft to hold the flywheel securely at the proper position.
Main Bearing Journals
The main journals enable the marine engine crankshaft to rotate within the engine block. These journals are fixed in the saddle comprising a set of bearing inserts bolted to the engine block using bearing caps. Maintaining the accurate alignment of main bearing journals is crucial to ensure proper engine rotation around these parts without friction or mechanical stresses. These journals are usually round and hardened structures with smooth surfaces to eliminate friction within the engine block.
The bearing inserts are replaceable tractile structures compared to the hardiness of the journals and are prone to frequent wearing. These structures absorb contaminants to prevent penetration into the pricy crankshaft parts.
Main Engine Crankshaft Saddle
These are specific areas within the engine block that house the main journals. The saddles and the bearing inserts have tiny holes to allow a thin film of lubricating oil to prevent contact and friction during operation.
Main Bearing Cap
The main bearing cap is clamped to the journal for precise torque specification.
Crank Webs
Also called the crank net, it is a crucial part connecting the crankshaft to the main journal.
Counter Weight
The Counterweight is an integral marine engine crankshaft component that enhances smooth and efficient equipment operation. It creates crucial energy changes during the piston movement from the BDC to the TDC and vice versa. The heavyweight side moves to the lowest point when the piston is at the TDC. Conversely, the heavy side is positioned at the highest point when the piston moves to the BDC.
Oil Gallery
Marine crankshafts feature a unique circuit for smooth oil transfer from the main journal to the big end journal. The crank net has drill holes to allow oil transmission between the bearing and the journal. It occurs when the crankpin reaches the top position, and the combustion force drives the connecting rod to the bottom.
Marine Engine Crankshaft Oil Seals
The extension beyond the crankcase at either end of the crankshaft offers substantial room for leaking oil. Hence, high-quality oil seals are necessary to block the oil passage from the front and rear connections. These oil seals are of two types with distinct attributes:
Front-end Oil Seals
There is a front oil seal behind the timing gear and pulley. Front-end seals do not pose severe consequences during a failure.
Rear-end Oil Seals
These seals occur inside the flywheel and main bearing journal. The seal is pushed into a tiny opening existing between the engine block and the oil pan. It has a molded lip for the snap spring that holds the seal firmly and prevents oil from leaking from all sides.
Keyway
The keyway is a square slot built at the end of the rotating shaft. It is a grooved machine with a rotating part that allows a locking facility to firmly hold the sprocket, pulley, or flywheel in the proper place and eliminate slippage for optimum torque transfer.
Thrust Washer
The main engine crankshaft may have two or more thrust washers, usually located between the crankshaft saddle surface and the web. These washers protect the crankshaft from lateral movement. The thrust washers prevent longitudinal movement of the crankshaft and ease the clearance. It is primarily a part of the main bearing for most marine engine models.
Crankpin
A crankpin is a crucial marine crankshaft part for establishing a firm bonding between the crankshaft and the connecting rod. Crankpins, a.k.a. connecting rod journals, have a cylindrical surface to transfer the rotational force to the end of the connecting rod. The crankshaft must have a separate crankpin for each cylinder.
How to Find OEM Marine Engine Crankshaft Spare Parts
Buying nautical crankshaft parts is easy when you shop at Alfa Marine Spare Parts. Our e-store is the one-stop destination for marine engines and electrical machinery from Caterpillar, Cummins, Scania, Volvo Penta, Komatsu, Wartsila, Deutz, Detroit Deisel, and other renowned brands.
Keep scrolling to explore the best-selling crankshaft items at our store gallery:
YM-129001-02931 – Yanmar MAIN BEARING – 4TNV88-BDHQ / 4TNV88-BDHQ(T) / 4TNV88-BDSA (STD)
YM-129795-01800 – Yanmar FRONT CRANKSHAFT SEAL – 4TNV88-GNP / 4TNV88-XMS
YM-129648-01780 – Yanmar REAR CRANKSHAFT SEAL – 4TNV88-BPHB
YM-129120-01780 – Yanmar REAR CRANKSHAFT SEAL – 4TNV88-BDHQ / 4TNV88-BDHQ(T) / 4TNV88-BDSA
YM-129150-02931 – Yanmar THRUST BEARING – 4TNV88-BDHQ / 4TNV88-BDHQ(T) / 4TNV88-BDSA
T403464 – Perkins CRANKSHAFT – 2806
KRP3122 – Perkins MAIN BEARING – 2306 / 2806 / 2506TAG3 / 2506C / 2506TAG4
CH11379 – Perkins CRANKSHAFT OIL SEAL – 2306 / 2806 / 2506TAG3 / 2506C / 2506TAG4 (FRONT)
CH11304 – Perkins CRANKSHAFT OIL SEAL – 2306 / 2506 / 2806 / 2506TAG3 / 2506C / 2506TAG4 (REAR)
KRP3022 – Perkins CONNECTING ROD BEARING – 2806 / 2506TAG3 / 2506C / 2506TAG4
T417566 – Perkins MAIN BEARING – 1206E-E70TTA / 1206F-E70TTA (STANDARD)
U5MB0030 – Perkins MAIN BEARING KIT – 6.354 / 1000 / 1006
U5MB0030A – Perkins MAIN BEARING KIT – 6.354 / 1006
ZZ90229 – Perkins CRANKSHAFT KIT – 1000 / 1006
ZZ90238 – Perkins CRANKSHAFT KIT – 4.236 / 1000
ZZ90183 – Perkins CRANKSHAFT KIT – 900
ZZ90179 – Perkins CRANKSHAFT KIT – 3.152 / 900 (WITH BEARINGS)
ZZ90178 – Perkins CRANKSHAFT KIT – 3.152 / 900
T418368 – Perkins CRANKSHAFT – 854E / 854F
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