748620-01901 Wear Resistant Cylinder Liner – Compatible With Yanmar 6AY Marine Diesel Engine
For marine engineers and fleet operators running the Yanmar 6AY series, the cylinder liner is the unsung hero of engine longevity. It must withstand thousands of hours of piston reciprocation, extreme combustion temperatures, and the corrosive marine environment – all while maintaining a perfect seal and efficient heat transfer. The 748620-01901 wear resistant cylinder liner is a premium, OEM‑grade replacement engineered specifically for Yanmar 6AY marine and generator diesel engines, offering exceptional durability, precise dimensional accuracy, and a direct drop‑in fit.
Whether you are performing a scheduled major overhaul or addressing a scoring issue in a single cylinder, this liner – often available as part of a complete repair kit or as a standalone component – restores compression, eliminates blow‑by, and extends your engine's time between overhauls. In this comprehensive guide, we explore its advanced metallurgy, compatible 6AY engine variants, common failure indicators, professional installation best practices, and why Rsolid Engine Parts is the global supplier you can trust.
1. Structural Features & Advantages of the 748620‑01901 Cylinder Liner
The 748620‑01901 is far more than a simple cast‑iron tube. It is a precision‑engineered component designed to meet Yanmar's exacting standards for high‑speed, high‑temperature marine duty cycles. Its key design features include:
High‑alloy wear‑resistant cast iron – Manufactured from a specialised chromium‑molybdenum‑boron (Cr-Mo-B) alloy cast iron, this material offers exceptional resistance to adhesive wear (scuffing), abrasive wear, and corrosion. The alloy chemistry is specifically formulated to maintain hardness at elevated operating temperatures (up to 300°C on the inner surface), preventing the bore from softening over time.
Induction‑hardened and plateau‑honed bore – The inner running surface is induction‑hardened to achieve a surface hardness of HRC 52‑58, providing a durable wear layer that resists scoring from piston ring micro‑movement. The final finishing process uses a multi‑stage plateau honing technique, which creates a controlled cross‑hatch pattern (typically 30‑45° included angle) with a surface roughness (Ra) of 0.15 – 0.30 µm. This optimises oil film retention for rapid ring seating during break‑in and reduces oil consumption throughout the liner's service life.
Precision‑machined wet liner design – As a wet‑type liner, the outer surface is in direct contact with the engine coolant. The 748620‑01901 features accurately machined O‑ring grooves at the lower section, designed to accommodate high‑temperature FKM (Viton®) seals. These grooves maintain proper coolant sealing, preventing coolant migration into the crankcase and combustion gases from entering the cooling system.
Corrosion‑resistant outer surface treatment – The external water‑jacket area receives a specialised anti‑cavitation coating or passivation treatment, which resists pitting and erosion caused by coolant vibration and chemical attack – a common failure mode in marine engines operating with seawater‑cooled heat exchangers.
Precision top flange – The upper flange is ground to a mirror finish with micron‑level flatness, ensuring a perfect seal against the cylinder head gasket. The correct liner protrusion (typically 0.05‑0.15 mm above the block deck) is maintained to exact specifications, guaranteeing optimal head gasket compression and combustion sealing.
Operational advantages for marine and genset operators:
Reduced oil consumption – The plateau‑honed finish and optimal roundness minimise oil bypass past the rings, cutting top‑up frequency by up to 20‑25% compared to worn liners.
Extended overhaul intervals – With proper fuel, air filtration, and coolant maintenance, this liner can achieve 10,000 – 15,000 hours of reliable service.
Consistent compression – A true, unworn bore ensures maximum cylinder pressure, translating to better fuel economy and reduced black smoke under load.
Prevents premature piston ring wear – The correct bore hardness and finish extend the life of compression rings, reducing overall rebuild costs.
Direct drop‑in compatibility – Identical to the original Yanmar part in all critical dimensions – no need for block boring or shimming. Available in standard and oversize variants.
2. Compatible Engine Models & Typical Applications
The 748620-01901 cylinder liner is specifically engineered for the Yanmar 6AY series – a family of inline 6‑cylinder, 4‑stroke, naturally aspirated or turbocharged diesel engines widely used in marine propulsion and stationary power generation.
| Engine Model | Typical Applications |
|---|
| Yanmar 6AYM-GE | Marine genset (prime power), small‑medium fishing vessels |
| Yanmar 6AYM-WET | Pleasure craft, yachts, coastal workboats |
| Yanmar 6AYM-MP | Main propulsion for freighters, harbour tugs, ferries |
| Yanmar 6AYM-ET | Standby generator sets, emergency fire‑pump drives, irrigation |
3. Common Failure Modes & Installation/Replacement Recommendations
Typical Warning Signs Your Liner Needs Replacement
High oil consumption with blue exhaust – Indicates bore glazing, excessive wear, or scoring that prevents the rings from properly scraping oil from the cylinder wall.
Excessive blow‑by – Pressurised crankcase gases (oil mist from the dipstick tube or breather) due to worn bore ovality or deep scuff marks.
Coolant loss without external leaks – Milky oil emulsion (coolant in oil) points to a failed lower O‑ring seal or a cracked liner allowing coolant into the crankcase.
Combustion gas in coolant – Bubbles in the radiator or expansion tank indicate a cracked liner or failed upper seal allowing high‑pressure gases into the cooling system.
Loss of power and rough running – Reduced compression from a worn or scored liner leads to hard starting, misfiring, and reduced load capacity.
Professional Installation Best Practices
Correct installation is critical for achieving maximum liner life. Follow these essential steps:
Clean the cylinder block bore – Remove the old liner and thoroughly clean the block's liner seat using a suitable solvent and a non‑abrasive pad. Remove all carbon deposits, old sealant, and rust. The seat must be perfectly dry and free of any foreign material.
Measure the block bore – Use a bore gauge to measure the block's liner housing for ovality and out‑of‑round. Ensure it is within service limits (typically less than 0.03mm variation). If the housing is worn, an oversize liner or block machining may be required.
Inspect and lubricate O‑rings – Lightly coat the new FKM O‑rings (purchased separately or as a kit) with clean engine oil or a specialised rubber lubricant. Never use silicone grease or petroleum jelly – these can prevent the O‑rings from seating correctly and cause coolant leaks.
Install the liner with care – Using a dedicated liner installation tool or a hydraulic press, insert the liner straight down into the block bore. Do not use a hammer directly on the liner flange, as this will distort the honed bore. Apply even, steady pressure.
Measure liner protrusion – After installation, measure the liner's height above the block deck at three or four points around the circumference using a dial gauge and a bridge piece. Protrusion should be consistent (typically 0.05 – 0.15 mm) and within the engine manual's specification – the variance should not exceed ±0.03 mm. Incorrect protrusion will cause head gasket failure.
Final bore check – After installation, re‑check the bore for roundness and taper to ensure no distortion occurred during fitting.
Assemble piston and rings – Fit the piston rings using a proper ring expander, stagger the gaps at 120°, and lubricate the piston and liner bore with clean engine oil. Use a ring compressor to insert the piston assembly smoothly.
Re‑torque cylinder head – Follow the factory torque sequence and specifications (typical for 6AY: stage torque + angle‑tighten). Re‑torque after the initial heat cycle and again after 50 operating hours.
Break‑in procedure – Run the engine at low idle (no load) for 15‑20 minutes, then gradually increase load over the next 8‑10 hours. Avoid sustained full‑load operation during break‑in. Change the engine oil and filter after the initial break‑in period.
4. Why Rsolid Engine Parts Is Your Preferred Global Supplier
Rsolid Engine Parts has been a trusted supplier of Yanmar, Mitsubishi, and Caterpillar diesel components for over 15 years, serving marine fleets, power plants, and workshops worldwide. Here is why the 748620‑01901 cylinder liner from Rsolid is the right choice:
OEM‑equivalent manufacturing – Produced in ISO 9001:2015 and IATF 16949 certified foundries, using the identical chromium‑molybdenum alloy chemistry and induction‑hardening processes as genuine Yanmar service parts.
100% precision inspected – Every liner is checked for bore roundness, straightness, surface finish (Ra value), hardness (HRC), and flange dimensions using advanced CMM equipment. We guarantee a perfect fit.
Premium O‑ring options – We supply matching high‑temperature FKM (Viton®) O‑rings and seal kits, so you have everything needed for a leak‑free installation.
Global stock, fast delivery – Strategically warehoused in Asia, Europe, and North America – typical delivery 3‑7 working days to major international ports and airports.
Competitive wholesale pricing – Volume discounts for workshops, fleet operators, and parts distributors. Ask about our bulk order and container shipping rates.
Expert technical support – Our in‑house marine engineers provide installation torque guides, protrusion measurement tips, and troubleshooting via WhatsApp or email.
Solid warranty – 12 months / 2,000 operating hours against casting defects, premature wear, and material failures – with a straightforward return and replacement policy.
Contact Rsolid Engine Parts Today
📧 Email: amy@rinjector.com
📱 WhatsApp: +86 15975376778
Whether you need a single 748620-01901 liner for a running repair or a full set of six liners for a complete Yanmar 6AY rebuild, Amy and her team will provide a detailed quotation, stock availability, and shipping schedule within 2 hours. We also supply complementary parts – piston assemblies, ring kits, connecting rod bearings, O‑ring seals, and complete gasket sets – for comprehensive engine rebuilds.
Choose the 748620‑01901 cylinder liner from Rsolid – engineered to deliver exceptional wear resistance, consistent compression, and reliable power for your Yanmar 6AY marine and generator engines.
