For commercial marine operators and engineers who demand continuous, reliable performance from their vessels, the YMR 6LA marine diesel engine has long been a trusted workhorse. Whether powering a fishing trawler, a coastal freighter, or a marine auxiliary genset, the engine's ability to sustain high-load operation for thousands of hours depends heavily on the integrity of its cylinder liners. The 748616-01901 Diesel Engine Cylinder Liner Sleeves are premium, OEM-grade replacement components engineered specifically for the YMR 6LA platform, delivering exceptional wear resistance, optimal heat transfer, and a precision fit that restores compression and minimises oil consumption.
1. Structural Features & Advantages of the 748616‑01901 Cylinder Liner
The 748616-01901 is far more than a simple cast-iron tube—it is a precision-engineered component meticulously designed to withstand the extreme mechanical and thermal stresses of marine diesel combustion. Its key design features include:
High-alloy chromium-molybdenum (Cr-Mo) cast iron – Manufactured from a specialised Cr-Mo alloy, this material offers superior resistance to adhesive wear (scuffing), abrasive wear, and thermal fatigue. The alloy is specifically formulated to maintain its hardness and dimensional stability at continuous operating temperatures up to 300°C on the inner bore surface, preventing the "bore softening" that plagues lower-grade liners.
Induction-hardened and plateau-honed running surface – The inner bore undergoes an induction-hardening process to achieve a uniform surface hardness of HRC 52–58, creating a durable wear layer that resists scoring from piston ring micro-movement even under peak firing pressures. The final finishing uses a multi-stage plateau honing process, producing a precise cross-hatch pattern (typically 30–45° included angle) with a surface roughness (Ra) of 0.15 – 0.30 µm. This optimises oil film retention, ensures rapid ring seating during break-in, and significantly reduces oil consumption over the liner's service life.
Wet-type liner with precision O-ring grooves – The 748616-01901 is a wet liner, meaning its outer surface is in direct contact with the engine coolant. It features accurately machined grooves at the lower sealing section, engineered to accommodate high-temperature FKM (Viton®) O-rings. This design maintains a positive coolant seal, preventing emulsification of the engine oil (coolant ingress) and keeping combustion gases out of the cooling system, which can otherwise cause overheating and cavitation erosion.
Advanced anti-cavitation & corrosion protection – The water-jacket contact area receives a specialised anti-cavitation coating and chemical passivation treatment. This robust surface protection resists pitting and material erosion caused by coolant vibration (cavitation) and the corrosive effects of seawater-contaminated coolants—a common failure point in marine applications.
Precision-ground top flange with controlled protrusion – The upper flange is ground to a mirror finish with micron-level flatness (typically ±0.02 mm), ensuring a perfect gas-tight seal against the cylinder head gasket. The liner protrusion (the height the liner stands above the block deck) is factory-set to 0.05 – 0.15 mm, a critical dimension that guarantees correct head gasket compression and prevents combustion gas leakage under heavy loads.
Operational advantages for marine engineers and fleet owners:
Reduced lubricating oil consumption – The optimal cross-hatch finish and bore geometry minimise oil bypass past the piston rings, reducing top-up frequency by up to 25% compared to worn liners.
Extended overhaul intervals – With correct fuel, air filtration, and coolant maintenance, this liner reliably delivers 10,000 – 15,000 hours of dependable service.
Consistent compression & thermal efficiency – A true, undistorted bore maintains maximum cylinder sealing, translating to better fuel economy, easier cold starting, and reduced visible smoke under load.
Protects against premature ring & piston wear – The correct bore hardness and surface finish extend the lifespan of expensive compression rings and pistons, reducing overall cost of ownership.
Direct drop-in fit – Identical to the original YMR 6LA part in all critical dimensions—no block re-boring or custom shimming required when using standard-size liners.
2. Compatible Engine Models & Typical Applications
The 748616-01901 cylinder liner sleeve is specifically engineered for the YMR 6LA marine engine series—a durable 6-cylinder, inline, 4-stroke, water-cooled diesel platform widely utilised in commercial and auxiliary marine power roles.
| Engine Model / Series | Typical Applications |
|---|
| YMR 6LA (Naturally Aspirated & Turbocharged) | Main propulsion for medium-sized fishing vessels, coastal freighters, harbour tugs, and pleasure craft |
| YMR 6LA-G (Genset Variant) | Prime and standby power generation on offshore platforms, fishing boats, and land-based marine terminals |
| Commonly used as aftermarket replacement | Directly compatible with Yanmar 6LA platforms (verify fitment with engine serial number) |
Critical cross-reference: The 748616-01901 is a recognised service part number for YMR 6LA cylinder liners. Oversize liners (+0.25mm, +0.50mm) are typically available depending on bore wear—always confirm your current cylinder bore measurement and engine serial number (e.g., 6LA-****) before ordering. This liner is generally supplied as a bare unit; O-ring seals, head gaskets, and piston rings must be ordered separately or as part of a complete overhaul kit.
3. Common Failure Modes & Installation/Replacement Recommendations
Typical Warning Signs That Your Liner Needs Replacement
Excessive oil consumption with blue exhaust – Continuous blue smoke at operating temperature indicates bore glazing, excessive wear, or deep vertical scoring that prevents the rings from properly scraping oil.
High blow-by and crankcase pressurisation – Oil mist pulsing from the dipstick tube or breather due to worn bore ovality or deep scuff marks from ring movement.
Unexplained coolant loss – Dropping coolant levels without visible external leaks often points to a failed lower O-ring seal or a cracked liner allowing coolant into the crankcase (milky oil emulsion).
Combustion gas in the cooling system – Persistent bubbles in the radiator or expansion tank indicate a cracked liner or failed upper seal allowing high-pressure combustion gases to enter the coolant.
Loss of compression / hard starting – Worn or scored liners reduce cylinder sealing, leading to difficult starts, rough idle, and an inability to reach full rated RPM under load.
Professional Installation Best Practices
Precision installation is crucial to realising the full service life of the 748616-01901 liner. Follow these essential steps:
Thorough cleaning of the cylinder block bore – Remove the old liner and meticulously clean the liner seat in the block using a suitable solvent and a non-abrasive nylon pad. Remove all old O-ring residue, carbon deposits, and surface rust. The seat must be perfectly clean, dry, and free from any foreign particles.
Inspect and measure the block housing – Using a dial bore gauge, measure the block's liner housing for ovality and out-of-round. Ensure it remains within service limits (typically less than 0.03 mm total variation). If the housing is worn beyond limits, an oversize liner or specialist block machining is required.
Lubricate and fit new O-rings – Lightly coat the new FKM (Viton®) O-rings (available separately or as a Rsolid kit) with clean engine oil or a specialised rubber assembly lubricant. Never use silicone grease or petroleum jelly, as these can cause the O-rings to roll or extrude, leading to immediate coolant leaks.
Install the liner with controlled, even pressure – Using a dedicated liner installation tool or a hydraulic press, insert the liner squarely into the block bore. Absolutely never strike the liner flange directly with a hammer, as this will distort the honed bore. Apply slow, steady, even pressure.
Measure liner protrusion – After seating, measure the liner's height above the block deck at three to four points around the circumference using a dial gauge and a suitable bridge piece. The protrusion must be consistent (typically 0.05 – 0.15 mm) and within the engine manual's specified range; the variance should not exceed ±0.03 mm. Incorrect protrusion will inevitably cause head gasket failure.
Final bore verification – Re-check the bore for roundness and taper to ensure no distortion occurred during the fitting process.
Assemble piston and rings – Fit the piston rings using a proper ring expander (never roll them over the skirt), stagger the ring gaps at 120° intervals, and thoroughly lubricate the piston, rings, and fresh liner bore with clean engine oil. Use a quality ring compressor to install the piston smoothly.
Torque the cylinder head – Follow the manufacturer's factory torque sequence and specifications (typically a multi-stage torque plus a final angle-tighten). Re-torque the head bolts after the engine has completed its initial heat cycle and again after the first 50 operating hours.
Proper break-in procedure – Start the engine and run at low idle (no load) for 15-20 minutes to allow the new rings to begin seating. Gradually apply load over the next 8-10 hours, avoiding sustained full-throttle operation. Change the engine oil and filter immediately after the initial break-in period to remove microscopic assembly debris.
4. Why Rsolid Engine Parts Is Your Preferred Global Supplier
Rsolid Engine Parts has been a premier supplier of Yanmar, Mitsubishi, and Caterpillar diesel components for over 15 years, servicing marine fleets, power stations, and engineering workshops across six continents. Here is why the 748616‑01901 cylinder liner from Rsolid is the intelligent procurement choice:
OEM-equivalent manufacturing standards – Produced in ISO 9001:2015 and IATF 16949 certified foundries, using the identical chromium-molybdenum alloy chemistry, induction-hardening processes, and plateau-honing techniques as genuine service parts.
100% precision quality inspection – Every single liner is inspected for bore roundness, straightness, surface finish (Ra value), hardness (HRC), and flange dimensions using state-of-the-art CMM equipment. We guarantee a perfect, distortion-free fit.
Complete complementary seal kits – We supply matching high-temperature FKM (Viton®) O-rings and full seal kits, ensuring you have everything required for a leak-free, reliable installation.
Global stock & rapid logistics – Strategically warehoused in Asia, Europe, and North America, ensuring 3-7 working day delivery to major international seaports and airports worldwide.
Competitive wholesale pricing – Attractive volume discounts are available for professional workshops, commercial fleet operators, and parts distributors. Please enquire about our bulk order and consolidated shipping options.
Free expert technical support – Our in-house marine diesel engineers provide installation torque guides, liner protrusion measurement advice, and remote troubleshooting via WhatsApp or email.
Unconditional warranty – 12 months / 2,000 operating hours against casting defects, premature wear, and material failures, supported by a straightforward return and expedited replacement policy.
Contact Rsolid Engine Parts Today
📧 Email: amy@rinjector.com
📱 WhatsApp: +86 15975376778
Whether you require a single 748616‑01901 liner for a running repair or a full set of six liners for a complete YMR 6LA overhaul, Amy and her dedicated team will respond with a detailed quotation, stock availability, and shipping schedule within 2 hours. We also supply complementary parts – piston assemblies, ring kits, connecting rod bearings, complete O-ring kits, and full gasket sets – for comprehensive engine rebuilds.
Choose the 748616‑01901 cylinder liner sleeve from Rsolid – engineered for uncompromising durability, minimal oil consumption, and reliable power delivery for your YMR 6LA marine diesel engine.
