Yanmar 4-Stroke 260HP Marine Engine

(3 products)

This page supports owners and technicians working on Yanmar 4‑Stroke 260HP outboard engines and comparable inboard diesel installations, helping you locate compatible parts and essential service information. Inside you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse our main Yanmar collection for a wider selection. Scroll down to the bottom of this page to start browsing parts for this engine, and on the collection page use the Filter & Sort controls to narrow results by horsepower, year range, and part category.

Browse All Yanmar Parts

How to Identify Your 260HP Model

Nameplate/serial label: Look on the engine block or rocker cover for the Yanmar ID plate; for sterndrive installations, a secondary tag may be on the transmission or mounting bracket.
Reading the model code: Example “6BY260” indicates a 6‑cylinder BY‑series, approximately 260 mhp. Suffixes often denote emissions generation, control type, or gear pairing (shaft vs. sterndrive).
Platform distinctions: BY‑series engines are common‑rail, turbocharged 4‑stroke diesels with high rated rpm; some similar‑power mechanical inline‑six platforms (e.g., 6CH) run lower rated rpm. Parts (filters, anodes, impellers) differ by platform.
Confirming compatibility: Record the full model code, serial number, gear/transmission model, and any ECU label info before ordering service parts.

Platform Overview

Yanmar 6BY260 (Common‑Rail Inline‑6)

Feature	Description
Configuration	Inline‑6, 4‑stroke diesel, common‑rail direct injection, turbocharged with intercooler; fresh‑water heat exchanger cooling.
Common Models	6BY260 series variants (shaftdrive and sterndrive options were commonly offered).
Advantages	Smooth running, strong mid‑range torque, good fuel economy, compact size for the output class.
Notes	Service with BY‑series specific filters and anodes; observe fuel system cleanliness (fine filtration is critical with common‑rail).

Comparable Mechanical Inline‑6 (6CH family, similar power range)

Feature	Description
Configuration	Inline‑6, 4‑stroke diesel, mechanically governed direct injection; turbo/intercooler options by rating.
Common Models	6CH models in the 255–280 hp range (M/L ratings). Parts and service intervals vary by duty rating.
Advantages	Proven workboat durability, straightforward mechanical service.
Notes	Use platform‑specific filters, impellers, and anodes; verify rating (M/H/L) when selecting parts.

Routine Maintenance & Service Parts

Intervals below are typical guidelines for 4‑stroke marine diesels; always follow the official Yanmar service manual for your exact model and duty rating.

Item	Interval*	Remarks	Parts Link
Engine oil & filter	Every 100 hours or annually	Use marine‑grade diesel oil; replace the spin‑on oil filter each service.	Yanmar Oil Filters
Fuel filters (primary & secondary)	Inspect every 50 hours; replace 200 hours or annually	Keep spare elements onboard; water contamination is a common cause of power loss.	Yanmar Fuel Filters
Raw‑water impeller	200 hours or every 2 seasons	Replace sooner if stream weakens or after any overheat event.	Impellers
Cooling system anodes (heat exchanger, aftercooler)	Inspect every 50–100 hours; replace as needed	Check more often in warm/salty water; protect coolers and block from corrosion.	Anodes
Air filter/cleaner	Inspect 100 hours; replace 200–300 hours	Restricted intake increases smoke and reduces boost.	Yanmar Air Filters
Serpentine/alternator belt	Inspect 100 hours; replace 2 years or on wear	Adjust tension; replace if cracked or glazed.	Belts
Coolant & thermostat	Coolant 2 years; thermostat inspect annually	Maintain proper corrosion inhibitors and opening temperature.	Yanmar Service & Maintenance Kits
Gear/drive oil (if sterndrive)	Every 100 hours or annually	Change more frequently after water intrusion or heavy use.	Yanmar Collection
Starter/battery checks	Inspect every 50–100 hours	Ensure strong cranking; poor voltage causes ECU and injector issues.	Starters

Frequently Used Parts Categories

Routine Service: Yanmar Service & Maintenance Kits
Fuel System: Yanmar Fuel Filters
Cooling System: Water Pumps and Impellers
Lubrication: Yanmar Oil Filters
Air & Turbo: Yanmar Air Filters and Yanmar Turbos
Exhaust & Elbows: Yanmar Elbows
Corrosion Protection: Anodes

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak water stream or overheat alarm	Inspect seawater strainer, intake screen, and raw‑water pump; verify thermostat operation and cooler anodes.	Water pump impeller kit, thermostat, anodes, intake screen/seacock service
Poor acceleration or power loss	Check for clogged fuel filters, water in fuel, restricted air filter, boost hose leaks, sooted exhaust elbow.	Fuel filters, air filter, turbo clamps/hoses, exhaust elbow
Hard starting or rough idle	Verify battery voltage and connections, prime/bleed fuel system, inspect for air leaks at filter heads.	Batteries/cables, starters, fuel filters, seals/gaskets
Black smoke or excess soot	Check air filter restriction, aftercooler cleanliness, turbo boost integrity, and exhaust backpressure.	Air filter, turbo, clamps/hoses, exhaust elbow
Drive noise or slipping (sterndrive installations)	Inspect gear oil level/condition, propeller for damage/fouling, and bellows/U‑joint condition.	Gear oil, propeller, bellows, seals

FAQs

Are parts interchangeable between different years or platforms (BY vs. CH)?

Many wear items look similar, but filtration, anodes, and cooling components often differ by platform and rating. Always confirm the full engine model code, serial number, and gear type before ordering.

When should the raw‑water impeller be replaced?

As a preventive measure, replace every 200 hours or every two seasons—whichever comes first—or immediately after any overheat or dry‑run incident.

How often should gear oil be changed on sterndrive setups?

Typically every 100 hours or annually. If you find water intrusion or metallic debris, service immediately and inspect seals and bellows.

What information do you need to confirm part compatibility?

Please provide the engine model (e.g., 6BY260), full serial number, gear/transmission model (shaftdrive or sterndrive), and the part you’re replacing. Photos of the ID plate and the existing part help ensure a perfect match.

Ready to find parts by horsepower, year, and model? Browse our main Yanmar collection and use the Filter & Sort tools to quickly narrow to your 260HP setup.

Shop the Yanmar Collection

If you’re unsure about your model, send us a clear photo of the nameplate and the part you need—we’ll help verify compatibility.