Yanmar 4-Stroke 375HP Marine Engine

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This page is for Yanmar 4-Stroke 375HP marine engines. Use it to find compatible parts and practical service information. Below you’ll find maintenance tips, frequently replaced parts, and troubleshooting guidance. You can also browse our main Yanmar collection at any time. Scroll 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.

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How to Identify Your 375HP Model

Locate the engine nameplate: commonly on the starboard side of the cylinder block or near the injection system; some common-rail models also have a label on or near the ECU cover. Record both the model code and serial number.
Check the marine gear (transmission) plate: Kanzaki or other gear tags list their own model and ratio; this is separate from the engine model and helpful when sourcing coupling, mounts, or seals.
Understand model codes: examples include 6LYA-STP/6LY2 variants (inline-6) or 8LV-370 (V8). Suffix letters typically indicate aspiration/rating and emissions variations.
Confirm platform: many 370–380 HP Yanmar packages are inline-6 turbocharged diesels; some installations in this power band are V8 common-rail. Match parts by exact model and serial.

Platform Overview

Inline-6 Turbo Diesel (e.g., 6LY family)

Feature	Description
Configuration	Inline-6, 4-stroke, turbocharged and aftercooled diesel; mechanical or early electronic fuel control depending on variant
Common Models	6LYA-STP (~370–375 HP), 6LY2A variants (ratings vary by duty)
Advantages	Strong mid-range torque, proven durability, compact length for repowers
Notes	Keep aftercooler and heat exchanger clean for temperature control; many filters and service items are shared across 6LY variants—verify by model and serial before ordering.

V8 Common-Rail Diesel (e.g., 8LV family)

Feature	Description
Configuration	V8, 4-stroke, turbocharged common-rail diesel with ECU control
Common Models	8LV-370 (nearby power class); verify exact rating and duty for part matching
Advantages	Smooth operation, low vibration, refined fuel control and emissions
Notes	Follow ECU service intervals; ensure intercooler and charge-air hoses are inspected for leaks to maintain boost and performance.

Routine Maintenance & Service Parts

Intervals below are general guidelines; always follow the official Yanmar service manual for your exact model, duty rating, and operating environment.

Item	Interval*	Remarks	Parts Link
Engine oil & filter	100 hours or annually	Use marine‑rated diesel oil; change filter every oil service	Yanmar Oil filters
Primary & secondary fuel filters	200 hours or each season	Replace sooner if fuel contamination or restriction occurs	Yanmar Fuel filters
Air filter / intake	Inspect 100 hours; replace as needed	Restricted intake causes black smoke and power loss	Yanmar Air filters
Raw water pump impeller	200 hours or 1–2 seasons	Replace proactively; carry a spare	Yanmar Service & Maintenance Kits
Cooling system anodes (pencil zincs)	Inspect every 3 months; replace as needed	Protects heat exchangers and coolers from corrosion	Anodes
Thermostat & cooler service	Every 2 years or as required	Clean heat exchanger/aftercooler; renew gaskets and seals	Yanmar Gaskets
Belts (alternator/sea water pump)	Inspect 100 hours; replace 200–300 hours or if worn	Check tension and glazing; carry a spare set aboard	Belt

Frequently Used Parts Categories

Routine Service: Yanmar Service & Maintenance Kits
Fuel System: Yanmar Fuel filters
Lubrication: Yanmar Oil filters
Cooling System: Impellers
Exhaust System: Yanmar Elbows
Turbo & Induction: Yanmar Turbos
Sealing Components: Yanmar Gaskets

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
High engine temperature / overheat	Raw water strainer, impeller condition, belt tension, heat exchanger and aftercooler fouling, thermostat operation	Water pump impeller kit, anodes, gaskets, belts, thermostat
Poor acceleration / low top RPM	Fuel filter restriction, air filter blockage, boost leaks, hull/prop fouling or overloading	Fuel filters, air filter, turbo hoses/clamps, turbocharger service
Hard starting / rough idle	Battery condition and cranking speed, fuel/air in lines, injector performance	Starters, fuel filters, hoses, injectors
Black smoke under load	Air intake restriction, over-propped boat, boost not building, sooted mixing elbow	Air filter, turbo hoses, injectors, exhaust elbow
White steam or water at exhaust	Inspect mixing elbow, raw water flow, and cooler leaks	Exhaust elbow, gaskets, impeller kit

FAQs

Are parts interchangeable between different years or platforms?

Many filters, belts, and some cooling parts are shared within the same engine family, but differences in rating, emissions, and fuel system (mechanical vs. common-rail) can change part numbers. Always confirm using the full engine model and serial number, and note the marine gear model separately.

When should the raw water impeller be replaced?

As a preventive measure every 200 hours or 1–2 seasons, whichever comes first. Replace sooner if you see reduced raw water flow, elevated temperatures, or impeller vane damage during inspection.

How often should I change engine oil?

Typical guidance is every 100 hours or annually. Heavy-duty, commercial, or high-temperature service may require shorter intervals—follow your Yanmar manual for your specific duty rating.

What information helps confirm part compatibility?

Provide the engine model and serial number, marine gear model/ratio, year of manufacture (if known), and a clear photo of the engine nameplate. Photos of the existing part and installation also help verify fit.

Ready to find parts? Browse the main Yanmar collection and filter by horsepower, year, and model to zero in on the components you need.

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