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Yamaha 2-Stroke 120HP Outboard Marine Engine Parts

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This page is tailored for Yamaha 2-Stroke 120HP outboard engines and helps you find compatible parts and key service information. Inside you’ll find maintenance tips, commonly replaced parts, and troubleshooting guidance. You can also browse our main Yamaha collection. 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 120HP Model

  • Locate the identification plate or decal on the transom bracket or swivel bracket (typically port side). It lists the model code, serial number, and sometimes shaft length.
  • Read the model code suffix: common letters denote shaft length (S/L/XL), control type (tiller/remote), and market year. The exact format varies by production year.
  • Confirm it’s a 2‑stroke: look for an oil injection tank/system or instructions for premix on the cowling. 2‑strokes have no crankcase engine oil changes.
  • Platform clues: mid‑range Yamaha 2‑strokes in this class were commonly V4 carbureted units; some markets may show inline‑4 variants. Count plug leads and carb bodies to help identify.

Engine Platform Overview

V4 Carbureted 2‑Stroke (common for this horsepower class)

Feature Description
Configuration V4, carbureted 2‑stroke with separate oil injection (Autolube) on many models
Common Models 120HP 2‑stroke variants in the mid‑range family (year/market dependent)
Advantages Strong mid‑range torque and punchy acceleration; relatively light for the output
Notes Some ignition, cooling, and gearcase parts may overlap with adjacent HP ratings in the same era; always verify by exact model code and serial.

Inline‑4 2‑Stroke (select markets/years)

Feature Description
Configuration Inline‑4 2‑stroke, typically carbureted; oil injection or premix depending on model
Common Models 120HP 2‑stroke inline‑4 variants (market/year specific)
Advantages Smooth delivery, straightforward carb service, good power‑to‑weight
Notes Carburetor sizes/jets and ignition components can differ by region; confirm parts by model code and carb ID where applicable.

Routine Maintenance & Service Parts

Intervals below are general guidelines for Yamaha 2‑stroke outboards. Always follow the official service manual for your exact model, year, and operating conditions.

Item Interval* Remarks Parts Link
Gear oil (lower unit) Every 100 hours or annually Inspect for water intrusion/metal. Replace gaskets; service seals if contaminated. Yamaha Service & Maintenance Kits
Spark plugs Inspect 50 hours; replace ~100 hours or as needed Use correct heat range and gap; replace sooner if fouled from rich running or trolling. Spark Plugs
Fuel filter(s) Inspect 50 hours; replace 100 hours/annually Include under‑cowl inline filter and any boat‑mounted water‑separating filter. Fuel Filters
Water pump impeller/kit 200 hours or every 2–3 seasons (sooner in sandy/silty water) Replace full kit if wear plate/cup is scored; verify strong tell‑tale after service. Yamaha Water Pump Repair Kits
Internal & external anodes Inspect 50 hours; replace when ~50% depleted Match alloy to water type (salt/brackish/fresh). Clean contact surfaces. Yamaha Anodes
Oil injection system check (or premix) Check each season Verify pump linkage, tank screen, and hoses on injected models; premix models typically run 50:1 unless specified otherwise. Yamaha Outboard Parts
Thermostat Every 2–3 years, or if running too cool/hot Stuck‑open stats cause cold running and excess smoke; stuck‑closed can overheat. Yamaha Outboard Parts
Propeller & hub inspection Each season and after impacts Check for dings, hub slippage, and shaft seal damage from fishing line. Propellers

*Intervals assume normal recreational use; adjust for heavy duty, commercial, or harsh conditions.

Frequently Used Parts Categories

Common Symptoms & Quick Checks

Symptom Check First Related Parts
Weak tell‑tale or overheat alarm Inspect intake screens, pump impeller, and thermostat; verify hose routing after service. Water pump kit, thermostat, intake screen, gaskets
Poor acceleration / power loss Check fuel quality, water in separator, clogged filters, carb sync/idle mixture, and ignition condition. Fuel filters, spark plugs, carburetor components, fuel lines
Hard starting / rough idle Verify choke/enrichment function, primer bulb integrity, plug gap, and air leaks at fuel fittings. Spark plugs, fuel filter, primer bulb/lines, choke/enrichment parts
Excessive smoke Confirm premix ratio or injection setting, thermostat operation (engine reaching temp), and prolonged cold idle. Thermostat, spark plugs, oil pump/linkage, fuel/oil hoses
Gearcase noise or metal in gear oil Check prop for fishing line, drain oil to inspect for water/metal, verify correct shimming after service. Gear oil, drain/fill gaskets, lower unit seal kit, bearings

FAQs

Are parts interchangeable across different years or platforms?

Some components in this horsepower range are shared with adjacent Yamaha 2‑stroke models from the same era, but ignition, carburetion, and cooling pieces often vary by model code and market. Always verify fit by the exact model/serial and shaft/control options.

When should I replace the water pump impeller?

Replace the impeller every 200 hours or 2–3 seasons, and sooner if you run in sandy/silty water or notice a weak tell‑tale. Use a full kit when the wear plate or housing shows scoring.

How often should lower unit gear oil be changed?

At least annually or every 100 hours. Inspect the drained oil for water (milky color) or metal particles. If water or metal is present, replace drain/fill gaskets and consider a seal kit service.

What information helps confirm part compatibility?

Provide the model code, serial number, shaft length, control type (tiller/remote), and country/market. Photos of the nameplate and the part being replaced also speed up verification.

Ready to find parts by horsepower, year, and model? Browse our main Yamaha catalog to locate components that fit your Yamaha 2‑Stroke 120HP outboard.

Shop Yamaha Outboard Parts

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.
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