Honda Marine 120HP 4-Stroke Outboard Engine Parts

(12 products)

This page is for Honda Marine 120HP 4-Stroke outboard engines. It helps you find compatible parts and service information, with maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Honda collection. Scroll to the bottom of this page to start browsing parts for this engine, and use the Filter & Sort controls on the collection page to narrow results by horsepower, year range, and part category.

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How to Identify Your 120HP Model

Nameplate/serial plate: Look on the transom bracket or swivel bracket. The plate shows the model, serial number, and often shaft length.

4‑Stroke specifics: Confirm oil filter and lubrication parts by model code and serial, as changes can occur across year updates.

Platform clues: This HP class is commonly an inline‑4 4‑stroke; many routine parts overlap with adjacent 115–140 HP family models—verify with your serial number.

Engine/Platform Overview

Mid‑Range Inline‑4 4‑Stroke

Feature	Description
Configuration	Inline‑4 EFI 4‑stroke outboard, mid‑range power class suitable for a wide range of boats.
Common Models	Honda mid‑range 4‑stroke outboards in the ~115–140 HP family (model specifics vary by year/market).
Advantages	Smooth operation, solid mid‑range torque, good fuel economy, and broad parts availability.
Notes	Many routine service items (oil filter, spark plugs, anodes, water pump kits) are shared across adjacent HP models; confirm by model/serial and shaft length.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the official service manual and your specific model’s maintenance schedule.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Initial 20 hrs, then every 100 hrs or annually	Use marine 4‑stroke oil grade per manual; replace the oil filter at each oil change.	Oil Filters
Gear oil (lower unit)	Every 100 hrs or annually	Inspect for water intrusion (milky oil). Replace seals if contamination is found.	Honda Lower Unit Seal Kits
Spark plugs	Inspect at 100 hrs; replace ~300 hrs or as needed	Check gap and condition; replace sooner if fouled or misfiring.	Spark Plug
Fuel filter / water separator	Every 100 hrs or annually	Replace primary and inline filters; drain water separators regularly.	Fuel Filters
Water pump impeller/kit	Inspect annually; replace every 2–3 seasons (or 200 hrs)	Essential for cooling; replace sooner if stream is weak or after sand/silt ingestion.	Honda Water Pump Repair Kits
Anodes (sacrificial)	Inspect often; replace when ~50% consumed	Choose zinc (salt), aluminum (brackish/salt), or magnesium (fresh) per environment.	Anodes

Frequently Used Parts Categories

Routine Service: Service & Maintenance Kits
Cooling System: Honda Water Pump Repair Kits
Fuel System: Fuel Filters
Ignition / Electrical: Electrical Items
Corrosion Protection: Anodes
Propellers & Hubs: Propellers
Lower Unit / Gearcase: Honda Lower Unit Seal Kits

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak telltale stream or overheat alarm	Inspect intake screens for debris; verify impeller condition; test thermostat; check anodes for heavy corrosion.	Water pump kit, thermostat, intake screens, anodes
Poor acceleration or power loss	Check prop for damage/cavitation; replace clogged fuel filters; verify spark plug condition; confirm clean fuel and tank venting.	Propeller, fuel filter, spark plugs
Hard starting or rough idle	Confirm battery voltage and connections; inspect plugs; check for stale fuel; consider injector/throttle body cleaning.	Spark plugs, fuel filter, injectors, battery cables
Gearcase noise or metal in gear oil	Drain and inspect gear oil; look for fishing line on prop shaft; pressure/vacuum test seals.	Lower unit seal kit, bearings, prop shaft seals

FAQs

Are parts interchangeable between different years or mid‑range platforms?

Many routine items (oil filters, plugs, anodes, water pump kits) carry over across nearby HP models and years, but there are exceptions. Always confirm by model code, serial number, and shaft length before ordering.

When should I replace the impeller?

Inspect annually and replace every 2–3 seasons or ~200 hours. Replace immediately if you see a weak/erratic telltale, after sand/silt ingestion, or any overheat event.

How often should I change lower unit gear oil?

At least every 100 hours or annually. If the oil appears milky (water contamination) or smells burnt, change it sooner and pressure/vacuum test the gearcase.

What information helps confirm part compatibility?

Provide the model code, serial number, shaft length (L/XL), control type (remote/tiller), and the specific part location (e.g., “inline fuel filter on powerhead”). Photos of the nameplate and the part can also help.

Ready to find parts? Browse the main Honda collection and use Filter & Sort to narrow by horsepower, year, and model.

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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.