Yamaha 15-20HP 4-Stroke Outboard Engine Parts

(4 products)

This page is tailored for Yamaha 4‑Stroke 15–20 HP outboard engines. Use it to find compatible parts and service information, including maintenance tips, commonly replaced components, and troubleshooting guidance. You can also browse the main Yamaha collection. Scroll to the bottom of the page to start browsing parts for this engine, and on the collection page use the Filter & Sort controls to narrow by horsepower, year range, and part category.

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How to Identify Your 15–20 HP Model

Find the nameplate/serial plate on the transom bracket or swivel bracket. Record the full model code and serial number.
Yamaha model codes for these engines often read like F15 or F20. Suffix letters/numbers indicate features such as shaft length (S=15", L=20"), start type (manual/electric), and control (tiller/remote).
4‑Stroke identifiers: look for an engine oil fill cap and an external spin‑on oil filter on the powerhead; EFI versions may also have a vapor separator/fuel rail rather than carburetors.
If your cover decals are missing, match by the stamped model code rather than appearance, as multiple versions share the same cowling style.

Engine/Platform Overview

Twin‑Cylinder 4‑Stroke (Carbureted)

Feature	Description
Configuration	Inline‑2, SOHC, carbureted 4‑Stroke, pull or electric start.
Common Models	Yamaha F15 variants; early F20 carbureted variants.
Advantages	Simple, light, easy to service; good fuel economy for small craft.
Notes	Many cooling and gearcase parts overlap with EFI versions; jetting and intake parts differ. Always confirm by model code and serial.

Twin‑Cylinder 4‑Stroke (EFI)

Feature	Description
Configuration	Inline‑2, SOHC, electronic fuel injection (EFI), improved cold starts.
Common Models	Yamaha F20 EFI variants.
Advantages	Smoother idle, reduced fuel consumption, better high‑altitude performance.
Notes	Water pump, anodes, and gearcase service items commonly interchange with carbureted versions; fuel system parts are EFI‑specific.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the official Yamaha service manual for your exact model and duty cycle.

Item	Interval*	Remarks	Parts Link
Engine oil + oil filter	Every 100 hours or annually	Use FC‑W 4‑stroke marine oil. Change first at 20 hours on new engines.	Yamaha Service & Maintenance Kits
Gear oil (lower unit)	Every 100 hours or annually	Inspect magnet for metal; service sooner if water intrusion is suspected.	Yamaha Lower Unit Seal Kits
Spark plugs	Inspect every 100 hours; replace as needed	Check gap and insulator color; replace if fouled or worn.	Spark Plugs
Fuel filter / water separator	Every 100 hours or annually	More frequent service in ethanol or contaminated fuel environments.	Fuel Filters
Water pump impeller / kit	Every 200 hours or 2 seasons	Replace sooner if weak telltale, overheating, or sand/silt use.	Yamaha Water Pump Repair Kits
Anodes (internal/external)	Inspect every 50 hours; replace when 50% depleted	Select material for your water (aluminum for brackish/salt, magnesium for fresh, zinc for traditional salt).	Yamaha Anodes
Thermostat	Inspect annually; replace 2–3 seasons	Stuck thermostats cause rich idle, poor economy, or overheat.	Yamaha Outboard Parts
Valve clearance check	Every 200 hours (or as specified)	May require cover gaskets on reassembly.	Yamaha Gaskets

Frequently Used Parts Categories

Routine Service: Yamaha Service & Maintenance Kits
Cooling System: Yamaha Water Pump Repair Kits
Corrosion Protection: Yamaha Anodes
Ignition / Electrical: Yamaha Starters
Fuel System: Fuel Filters
Propulsion: Yamaha Propellers
Sealing & Gaskets: Yamaha Gaskets

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak telltale or overheat alarm	Debris on intake screen, worn impeller, stuck thermostat, pinched outlet hose.	Water pump kit, thermostat, gaskets
Hard starting / rough idle	Stale fuel, clogged idle circuit (carb) or dirty filter (EFI), fouled plugs.	Spark plugs, fuel filter, gaskets
Poor acceleration / power loss	Damaged prop, incorrect pitch, restricted fuel flow, low compression on one cylinder.	Propeller, fuel filter, spark plugs
Gearcase noise or milky gear oil	Low gear oil, water intrusion past propshaft seals, fishing line on prop hub.	Lower unit seal kit, propeller hardware, gaskets

FAQs

Are parts interchangeable between F15 and F20 models?

Many cooling and gearcase items interchange, but fuel/air and calibration parts (carb jets, EFI components, intake) can differ. Always verify by full model code, suffix, and serial.

When should I replace the water pump impeller?

Every 2 seasons or ~200 hours is typical. Replace sooner if you run in sandy/silty water, the telltale weakens, or the engine shows overheat warnings.

How often should I change lower unit gear oil?

Service every 100 hours or annually, and immediately if the oil appears milky or you suspect seal damage.

What information helps confirm part compatibility?

Provide the full model code, serial number, shaft length (S/L), start type (manual/electric), control type (tiller/remote), and any known year range or EFI/carb detail.

Ready to find parts by model and horsepower? Browse the main Yamaha collection and use the filters to narrow by engine family and category.

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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.