Yamaha 4-Stroke 9.9-20HP Outboard Engine Parts

(5 products)

This page supports Yamaha 4‑Stroke 9.9–20 HP outboard engines. Use it to find compatible parts and practical service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse our main Yamaha outboard 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 9.9–20 HP Model

Nameplate location: Look on the port-side clamp/swivel bracket for the model/serial plate; a sticker may also be on the transom bracket.
Reading the code: Yamaha 4‑stroke models start with “F” (e.g., F9.9, F15, F20). Suffix letters indicate shaft length (S/L/X), start (M/E), tiller/remote, and other options.
Platform clues: Many F9.9/F15 and early F20 units are twin‑cylinder carbureted; later F20 versions may be EFI. Fuel system type affects filter, pump, and sensor compatibility.
Prop/hub note: Several 9.9–20 HP Yamaha models use an 8‑spline prop hub—verify spline count before ordering propellers and hardware.

Platform Overview

F9.9 / F15 (approx. 2003–2007)

Feature	Description
Configuration	Inline‑2 SOHC, carbureted 4‑stroke; manual or electric start; tiller or remote.
Common Models	F9.9 (short/long shaft), F15 (short/long, tiller/remote).
Advantages	Lightweight, quiet, and fuel‑efficient with widely available service parts.
Notes	Many service items interchange with sibling models. Prop hubs are commonly 8‑spline—confirm before purchasing props/hardware.

F20 (early carb; later EFI variants)

Feature	Description
Configuration	Inline‑2 4‑stroke; early units carbureted; some later markets received EFI. High‑thrust (FT) variants exist.
Common Models	F20 (S/L shafts, manual/electric), FT20 high‑thrust options.
Advantages	Stronger mid‑range torque and good charging output for small‑boat accessories.
Notes	Fuel system parts differ between carb and EFI. Prop hubs often 8‑spline—verify on your prop shaft before ordering.

Routine Maintenance & Service Parts

Intervals below are general guidelines for small Yamaha 4‑stroke outboards; always follow your engine’s official service manual.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Every 100 hours or annually	Use marine‑grade FC‑W oil; change more often for heavy trolling or harsh conditions.	Oil Filters
Gear oil (lower unit)	Every 100 hours or annually	Check for water contamination (milky oil). Replace seals if intrusion is found.	Yamaha Lower Unit Seal Kits
Spark plugs	Inspect 100 hrs; replace 200 hrs (or annually if fouled)	Confirm heat range and gap for your specific model/year.	Spark plug
Fuel filter / water separator (inline)	Every 100 hours or annually	Replace sooner with ethanol or contaminated fuel issues.	Fuel Filters
Water pump impeller / kit	Inspect annually; replace every 2 seasons (or ~200 hrs)	Shorter intervals for sandy/silty or shallow‑water use.	Yamaha Water Pump Repair Kits
Anodes (internal & external)	Inspect each season; replace when ~50% depleted	Match anode material (aluminum/zinc/magnesium) to water type.	Yamaha Anodes
Thermostat	Inspect every 2 years	Replace if stuck or corroded; critical for correct operating temp.	Yamaha Outboard Parts
Valve clearance check	Every 200 hours or 2 years	Adjust as needed; misadjustment can cause hard starting or noise.	Yamaha Outboard Parts

Frequently Used Parts Categories

Routine Service & Kits – Yamaha Service & Maintenance Kits
Cooling System – Yamaha Water Pump Repair Kits
Fuel System – Fuel Filters
Ignition / Electrical – Electrical Items
Gearcase & Sealing – Yamaha Lower Unit Seal Kits
Corrosion Protection – Yamaha Anodes
Propellers & Hardware – Yamaha Propellers

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak tell‑tale or overheat alarm	Inspect intake screens for debris, verify impeller condition, test thermostat operation.	Water pump kit, thermostat, intake screen
Poor acceleration / power loss	Check prop damage/slip, replace clogged fuel filter, inspect spark plugs; verify throttle/carb sync on carb models.	Propeller, fuel filter, spark plugs
Hard starting / rough idle	Drain stale fuel, confirm choke/enrichment, check for vacuum leaks, verify plug gap and idle speed.	Spark plugs, fuel filter, carburetor components
Gearcase noise or milky gear oil	Check oil level/color, inspect for fishing line at prop shaft, pressure/vac test for leaking seals.	Lower unit seal kit, bearings, gear oil
Battery not charging	Verify rectifier/regulator connectors and grounds; check fuses and charging output at idle and cruise rpm.	Rectifier/regulator, wiring connectors, fuse

FAQs

Are parts interchangeable across F9.9, F15, and F20 models?

Many routine service items (plugs, anodes, some filters, impellers) are shared, but carbureted vs. EFI F20 fuel parts and certain gaskets/sensors can differ. Always verify by model code, serial, and fuel system type.

When should I replace the water pump impeller?

Inspect annually and replace every two seasons (or sooner for sandy/shallow use). Replace immediately if water flow weakens, the stream is intermittent, or the engine overheats.

How often should I change lower unit gear oil?

At least every 100 hours or annually. If oil appears milky or contaminated, service seals and refill with fresh gear oil before further operation.

What information helps confirm part compatibility?

Provide the exact model code and serial number, shaft length (S/L/X), start/control type (manual/electric; tiller/remote), fuel system (carb or EFI for F20), and prop spline count.

Ready to find parts? Browse the main Yamaha outboard collection and filter by horsepower, year, and model to locate the right components for your engine.

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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.