Tohatsu 4-Stroke 9.9-20HP Outboard Marine Engine Parts

(3 products)

This page focuses on Tohatsu 4-Stroke 9.9–20HP outboard engines and helps you find compatible parts and service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Tohatsu 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/section.

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How to Identify Your 9.9–20HP Model

Locate the identification plate: typically on the transom clamp bracket or swivel bracket; it lists model, serial number, and sometimes shaft length.
Read the model code: many 4‑stroke portables use prefixes like MFS followed by the horsepower (e.g., 9.9/15/20). Suffix letters/numbers indicate features such as shaft length, tiller vs. remote, and electric vs. manual start.
Platform clues: earlier units are carbureted; later units use EFI. Visual cues include a visible carburetor vs. an EFI throttle body and related wiring.
Confirm shaft length and controls: short/long/extra‑long shaft and tiller/remote control options affect driveshaft, shift/throttle cables, and rigging parts.

Engine Platform Overview

Portable 4‑Stroke Carbureted Platform

Feature	Description
Configuration	Compact inline twin‑cylinder 4‑stroke, carbureted induction (common on earlier 9.9–20HP models).
Common Models	9.9/15/20HP 4‑stroke portable models in carbureted form (e.g., MFS9.9/MFS15/MFS20, earlier generations).
Advantages	Lightweight, simple maintenance, reliable starting when tuned correctly.
Notes	Many service parts (impeller kit, anodes, spark plugs) are shared across 9.9/15/20 within the same generation; verify model code and shaft length before ordering.

Portable 4‑Stroke EFI Platform

Feature	Description
Configuration	Inline twin‑cylinder 4‑stroke with electronic fuel injection on later 15–20HP and certain 9.9HP variants.
Common Models	MFS9.9/MFS15/MFS20 EFI variants (model suffixes indicate EFI and options like electric start and remote control).
Advantages	Improved fuel economy, smoother idle, better cold‑start performance vs. carburetor models.
Notes	EFI models use different fuel system components and some sensors vs. carb models; match parts to the exact model code and serial number.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow your official Tohatsu service manual and local operating conditions.

Item	Interval*	Remarks	Parts Link
Engine oil & filter	Every 100 hours or annually	Warm engine before draining; replace crush washer if applicable.	Oil Filters
Gear oil (lower unit)	Every 100 hours or annually	Check for water intrusion (milky oil). Replace seals if contamination is found.	Tohatsu Outboard Parts
Spark plugs	Inspect every 100 hours; replace 200 hours or as needed	Replace if fouled, worn, or out of spec gap.	Spark Plugs
Fuel filter / inline filter	Every 100 hours or annually	Replace sooner if poor fuel quality or storage issues are suspected.	Fuel Filters
Water pump impeller / kit	Every 2 seasons (annually in sandy/silty water)	Restore cooling performance; replace housing/keys as needed.	Tohatsu Water Pump Repair Kits
Anodes (salt/freshwater)	Inspect monthly; replace when 50% eroded	Use correct material (aluminum/zinc/magnesium) for your water type.	Anodes
Thermostat inspection/replacement	Inspect every 2 years or if overheat occurs	Stuck thermostats cause cold running or overheating; replace gasket.	Tohatsu Outboard Parts
Propeller & cotter pin	Inspect each trip; service seasonally	Remove fishing line, check for dings, confirm correct pitch for load.	Propellers

Frequently Used Parts Categories

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

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak telltale stream or overheat alarm	Inspect intake screens, telltale hose, thermostat; verify impeller condition.	Water pump kit, thermostat, intake screen, anodes
Poor acceleration or power loss	Check prop damage/slip, fuel quality, clogged fuel filter, spark plug wear.	Propeller, fuel filter, spark plugs
Hard starting or rough idle	Prime bulb, confirm choke/EFI enrichment works, inspect plugs; on carb models, check idle mixture and air leaks.	Spark plugs, fuel filter, EFI components or carb repair kit
Gearcase noise or metal in gear oil	Verify proper gear oil level/condition; check for water (milky oil); inspect prop shaft seals.	Lower unit seal kit, shims/bearings as needed

FAQs

Are parts interchangeable between 9.9, 15, and 20HP models?

Many service parts are shared within the same platform generation, but EFI vs. carbureted fuel systems and options like shaft length, electric start, or remote control can change what fits. Always confirm with the exact model code and serial number.

When should I replace the water pump impeller?

As a rule of thumb, replace the impeller every two seasons, or annually if you operate in sandy/silty water, notice weak telltale flow, or after an overheat event.

How often should lower unit gear oil be changed?

At least every 100 hours or once per year. If you see milky oil, metal debris, or a leak at the prop shaft, change the oil and inspect seals immediately.

What information do you need to confirm part compatibility?

Please provide the full model code, serial number, shaft length (S/L/XL), and whether it’s tiller or remote with manual or electric start. Photos of the nameplate and the part in question are helpful.

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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.