Tohatsu 4-Stroke 8-9.9HP Outboard Engine Parts

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This page is dedicated to Tohatsu 4-Stroke 8–9.9HP outboard engines. Use it to find compatible parts, routine service information, maintenance tips, common replacement items, and troubleshooting guidance. You can also browse our 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 or section.

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How to Identify Your 8–9.9HP Model

Locate the ID/serial plate on the transom clamp bracket (typically starboard side) or on the swivel bracket. The sticker shows the model code and serial number.
Model codes for 4-stroke units commonly begin with “MFS” (e.g., MFS8, MFS9.8, MFS9.9). Suffix letters indicate features: S/L for 15/20 in shaft, E for electric start, and remote/tiller variants.
Platform clues: Carbureted versions have a manual choke/primer and mechanical carb; EFI versions reference an ECM in wiring and parts lists. All engines here are 4-stroke, twin-cylinder outboards.
Shared components: Many cooling and gearcase parts interchange between 8HP and 9.8HP models; verify by model code and serial for best fit.

Platform Overview

MFS8 / MFS9.8 Carbureted 4‑Stroke

Feature	Description
Configuration	Inline-2, SOHC 4-stroke, carbureted; manual or electric start; tiller or remote options.
Common Models	Examples include MFS8 (S/L) and MFS9.8 (S/L) with various electric start/remote suffixes.
Advantages	Lightweight, simple maintenance, very good fuel economy for displacement hulls and tenders.
Notes	Water pump kits, anodes, and many gearcase seals are shared between 8HP and 9.8HP variants. Match props by shaft and gear ratio.

MFS9.9 EFI 4‑Stroke (select variants)

Feature	Description
Configuration	Inline-2, SOHC 4-stroke with electronic fuel injection (ECM-controlled); manual or electric start; tiller or remote options.
Common Models	MFS9.9 EFI variants; confirm by model sticker and serial for exact parts.
Advantages	Improved cold starts and throttle response, efficient fuel delivery, and lower emissions.
Notes	Cooling and gearcase components often align with carbureted models; fuel and electrical parts differ (injectors, high-pressure filter, ECM).

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the service schedule and procedures in your official Tohatsu service manual.

Item	Interval*	Remarks	Parts Link
Engine oil & filter	Initial 20 hrs, then every 100 hrs or annually	Use marine 4-stroke oil to spec; replace the oil filter at each service.	Oil Filters
Gear oil (lower unit)	Every 100 hrs or annually	Check for water/milkiness; replace crush washers; reseal if contamination is found.	Tohatsu Lower Unit Seal Kits
Spark plugs	Inspect 100 hrs; replace 200 hrs or as needed	Gap to spec; replace sooner if fouled from rich running or storage issues.	Spark Plug
Fuel filter / inline filter	Every 100 hrs or annually	Replace more often with ethanol fuel or dirty tanks; verify flow direction.	Fuel Filters
Water pump impeller / kit	Every 2–3 seasons or 200 hrs	Replace sooner if weak telltale or overheat; renew housing if scored.	Tohatsu Water Pump Repair Kits
Anodes (internal & external)	Inspect 50 hrs; replace when 50% consumed	Choose zinc (saltwater) or aluminum/magnesium per environment; ensure tight, clean contact.	Anodes
Propeller & cotter/lock hardware	Inspect each trip; service annually	Check for dings and proper pitch; grease splines; carry a spare cotter pin.	Propellers
Thermostat	Inspect annually; replace ~2 years	Stuck thermostats cause cold running or overheat; replace gasket when servicing.	Tohatsu Outboard Parts

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 / overheat alarm	Inspect intake screens for debris, verify thermostat operation, and check impeller condition; confirm good hose pressure on muffs.	Water pump kit, thermostat, intake screen, anodes
Hard starting / rough idle	Prime bulb firm, fresh fuel, clean plugs; carb models: choke/enrichment and idle mixture; EFI models: battery voltage and injector/fuel filter condition.	Spark plugs, fuel filter, carburetor kit, injector/filter (EFI)
Poor acceleration / power loss	Prop damage or wrong pitch, compression check, restricted fuel flow, misfire, or partially clogged jets/injectors.	Propeller, fuel filter, carburetor kit or injector service, ignition coils
Gearcase noise / metal in gear oil	Check for water intrusion, inspect drain plug seals, evaluate shaft/bearing play; reseal if needed.	Lower unit seal kit, bearings, drain plug gaskets
Weak charging (electric-start models)	Test battery and connections, inspect rectifier/regulator wiring, verify stator output.	Rectifier/regulator, stator, battery cables

FAQs

Are parts interchangeable between 8HP, 9.8HP, and 9.9HP models?

Many wear items (water pump components, anodes, several gearcase seals) interchange between 8HP and 9.8HP carbureted platforms. EFI 9.9HP models share numerous mechanical parts but differ in fuel and electrical components. Always verify by model code, serial, and configuration.

When should I replace the water pump impeller?

For typical recreational use, replace the impeller every 2–3 seasons (about 200 hours) or sooner if the telltale weakens, overheating occurs, or you strike sand/debris. Consider a full pump kit if the wear plate or cup is scored.

How often should I change the gear oil?

Change the gear oil every 100 hours or annually. Inspect for water (milky color) or metal on the magnet. If contamination is present, replace drain plug gaskets and perform a pressure/vacuum test; reseal with a lower unit seal kit if needed.

What information do you need to confirm part compatibility?

Provide the full model code (e.g., MFS8/MFS9.8/MFS9.9 with suffix), serial number, shaft length (S/L/XL), starting/control type (manual/electric; tiller/remote), and a photo of the nameplate and the part you’re replacing.

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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.