Tohatsu 4-Stroke 15-20HP Outboard Engine Parts

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This page is tailored for Tohatsu 4‑Stroke 15–20HP outboard engines. Use it to find compatible parts and practical service information, including maintenance tips, common replacement items, and troubleshooting guidance. You can also browse the main Tohatsu collection any time. Scroll to the bottom of this page to start browsing parts specific to this engine, and remember you can 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 15–20HP Model

Locate the identification plate: typically on the transom bracket or clamp bracket. Note the model, serial number, and any suffix letters.
Read the model code: for 4‑stroke models, codes like MFS15/MFS20 are common. Suffixes often indicate shaft length (S/L/XL) and control type (tiller/remote).
Year/version cues: early‑2000s units are commonly carbureted; later versions may feature updated ignition/fuel systems. Match parts to your exact serial range.
Shared platforms: many 15–20HP 4‑stroke twins share cooling, ignition, and gearcase service parts across close HP ratings, but verify by serial and suffix before ordering.

Engine Overview

Tohatsu 4‑Stroke 15–20HP Platform

Feature	Description
Configuration	Twin‑cylinder SOHC 4‑stroke; early 2000s models commonly carbureted with conventional CDI ignition. Later variants may include incremental updates to induction and electronics.
Common Models	MFS15, MFS18 (select years), MFS20 and related suffixes for shaft length/control type.
Advantages	Quiet operation, strong fuel economy, simple routine service, and broad parts availability.
Notes	Many cooling system, ignition, and gearcase components interchange across 15–20HP models. Verify starter, carburetor/induction, and gasket revisions by serial/year.

Routine Maintenance & Service Parts

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

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Every 100 hours or annually	Warm the engine before draining; replace crush washer if applicable.	Oil Filters
Gear oil (lower unit)	Every 100 hours or annually	Check for water intrusion or metal particles when draining.	Tohatsu Lower Unit Seal Kits
Spark plugs	Inspect every 100 hours; replace as needed	Replace if fouled, worn, or out of spec; set correct gap.	Spark Plugs
Fuel filter / inline filter	Every 100 hours or annually	Replace more frequently if fuel contamination or storage issues are suspected.	Fuel Filters
Water pump impeller / kit	Every 2–3 seasons or 200 hours	Replace sooner if weak tell‑tale or any overheating occurs.	Tohatsu Water Pump Repair Kits
Anodes (sacrificial)	Inspect every 50 hours; replace when 50% consumed	Use the correct material for your waters (aluminum, zinc, or magnesium).	Anodes

Frequently Used Parts Categories

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

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak tell‑tale stream / overheat alarm	Inspect intake screen for blockage; verify impeller condition; confirm thermostat operation.	Water pump kit, intake screen, thermostat, gaskets
Poor acceleration or power loss	Check prop for damage or wrong pitch; inspect fuel filter and lines; verify spark plug condition and carburetor cleanliness.	Propeller, fuel filter, fuel pump, spark plugs, carburetor kit
Hard starting / rough idle	Confirm fresh fuel; inspect plugs and plug caps; check for vacuum leaks; clean idle circuits and adjust idle speed per spec.	Spark plugs, carburetor parts, fuel lines, clamps
No‑crank or slow‑crank (electric start models)	Test battery voltage and connections; inspect starter relay; check starter motor engagement.	Starter motor, solenoid/relay, battery cables
Gearcase noise / metal in gear oil	Drain and inspect oil; check prop shaft for fishing line; pressure/vacuum test seals if water intrusion is found.	Lower unit seal kit, gear lube, propeller hardware

FAQs

Are parts interchangeable between different years or between 15HP and 20HP models?

Many service parts (cooling, ignition, gearcase seals) interchange across close serial ranges of MFS15/MFS20 4‑stroke engines. However, items like carburetors, starters, and gaskets can change by year or suffix. Always confirm by model, serial, and configuration.

When should I replace the water pump impeller?

As a preventative measure, replace the impeller every 2–3 seasons or about 200 hours. Replace immediately if you see weak tell‑tale flow or any overheating symptoms.

How often should I change the lower unit gear oil?

Change gear oil every 100 hours or annually. Inspect for milkiness (water) or metal particles; either indicates further diagnostic work such as a seal test.

What information do you need to confirm part compatibility?

Provide the full model code, serial number, shaft length, control type (tiller/remote), and any known year range. Photos of the nameplate and the part needing replacement are very helpful.

Ready to find parts by horsepower, year, and model? Browse the main Tohatsu collection to locate compatible components for your 15–20HP 4‑stroke.

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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.