Mercury 8HP 2-Stroke Outboard Motor Parts | Marine Engine Components

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This page is for Mercury 2-Stroke 8HP outboard engines. Use it to find compatible parts and service information, including maintenance tips, frequently replaced items, and troubleshooting guidance. You can also browse the main Mercury 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 8HP Model

Find the serial/nameplate on the transom clamp bracket or swivel bracket; capture the full serial to confirm parts compatibility.
Decode suffixes: S/LS indicate shaft length (Short/Long), manual vs electric start, and tiller vs remote control variants.
This is a 2‑Stroke family; Mercury 8HP of this era often shares architecture with 9.9/15HP models. Carburetor size/jetting and decals distinguish horsepower.
Measure driveshaft housing for shaft length (approx. 15" short, 20" long) before ordering gearcase and water pump components.

Engine/Platform Overview

Mercury 8HP 2‑Stroke Small Twin

Feature	Description
Configuration	Inline 2‑cylinder, carbureted 2‑Stroke with CDI ignition; manual or electric start; 2.00:1 gear ratio typical.
Common Models	8HP 2‑Stroke tiller and remote variants from the early–mid 2000s; shares family with 9.9HP/15HP (many service parts in common).
Advantages	Light weight, simple maintenance, strong low‑speed torque, easy starting when tuned.
Notes	Shaft length (S/L) and control type affect linkages and rigging. Carburetor and jetting are horsepower‑specific; gearcase, water pump, and many ignition items are shared across family.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the official Mercury service manual for your exact serial range and usage conditions.

Item	Interval*	Remarks	Parts Link
Gear oil (lower unit)	Every 100 hrs or annually	Change before storage; inspect for metal or water intrusion. Replace seals if contamination is found.	Mercury Lower Unit Seal Kits
Spark plugs	Inspect 50 hrs; replace ~100 hrs	Use correct heat range and gap; fouling increases with excessive idling or rich mixture.	Spark Plugs
Fuel filter / inline filter	Inspect each 50 hrs; replace yearly	Replace sooner if debris or phase‑separated fuel is suspected; keep water out of the system.	Fuel Filters
Water pump impeller/kit	Every 2–3 seasons or 200 hrs	Critical for cooling. Replace sooner if weak tell‑tale or overheat occurs, or after sandy/silty use.	Mercury Water Pump Repair Kits
Anodes (corrosion protection)	Inspect each season; replace as needed	Use alloy suited to your water (fresh, brackish, salt). Replace when 50% consumed.	Anodes
2‑Stroke oil and fuel mix	Every fill‑up	Use quality TC‑W3 oil and the ratio specified in your manual (commonly 50:1). Verify oil injection service if equipped.	Mercury Outboard Parts
Propeller, hardware, and hub	Inspect seasonally	Check for dings and hub slip; verify nut torque and cotter installation.	Propellers

*Adjust intervals for heavy use, commercial duty, or harsh environments. Always follow your official Mercury service manual.

Frequently Used Parts Categories

Routine Service & Tune‑Up – Mercury Outboard Parts
Cooling System – Mercury Water Pump Repair Kits
Fuel System – Fuel Filters
Ignition / Electrical – Electrical Items
Gearcase & Sealing – Mercury Lower Unit Seal Kits
Propellers – Propellers
Corrosion Protection – Anodes

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak tell‑tale / overheat alarm	Inspect intake screen, water tube seal, and impeller condition; confirm thermostat operation.	Water pump kit, face plate/gaskets, thermostat, intake screen
Hard starting / rough idle	Prime the bulb, verify choke/enrichment, clean carb jets, check plug gap and ignition leads.	Spark plugs, carb repair kit, inline fuel filter, primer bulb/connector
Poor acceleration / power loss	Rule out prop hub slip and fouled prop; verify fuel quality and compression; check timing/throttle linkage sync.	Propeller, fuel pump, carb kit, reed valves, spark plugs
Excessive smoke (2‑Stroke)	Confirm proper mix ratio; ensure choke is not stuck on; check idle mixture setting.	Spark plugs, carb adjustments, fuel/oil management items
Gearcase noise / metal in oil	Drain and inspect gear oil; check prop shaft seal area for fishing line; pressure/vacuum test if contamination present.	Lower unit seal kit, bearings, shims, carrier seals

FAQs

Are parts interchangeable between 8HP, 9.9HP, and 15HP 2‑Stroke models?

Many ignition, cooling, and gearcase parts are shared across the family, but carburetor components, jetting, and some powerhead parts differ by horsepower and serial range. Match by serial/nameplate to confirm.

When should I replace the impeller?

As a preventive measure every 2–3 seasons (about 200 hours) or sooner if the tell‑tale weakens, you ingest sand/silt, or the engine overheats.

How often should lower unit gear oil be changed?

Typically every 100 hours or annually, and always before off‑season storage. Inspect for water intrusion (milky oil) or metal particles; address seals or bearings if contamination is found.

What info do you need to verify part compatibility?

Provide the full serial number, shaft length (short/long), control type (tiller/remote), and starting system (manual/electric). Photos of the nameplate and the part in question are also helpful.

Ready to find parts for your Mercury 8HP 2‑Stroke? Browse the main Mercury collection and use Filter & Sort to narrow by horsepower, year, 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.