Mercury 4-Stroke Outboard Marine Engine Parts (35-300HP)

(2 products)

This page is for Mercury 4-Stroke 35–300HP outboard engines. It helps you find compatible parts and service information, with maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Mercury collection, and you can scroll to the bottom of this page to start browsing parts for this engine. 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 35–300HP Model

Locate the engine’s identification plate: typically on the transom bracket or swivel bracket; the cowl decal may not provide the full model details.
Record the serial number and model designation. Mercury parts lookups are organized by serial number ranges; suffix letters often indicate shaft length (L/XL), tiller vs. remote, and other options.
Confirm 4‑stroke features: an engine oil fill/cap and oil filter on the powerhead, and “EFI/4‑Stroke/Verado/Pro XS/SeaPro” branding on many models.
Different platforms exist in this range (inline EFI, Verado supercharged, newer V6/V8). Some components are platform‑specific, so match by serial range when possible.

Platform Overview

Inline EFI Platforms (approx. 35–150HP)

Feature	Description
Configuration	EFI 4‑stroke, inline‑3 (35–60HP) and inline‑4 (75–150HP) variants
Common Models	40–60 EFI (3‑cyl), 75/90/115 EFI (4‑cyl), 135/150 EFI (4‑cyl, non‑Verado)
Advantages	Strong fuel economy, simple routine service, broad parts availability
Notes	Select parts by serial number; mid‑series updates can change filters, water pump kits, and gearcase components.

Verado L4/L6 Supercharged (approx. 135–300HP)

Feature	Description
Configuration	Supercharged EFI 4‑stroke, inline‑4 (L4) and inline‑6 (L6) platforms
Common Models	135/150/175 L4 Verado; 200/225/250/300 L6 Verado; Pro Verado variants
Advantages	High output with smooth power delivery; advanced controls and charging systems
Notes	Many parts (intake, cooling, belt drive) are platform‑specific; always confirm by serial number and exact Verado generation.

3.4L V6 and 4.6L V8 (approx. 175–300HP, including SeaPro/Pro XS)

Feature	Description
Configuration	Naturally aspirated EFI 4‑stroke, 3.4L V6 and 4.6L V8 platforms
Common Models	175/200/225 V6; 200/225/250/300 V8; SeaPro and Pro XS variants
Advantages	Excellent mid‑range torque, modern charging and controls, reduced maintenance
Notes	Some parts differ by AMS (Advanced MidSection), gearcase style, and model family; verify by serial range.

Routine Maintenance & Service Parts

Intervals below are general guidelines for Mercury 4‑stroke outboards. Always follow the specific procedures and intervals in your official service manual.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	100 hours or annually	Use NMMA FC‑W oil of the recommended grade; replace filter with every oil change.	Oil Filters
Gear oil (lower unit)	100 hours or annually	Inspect for water intrusion and metal. Replace seals if contamination is found.	Mercury Lower Unit Seal Kits
Spark plugs	100–300 hours (usage dependent)	Check gap and replace if fouled, worn, or at scheduled interval.	Spark Plugs
Fuel filter / water‑separating filter	100 hours or annually	Replace more often with poor fuel quality or storage in humid climates.	Fuel Filters
Water pump impeller / kit	2–3 years or 200 hours	Shorten interval for sandy/silty water or weak telltale stream.	Mercury Water Pump Repair Kits
Anodes (sacrificial)	Inspect every 50 hours; replace when 50% depleted	Match alloy to water type (fresh, brackish, salt). Keep paint off anode surfaces.	Anodes

Frequently Used Parts Categories

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

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak telltale stream / overheat alarm	Inspect intake screens, verify water pump condition, thermostat operation, and debris around the lower unit.	Water pump kit, thermostat, intake screen
Poor acceleration / power loss	Check prop condition/pitch, fuel quality, replace fuel filter, inspect spark plugs, and verify throttle/trim settings.	Propeller, fuel filter, spark plugs
Hard starting / rough idle	Prime fuel system, check for stale fuel, replace plugs, and inspect air/fuel delivery for restrictions.	Spark plugs, fuel filter
Gearcase noise / metal in gear oil	Drain gear oil to inspect for water/metal, check prop shaft seals and fishing line damage, verify gear lash and bearing condition.	Lower unit seal kit, bearings

FAQs

Are parts interchangeable between different years or platforms?

Some service items may cross between years, but platform and serial number changes are common (especially across Inline EFI, Verado, and V6/V8 families). Always confirm by serial number and model family before ordering.

When should the impeller be replaced?

Replace the impeller every 2–3 seasons or about 200 hours, sooner if the telltale is weak, you run in sandy/silty water, or after an overheat event.

How often should gear oil be changed?

Every 100 hours or annually. Inspect for milky oil (water intrusion) or metal; address leaking seals or wear before returning to service.

What information helps confirm part compatibility?

Provide the engine serial number, horsepower, approximate year, and any model family identifiers (e.g., Verado, Pro XS, SeaPro). Photos of the nameplate and the part to be replaced are also helpful.

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

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If you’re unsure about your model, send us a clear photo of the nameplate and the part you need and we’ll help verify compatibility.