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MerCruiser 4-Stroke 340HP Marine Engine Parts

(8 products)

This page is for MerCruiser 4-Stroke 340HP outboard engines. Use it to find compatible parts and service information, including maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main MerCruiser 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 340HP Model

  • Serial plate location: Look for the engine serial number tag on the starboard valve cover or near the flame arrestor; the drive unit and transom assembly have separate serial plates.
  • Model code basics: Note fuel system (carbureted vs. EFI/MPI), drive family (Alpha or Bravo), and cooling type (raw-water or closed cooling). These affect gaskets, pumps, and thermostat parts.
  • Platform clues: The 340 HP package is typically a 7.4L (454 CID) 4-stroke V8. EFI engines will have fuel rails and sensors; carb models have a single carburetor and mechanical fuel pump.
  • Record details: Serial number, model designation, and drive ratio help verify propellers, anodes, and service components.

Engine Overview

7.4L V8 (340 HP) Platform

Feature Description
Configuration Gasoline 4-stroke V8, 7.4L displacement; carbureted or EFI/MPI depending on year; typically paired with Alpha or Bravo sterndrives; raw-water or closed cooling.
Common Models 7.4L/454 CID 340 HP packages in carb or EFI variants; common driveline packages include Bravo One/Two/Three.
Advantages High torque for planing heavier boats, broad parts availability, robust cooling components when serviced on schedule.
Notes Parts compatibility varies by carb vs EFI, cooling configuration, and drive family. Use engine and drive serials to confirm impellers, anodes, fuel filters, and gaskets.

Routine Maintenance & Service Parts

Intervals below are general guidelines; always follow your official MerCruiser service manual and adjust for usage and environment.

Item Interval* Remarks Parts Link
Engine oil + filter Every 100 hrs or annually Change more often for heavy loads or frequent idling; warm engine before draining. MerCruiser Oil Filters
Gear oil (drive unit) Every 100 hrs or season-end Check for water intrusion or metal particles; service seals if contamination is present. MerCruiser Collection
Spark plugs 100–200 hrs or annually Inspect gap and insulator color; replace if fouled or out of spec. Spark Plugs
Fuel filter / water separator 50–100 hrs or every season Drain or replace sooner if water or debris is present; use ethanol-safe components. MerCruiser Fuel Filters
Water pump impeller / kit Every 2–3 seasons (or 200–300 hrs) Replace sooner for sand/silt use or any overheat events. MerCruiser Impellers
Anodes (corrosion protection) Inspect monthly; replace when 50% worn Match material to water type (zinc for salt, aluminum for brackish, magnesium for fresh). MerCruiser Anodes

Frequently Used Parts Categories

Common Symptoms & Quick Checks

Symptom Check First Related Parts
Overheat alarm or weak discharge Inspect intake screens/strainer, sea water pump impeller, thermostat, and hose clamps. Water pump kit, thermostat, intake screen, hoses, anodes
Hard starting or rough idle Verify fuel quality, replace fuel/water separator, check spark plugs and vacuum leaks; for EFI, inspect connectors and IAC. Fuel filter, spark plugs, gaskets, sensors/connectors
Poor acceleration or power loss Check propeller damage/pitch, fuel delivery, ignition condition, and throttle linkage. Propeller, fuel pump/filter, spark plugs, ignition components
Gearcase noise or metal in gear oil Confirm proper oil level; look for water intrusion; inspect seals, u-joints, and gimbal bearing. Seals, gear lube, bearings, bellows
Charging warning / low voltage Check belt tension/condition, alternator output, and ground connections. Alternator, belt, battery cables

FAQs

Are parts interchangeable across different years or platforms?

Some service items fit broadly, but many components differ by carb vs. EFI, cooling configuration, and Alpha vs. Bravo drivetrain. Always confirm with engine and drive serial numbers before ordering.

When should the water pump impeller be replaced?

As a rule of thumb, replace every 2–3 seasons (sooner in sandy/silty water or after any overheat). Inspect annually for cracks, set, or missing vanes.

How often should gear oil be changed?

Change every 100 hours or at least once per season, and always before winter storage to prevent corrosion from any moisture in the oil.

What information do you need to confirm part compatibility?

Engine serial number, model designation, fuel system (carb or EFI/MPI), cooling type, and drive family (Alpha/Bravo). Photos of the nameplate and the part you are replacing are also helpful.

Ready to find parts for your MerCruiser by horsepower, year, and model? Browse the main brand collection and use the Filter & Sort controls to narrow your results.

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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.
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