Mercury MerCruiser 320HP 4-Stroke Marine Engine

(3 products)

This page is for Mercury MerCruiser 320HP 4‑Stroke engines and helps you find compatible parts and key service information. Below you’ll find maintenance tips, commonly replaced items, 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 by horsepower, year range, and part category.

Browse All MerCruiser Parts

How to Identify Your 320HP Model

Locate the serial plate: commonly on the starboard side of the engine or near the bell housing/transom assembly. The sterndrive unit also has an ID tag on the drive.
Read the model code and suffix: codes often indicate displacement/family (e.g., 6.2L), emissions package (ECT/catalyst), and variant. Suffixes can denote specific calibration or drive pairings.
Confirm the platform: 320HP models are typically 6.2L V8 multi‑port fuel‑injected 4‑strokes with SmartCraft electronic control. The WOT range is commonly around 5000–5400 RPM.
Record the drive details: gear ratio and drive model affect propeller choice and some service parts; note both engine and drive serials.

Engine Overview

Feature	Description
Configuration	6.2L V8, EFI/MPI 4‑stroke with SmartCraft electronic management and a high‑output alternator.
Common Models	Examples include Tow Sport 6.2L 320HP variants (e.g., T6200 ECT) paired with MerCruiser sterndrives.
Advantages	Strong mid‑range torque, smooth operation, corrosion‑protection options, and SmartCraft guardian/diagnostics for engine protection.
Notes	Typical WOT range around 5000–5400 RPM; commonly uses NMMA FC‑W 25W‑40 engine oil; regular unleaded fuel (with limited ethanol content) is typical. Verify parts by engine and drive serial numbers.

Routine Maintenance & Service Parts

Intervals below are general guidelines for 4‑stroke V8 sterndrive applications. Always follow the procedures and schedules in your official service manual.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Every 100 hours or annually	Use marine‑rated FC‑W oil (commonly 25W‑40); warm engine before draining for a complete change.	MerCruiser Oil Filters
Drive (gear) oil	Every 100 hours or annually	Check for water intrusion or metallic debris; change more often in harsh use.	MerCruiser Service & Maintenance Kits
Spark plugs	Inspect annually; replace ~300 hours/3 years	Check gap and condition; replace if fouled, worn, or after water ingestion events.	Spark Plug
Fuel/water‑separating filter	Every 100 hours or annually	Drain/replace sooner if water or debris is present; ethanol fuel may require more frequent changes.	MerCruiser Fuel Filters
Sea water pump impeller	Every 2–3 seasons (inspect annually)	Replace sooner if run dry, overheated, or used in sandy/silty water.	MerCruiser Impellers
Anodes (corrosion protection)	Inspect every 50 hours; replace as needed	Use the correct alloy (zinc/aluminum/magnesium) for your water type; ensure good electrical contact.	MerCruiser Anodes
Serpentine/accessory belt	Inspect every 100 hours	Check for cracking, glazing, or noise; tension per spec.	Belt
Thermostat & gaskets	Inspect 2–3 seasons or if cooling issues arise	Replace if running too cool/hot or with scale buildup.	MerCruiser Gaskets

Frequently Used Parts Categories

Routine Service: MerCruiser Service & Maintenance Kits
Oil & Filters: MerCruiser Oil Filters
Cooling System: MerCruiser Impellers
Fuel System: MerCruiser Fuel Filters
Ignition / Electrical: MerCruiser Alternators
Corrosion Protection: MerCruiser Anodes
Propulsion: MerCruiser Propellers

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Weak water flow or overheat alarm	Inspect sea inlet screens, sea strainer (if fitted), impeller condition, and thermostat operation; verify hose clamps and leaks.	Water pump/impeller kit, thermostat, intake screen, hoses, anodes.
Poor acceleration or loss of power	Check propeller damage or incorrect pitch, fuel quality, clogged fuel/water separator, and plug condition; review SmartCraft faults.	Propeller, fuel filter, injectors, spark plugs, fuel pump.
Hard starting or rough idle	Verify battery health/voltage, inspect plugs and leads, check for vacuum leaks, and confirm sensor connections (MAP/IAT/ECT).	Spark plugs, sensors, fuel filter, fuel pump.
Gearcase noise or metal in gear oil	Check oil level and condition; look for water contamination; inspect prop shaft seal area for fishing line.	Lower unit seal kit, bearings, gear lube, prop shaft seals.
Guardian/derate (SmartCraft warning)	Confirm coolant and oil pressure readings, inspect sensor connectors, and resolve stored fault codes before running at high load.	Sensors, oil filter, impeller/thermostat, wiring connectors.

FAQs

Are parts interchangeable between different years or platforms?

Many service items interchange within the 6.2L V8 family, but calibrations, sensors, exhaust components, and drive‑specific parts can vary. Always confirm using both engine and drive serial numbers.

When should the sea water pump impeller be replaced?

Inspect annually and replace about every 2–3 seasons, or sooner if the engine has run dry/overheated or operates in sandy/silty water.

How often should sterndrive gear oil be changed?

Change at least every 100 hours or annually. Replace immediately if the oil appears milky, burnt, or contains metallic debris.

What information helps confirm part compatibility?

Engine serial number, engine family (e.g., 6.2L 320HP), emissions package (catalyst/ECT), sterndrive model and gear ratio, and the boat’s year/model. Photos of the serial plate and the part needing replacement are also helpful.

Ready to find parts by horsepower, year, and model? Browse the main MerCruiser collection for compatible components.

Shop MerCruiser Parts

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.