Mercury Mercruiser 4-Stroke 320HP Marine Engine Parts

(3 products)

This page is for Mercury MerCruiser 4‑Stroke 320HP sterndrive engines. Use it to find compatible parts and service information, including 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 results by horsepower, year range, and part category.

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How to Identify Your 320HP Model

Locate serial tags: engine serial is typically on a decal near the throttle body/ECM or starboard side of the block; the drive (Alpha/Bravo) serial is on the transom assembly/drive housing.
Model wording: common 320HP variants include V8 platforms such as 377 MAG MPI (earlier) or 6.2L ECT (newer, with catalyst). The model label often lists displacement, emission family, and drive pairing.
Drive identification: Alpha models pair with lower outputs; most 320HP engines are matched to Bravo One/Two/Three drives. Confirm your exact drive to ensure propeller, anode, and seal compatibility.
Cooling type: raw-water vs. closed-cooling (heat exchanger). Thermostats, anodes, pump style, and some hoses differ—verify your cooling configuration before ordering.

Engine Platform Overview

V8 377 MAG MPI (320 HP)

Feature	Description
Configuration	V8, multi-port fuel injection 4‑stroke, often paired with Bravo drives
Common Models	377 MAG MPI 320; Bravo One/Two/Three applications
Advantages	Strong mid‑range torque, proven EFI reliability, broad parts availability
Notes	Verify raw‑water vs. closed‑cooling, and drive type for anodes, impellers, and prop fitment

V8 6.2L ECT (320 HP)

Feature	Description
Configuration	V8, EFI 4‑stroke with Emissions Control Technology (catalyst), typically with Bravo drives
Common Models	6.2L 320 ECT; Bravo One/Two/Three variations
Advantages	Improved fuel economy, cleaner emissions, refined calibration and diagnostics
Notes	Many service parts interchange with earlier V8s, but emissions and cooling components may differ—confirm by serial

Routine Maintenance & Service Parts

Intervals below are general guidelines for recreational use; always follow the official MerCruiser service manual for your exact model and duty cycle.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	100 hours or annually	Warm engine before draining; use marine‑rated oil and replace crush seals as required	MerCruiser Oil Filters
Drive gear oil (Alpha/Bravo)	100 hours or annually	Inspect for water intrusion and metal; pressure test if contamination is found	MerCruiser Service & Maintenance Kits
Spark plugs	300 hours or 3 years	Check gap and heat range; replace earlier if fouling occurs	Spark Plug
Fuel filter / water separator	100 hours or annually	Drain and inspect for water; replace element and bowl seals	MerCruiser Fuel Filters
Sea water pump impeller	2–3 seasons or 200 hours	Shorten interval for high‑silt, sandy, or brackish use	MerCruiser Impellers
Anodes (engine/drive)	Inspect every 3 months; replace at ~50% loss	Match alloy (zinc/aluminum/magnesium) to your water type	MerCruiser Anodes
Serpentine/accessory belt	Inspect each season; replace on wear/noise	Verify routing and tension after replacement	Belt
Gearcase seals (pressure test)	Test if water or excessive metal is found	Check prop shaft for fishing line; renew seals and O‑rings as needed	Lower Unit Seal Kits

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Overheat alarm / high temperature	Inspect sea strainer and drive water inlets for blockage; verify impeller condition; test thermostat	Water pump impeller kit, thermostat, intake screens, anodes
Poor acceleration or power loss	Check fuel quality and filter restriction; inspect prop for damage/ventilation; verify throttle linkage	Fuel filter/water separator, fuel pump, propeller
Hard starting / rough idle	Confirm battery voltage and connections; inspect spark plugs; look for vacuum leaks and fouled fuel	Spark plugs, starter, fuel filter
Gearcase noise or metal in gear oil	Check gear oil level/condition; inspect for fishing line at prop shaft; pressure test drive	Lower unit seal kit, prop shaft seals, gear lube
Battery not charging	Verify belt condition/tension; test alternator output and wiring; inspect grounds	Alternator, serpentine belt, electrical connectors

FAQs

Are parts interchangeable between 377 MAG MPI and 6.2L ECT platforms?

Many routine service parts are similar, but emissions, cooling, and some sensors/hoses differ. Always confirm by engine serial number and drive model to ensure proper fit.

When should I replace the raw‑water impeller?

Inspect annually and replace every 2–3 seasons (or ~200 hours), sooner for sandy/silty or high‑temperature operation. Any overheating event warrants immediate inspection.

How often should I change the drive gear oil?

For most recreational use, change every 100 hours or annually. If you find water or metal debris, pressure test and service seals before returning to service.

What information helps confirm part compatibility?

Engine serial number, model designation (e.g., 377 MAG MPI or 6.2L ECT), drive type (Bravo 1/2/3), cooling type (raw vs. closed), and any emissions labels. Photos of the serial tag are very helpful.

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