Mercury MerCruiser 6.2L 377 CID 4-Stroke Marine Engine

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This page is for Mercury MerCruiser 4‑Stroke 6.2L (377 CID) sterndrive engines in the 300–350 HP range. Use it to find compatible parts and key service information. Inside you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main MerCruiser collection. Scroll to the bottom of the 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 6.2L (300–350 HP) Model

Locate the serial/ID label: commonly on the starboard side of the engine near the flywheel housing, on the ECM bracket, or on the transom assembly. The serial number is the most reliable way to confirm part compatibility.
Model designation: look for 6.2L ECT 300 or 6.2L ECT 350 along with control type (Mechanical vs. DTS), emissions tag (ECT), and any SeaCore fresh‑water‑cooling package notation.
Drive pairing: many 6.2L engines are matched with Bravo One/Two/Three drives. Knowing the exact drive model and gear ratio helps with propeller and gearcase‑related parts.
Platform clues: both 300 and 350 are 6.2L V8 pushrod EFI engines; differences are typically calibration and accessories (e.g., alternator output, DTS vs. mechanical controls).

Engine Overview

MerCruiser 6.2L 300 ECT V8

Feature	Description
Configuration	6.2L (377 CID) V8, pushrod, 2‑valve/cyl, MPI EFI; typical WOT range ~5000–5400 RPM.
Common Models	6.2L 300 ECT paired with Bravo One/Two/Three sterndrives; SmartCraft engine management.
Advantages	Strong low‑to‑mid torque, smooth planing, broad parts availability, straightforward routine service.
Notes	Uses NMMA FC‑W 25W‑40 oil; supports up to 10% ethanol fuel; fresh‑water cooling available on certain packages. Verify by serial number for exact parts.

MerCruiser 6.2L 350 ECT V8

Feature	Description
Configuration	6.2L (377 CID) V8, pushrod, MPI EFI with SmartCraft; typical WOT range ~5000–5400 RPM.
Common Models	6.2L 350 ECT with Bravo One/Two/Three; often available with DTS controls and optional SeaCore FWC.
Advantages	Higher output calibration, excellent acceleration, compatible with a wide range of Bravo props.
Notes	Check alternator output, control type (DTS vs. mechanical), and cooling configuration when selecting parts. Always confirm via engine serial.

Routine Maintenance & Service Parts

Intervals below are general guidelines for typical recreational use. Always follow the official MerCruiser service manual for your exact engine and drive.

Item	Interval*	Remarks	Parts Link
Engine oil + filter	Every 100 hours or annually	Use NMMA FC‑W 25W‑40; warm engine before draining; replace filter each service.	MerCruiser Oil Filters
Gear oil (Bravo drive)	Every 100 hours or annually	Inspect for water intrusion and metal; change more often for heavy duty use.	MerCruiser Service & Maintenance Kits
Spark plugs	Inspect 100 hours; replace ~300 hours or as needed	Check gap and condition; misfire or hard‑start often traces to worn plugs.	Spark Plugs
Fuel filter / water separator	Every 100 hours or annually	Drain or replace sooner if water or debris is present; ethanol fuel may require shorter intervals.	MerCruiser Fuel Filters
Sea water pump impeller	Every 2–3 seasons (or 200–300 hours)	Replace more frequently in sandy/silty water or if overheat occurred.	MerCruiser Impellers
Corrosion anodes	Inspect monthly; replace when ~50% consumed	Match anode material to water type (zinc/brackish, aluminum/salt, magnesium/fresh).	MerCruiser Anodes
Drive bellows inspection	Check annually; replace ~2–3 years	Look for cracking or leaks to prevent water ingress to U‑joints and gimbal bearing.	Bellows

Frequently Used Parts Categories

Routine Service Kits – MerCruiser Service & Maintenance Kits
Cooling System – MerCruiser Impellers
Fuel System (Filters) – MerCruiser Fuel Filters
Fuel System (Pumps/Injectors) – Fuel Pumps • Injectors
Ignition / Electrical – MerCruiser Alternators • Starters • Sensors
Corrosion Protection – MerCruiser Anodes
Gaskets & Propulsion – MerCruiser Gaskets • MerCruiser Propellers

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Overheat alarm / high temperature	Inspect sea water pick‑ups on the drive, strainer (if equipped), pump impeller, hoses, and thermostat.	water pump impeller, sea water pump kit, thermostat, hoses, gaskets, anodes
Poor acceleration / can’t reach WOT	Check prop pitch/condition and hub, fuel quality, fuel filter restriction, and spark plug condition.	propeller, fuel filter, spark plugs, fuel pump, injectors
Hard starting / rough idle	Look for stale fuel or water in separator, vacuum leaks, dirty injectors, sensor faults (MAP/IAT/IAC).	fuel filter, injectors, sensors, spark plugs
Gearcase noise / metal in gear oil	Verify gear lube level/condition; check for water intrusion and prop shaft seal damage.	lower unit seal kit, bearings, gear lube, prop hardware
Low charging voltage / battery warning	Inspect belt tension/condition, alternator output, and wiring/grounds.	alternator, belt, tensioner pulley, electrical connectors

FAQs

Are parts interchangeable between the 6.2L 300 and 350 ECT engines?

Many service parts are shared across the 6.2L family, but calibrations, control type (DTS vs. mechanical), alternator output, and cooling options can differ. Always confirm with your engine serial number to ensure a correct fit.

When should I replace the sea water pump impeller?

As a general rule, every 2–3 seasons (or 200–300 hours). Replace sooner if operating in sandy/silty water, if the engine overheated, or if impeller vanes show set or cracking.

How often should I change the gear oil in my Bravo drive?

Typically every 100 hours or annually. Inspect more frequently for water intrusion or heavy use, and always service after any prop strike or evidence of metal in the oil.

What information do you need to confirm part compatibility?

Provide the engine serial number, model (e.g., 6.2L 300 or 350 ECT), control type (DTS or mechanical), drive model (Bravo I/II/III) and, if known, gear ratio. Photos of the serial label and the part you’re replacing also help.

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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.