MerCruiser 4-Stroke 325HP Marine Engine Parts

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Parts and guidance for MerCruiser 4-Stroke 325 HP inboard/sterndrive engines. This page helps you identify compatible components, plan service, and solve common issues. You’ll find maintenance tips, frequently replaced parts, and troubleshooting advice below. You can also browse the main MerCruiser collection at any time. Scroll to the bottom to start browsing parts for this engine, and remember you can use the Filter & Sort controls on the collection page to narrow results by horsepower, year range, and part category/section.

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How to Identify Your 325 HP Model

Locate identification plates: the engine serial label is typically on the starboard side of the block or near the flame arrestor; the drive and transom assembly also have separate serial labels.
Model wording often includes displacement and family, for example “5.7L GEN+” or “350 CID,” plus the drive type (Alpha/Bravo) or “MIE” (inboard). These suffixes help confirm parts compatibility.
Confirm fuel and induction type (carb vs. MPI/EFI). Many 300–325 HP small‑block V8 variants share wear items, but ignition, fuel system, and calibration parts can differ.
Record the engine, drive, and transom serial numbers. Having all three ensures accurate selection of cooling, ignition/electrical, and gearcase parts.

Engine Platform Overview

GM Small‑Block V8 5.7L GEN+ (350 CID) – 325 HP

Feature	Description
Configuration	V8 4‑Stroke, 5.7L (350 CID) GEN+; typically Bravo/MIE installations; carb or MPI depending on build
Common Models	MerCruiser 350 5.7L GEN+ Bravo/MIE 325 HP; related 300–350 HP small‑block variants share many service parts
Advantages	Strong mid‑range torque, broad aftermarket support, straightforward seasonal service
Notes	Cooling uses a belt‑driven seawater pump (impeller). Verify drive type (Alpha vs. Bravo) for gearcase and transom components. Always match parts to your serial numbers.

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 marine‑rated oil; replace filter each change	MerCruiser Oil Filters
Gear oil (sterndrive)	Every 100 hours or annually	Change before winter; inspect for water or metal	Mercruiser Service & Maintenance Kits
Spark plugs	Inspect 100 hours; replace 200 hours	Match heat range/type to your serial and induction	Spark plug
Fuel filter / water separator	Every 100 hours or annually	Replace more often in high‑contamination environments	MerCruiser Fuel Filters
Seawater pump impeller	Every 200 hours or 2 seasons	Critical for cooling; replace sooner if flow is weak	MerCruiser Impellers
Anodes (engine/drive)	Inspect every 50 hours; replace when 50% worn	Match alloy to water type (zinc/aluminum/magnesium)	MerCruiser Anodes
Thermostat	Inspect 2 seasons; replace as needed	Replace if running cool/hot or after overheat event	MerCruiser
Gearcase seals (if milky gear oil)	As needed	Pressure/vacuum test drive; renew seals if leaking	Lower Unit Seal Kits
Belts (serpentine/V‑belt)	Inspect 100 hours; replace 200 hours	Check tensioner and pulleys for noise or wear	Belt

Frequently Used Parts Categories

Routine Service Kits – Mercruiser Service & Maintenance Kits
Cooling System (seawater pump/impellers) – MerCruiser Impellers
Fuel System (filters) – MerCruiser Fuel Filters
Ignition / Electrical – MerCruiser Alternators
Propellers & Hardware – MerCruiser Propellers
Gaskets & Seals – MerCruiser Gaskets
Corrosion Protection – MerCruiser Anodes

Common Symptoms & Quick Checks

Symptom	Check First	Related Parts
Overheat alarm / high engine temperature	Seacock open and strainer clear; inspect seawater pump impeller and belt; verify thermostat operation	Seawater pump impeller/kit, thermostat, intake screen/hoses
Poor acceleration / power loss	Propeller condition/pitch; fuel quality and filters; plug condition; throttle and timing per spec	Fuel filters, spark plugs, propeller, hoses
Hard starting / rough idle	Battery voltage; water in fuel; vacuum leaks; idle air control (MPI) or carb setup	Spark plugs, fuel filter/water separator, gaskets/hoses
Gearcase noise or metal in gear oil	Gear lube level/color; prop shaft for fishing line; U‑joints/gimbal bearing; pressure test seals	Gear oil, lower unit seal kit, propeller hardware
Rapid anode loss / corrosion	Correct anode alloy for water type; bonding continuity; stray current/shore power issues	Anodes, bonding straps, cables

FAQs

Are parts interchangeable between 300 HP and 325 HP small‑block V8 models?

Many routine items (filters, impellers, anodes, belts) interchange across 300–325 HP 5.7L GEN+ variants, but fuel/ignition components and calibration‑specific sensors may differ. Always confirm with your engine, drive, and transom serial numbers.

When should I replace the seawater pump impeller?

A common interval is every 200 hours or two seasons. Replace sooner if the water flow weakens, running temperature creeps up, or after any dry‑run/overheat event.

How often should sterndrive gear oil be changed?

Typically every 100 hours or annually, and always before winter layup. Inspect the drained oil for milkiness (water intrusion) or metal debris and address seal issues promptly.

What information do you need to confirm compatibility?

Provide the engine serial number, drive serial number (Alpha/Bravo), transom assembly serial, horsepower rating, and whether your setup is carbureted or MPI/EFI.

Ready to find parts by horsepower, year, and model? Browse our main MerCruiser collection and use Filter & Sort to zero in on components for your 325 HP setup.

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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.