Mercury – 300 Hour Maintenance Kit | MerCruiser 4.3L Carbureted Alpha Drive | OEM Service Components | 8M0147063

Overview

If you run a MerCruiser 4.3L carbureted engine, you know exactly what it feels like when that V6 is dialed in just right—smooth throttle, clean exhaust note, and the steady push that lets you relax into a long stretch of open water. The Mercury 8M0147063 300 Hour Maintenance Kit is built for boaters who want to keep that feeling going. Everything in this kit supports the health, efficiency, and reliability of your engine and Alpha sterndrive system, giving you the peace of mind that only a proper, factory-spec service can offer. Whether you’re cruising a quiet lake or running a long coastal channel, this kit helps ensure your engine responds the way it should every time you turn the key.

Key Features

• Complete 300-hour service kit for 4.3L carbureted MerCruiser engines
• Works with engines using direct-to-block oil filter mounting and Alpha sterndrive systems (1996 and newer)
• Includes oil filter, fuel filter, gearcase drain seals, spark plugs, thermostat, thermostat gasket, and serpentine belt
• High-pleat oil and fuel filters capture fine debris for cleaner lubrication and fuel delivery
• Corrosion-resistant housings and materials designed for harsh marine environments

Engine & Boat Compatibility

• Fits MerCruiser 4.3L carbureted engines made by General Motors
• Compatible with Alpha sterndrives from 1996 and newer
• Suitable for bowriders, cuddy cabins, runabouts, ski boats, and light cruisers
• Ideal for both recreational and light commercial applications

Performance & Practical Benefits

A proper 300-hour service is more than just a checklist—it’s a chance to restore the engine to its best self. Clean spark plugs help bring back crisp starts and smooth acceleration. The thermostat and gasket ensure stable temperature control, preventing the swings that can hurt performance over time. The serpentine belt refreshes accessory drive alignment, removing the wobble, slip, or squeal that often sneaks up after a few seasons.

The included oil and fuel filters play the biggest role in long-term health by keeping contaminants out of critical pathways. You’ll notice steadier idle, smoother transitions on and off plane, and more predictable throttle response. And with fresh gearcase drain seals, you protect the sterndrive from water intrusion—one of the biggest threats to gear longevity.

When all these components work together, you get a more confident, more enjoyable ride. Everything feels tighter, cleaner, and more willing.

Why Buy OEM

Mercury designs these kits around the exact specifications of each engine family. That means every part—every seal, filter, and belt—is built to the tolerances your engine was engineered for. Aftermarket substitutions might seem tempting, but they rarely match OEM quality, especially when exposed to saltwater or high-hour use.

With OEM parts, you’ll get better reliability, fewer surprises, and long-term protection for your investment. It’s the smart choice for boaters who would rather spend their weekends out on the water than dealing with unexpected repair bills.

FAQ

Q1: Which engines does this kit fit?

It fits MerCruiser 4.3L carbureted engines (1996 and newer) with oil filters mounted directly to the block and Alpha sterndrives.

Q2: What makes OEM better than aftermarket?

OEM parts match exact engineering specs, ensuring proper filtration, durability, and fit.

Q3: How can I confirm it’s the right kit?

Check that your 4.3L carb engine uses a block-mounted oil filter and an Alpha sterndrive.

Q4: Can it be used in saltwater?

Yes—every component is designed for saltwater and freshwater environments.

Q5: Is installation straightforward?

If you’re comfortable with routine marine maintenance, this kit installs cleanly and predictably.