Mercury – 300 Hour Maintenance Kit | 4.6L V8 SeaPro & Pro XS CMS | Full Service Components | 8M0149931

Overview

There’s something reassuring about knowing your engine is ready for another long season before you even leave the dock. When you fish hard, run long distances, or put real hours on your boat, having a dependable maintenance routine becomes part of the rhythm of boating. The Mercury 300 Hour Maintenance Kit 8M0149931 brings that peace of mind into one neatly organized package. You open the box, look over the parts, and you just know — everything you need to keep your V8 running smooth, cool, and confident is right here. It’s the kind of kit that makes you feel prepared, whether you’re chasing early-morning bait schools or hauling gear back across rough afternoon chop.

Key Features

• Complete 300-hour service kit for Mercury 4.6L V8 SeaPro and Pro XS engines
• Designed for Conventional MidSection (CMS) models with serial number 2B529482 and above
• Includes oil filter, fuel filter, oil drain seal, spark plugs, thermostat, alternator belt, water pump repair kit, and anodes
• Premium internal pleat-count filters for high-efficiency filtration
• Heavy-duty electroplated housings for corrosion resistance
• Engineered to meet strict Mercury Marine OEM standards for reliability

Engine & Boat Compatibility

• Fits Mercury 4.6L V8 SeaPro outboards
• Fits Mercury 4.6L V8 Pro XS outboards
• Compatible with CMS (Conventional MidSection) platforms
• Ideal for high-hour commercial vessels, guide boats, offshore rigs, bay boats, and heavy-use fishing setups

Performance & Practical Benefits

This kit isn’t just a box of parts — it’s a full reset for an engine that works hard. Each component plays its role in bringing back that tight, refined feel you notice right after a service. Fresh filters clear out the restriction that slowly builds over time, letting your engine breathe freely. New spark plugs sharpen throttle response, giving you that crisp ignition snap that makes a V8 sound alive. The thermostat and water pump components help keep temperatures steady, which matters a lot on long runs where even small cooling inconsistencies can add up.

You’ll also appreciate how precise the alternator belt fitment is. A worn belt can squeal, slip, or create tiny fluctuations you may not hear — but you’ll definitely feel them in uneven charging or battery strain. Replacing it during your 300-hour service keeps electrical systems stable and strong.

And those anodes? They’re your quiet guardians, taking the punishment so your engine’s internal metal doesn’t. Swapping them out ensures continued protection, especially if you run in brackish or saltwater environments.

The whole kit installs cleanly because every part is designed for your exact engine. No guesswork, no hunting down mismatched components. Just a solid day of maintenance that rewards you every time you push the throttle forward.

Why Buy OEM

• Mercury builds each part to match your engine’s tolerances exactly
• Reliable long-term protection for high-hour engines
• Filters and seals last longer and perform better than most aftermarket options
• Saves money by preventing premature wear and bigger repair bills
• Everything fits correctly the first time — no frustration, no surprises

If a fellow boater asked which kit to trust, you’d point them to this one. It’s simply the most reliable way to service a hardworking V8.

FAQ

Q1: Which engines does this kit fit?

It fits Mercury 4.6L V8 SeaPro and Pro XS CMS outboards with serial numbers 2B529482 and higher.

Q2: What makes this different from aftermarket service kits?

OEM parts match Mercury’s exact specifications, ensuring tighter fitment, longer life, and dependable performance.

Q3: How do I know this is the correct kit for my engine?

Match your serial number and confirm your motor uses the Conventional MidSection design.

Q4: Can this kit be used for saltwater boats?

Absolutely — the included anodes and corrosion-resistant components are ideal for both saltwater and freshwater use.

Q5: Is installation manageable for most boat owners?

Yes. Anyone familiar with routine outboard service will find the process straightforward, especially with all parts included.