Mercury – Serpentine Belt | Engine Drive System | Rubber Composite | 865615Q03

Overview

There’s a certain peace that comes from running a boat whose engine feels settled and sure of itself. When you turn the key and that V6 or V8 fires up with a steady hum, you know every piece of the system is doing its part. A good serpentine belt doesn’t call attention to itself, but you can feel the difference when it’s the right one—clean, smooth power delivery and no surprises while you’re out enjoying a long afternoon on the water. This Mercury Marine part keeps your engine’s heartbeat steady, no matter if you’re pulling away from the dock or powering through a long stretch of open lake.

Key Features

• Designed for MerCruiser V6 and V8 engines with closed cooling systems
• Built for 2001–2016 Alpha and Bravo configurations
• Measures 2,704mm for precise factory-matched fit
• Crafted from a durable rubber composite designed for marine use
• Matches the original belt installed by MerCruiser
• Engineered for stable tension, clean tracking, and long service life

Engine & Boat Compatibility

• Fits 2001–2016 MerCruiser V6 and V8 (305 and 350 cubic inch) engines
• Works with Alpha sterndrives using closed cooling systems
• Compatible with Bravo sterndrives using standard cooling
• Fits serial numbers 0M320025 through 2A455872
• Common on runabouts, family cruisers, tow boats, and performance-oriented vessels
• Suitable for both sterndrive and inboard configurations using this specific accessory layout

Performance & Practical Benefits

A proper serpentine belt is one of the most underrated performance parts on the boat. It keeps your accessories running with a tight, predictable feel—smooth alternator output, steady circulation from the water pump, and balanced operation across every driven component. When this belt is installed, you’ll notice how the engine settles into a confident rhythm without slipping, squealing, or fluctuating under load.

Because this Mercury Marine part matches the original equipment exactly, the installation process feels natural. The belt lays into each pulley with a clean, even grip, maintaining tension without forcing you to over-tighten or adjust. That perfect alignment helps prevent hot spots and premature wear, while the marine-rated rubber composite holds up against heat, moisture, and vibration. You’ll spend less time thinking about maintenance and more time enjoying the water.

The durability is especially important for engines that see long run times or higher accessory loads. Closed cooling systems benefit from belts that hold their grip consistently, and this one was built with that in mind. Once installed, it becomes one of those parts you trust without thinking twice.

Why Buy OEM

With a serpentine belt, there’s no room for guesswork. The right length, the right groove spacing, and the right material make the difference between dependable operation and a long day of frustration. OEM parts like this one give you the confidence that everything fits and performs exactly the way Mercury intended. You’re not dealing with mystery rubber blends or close-enough sizing. You’re getting the part your engine was designed around, which means better reliability and long-term value. When another boater asks what you’d use on your own engine, this is the belt you’d recommend.

FAQ Section

Q1: Which engines does this belt fit?

It fits MerCruiser 2001–2016 V6 and V8 engines (305 and 350 cubic inch) in the listed serial range.

Q2: How is this better than aftermarket belts?

It’s matched exactly to factory specifications, giving smoother pulley engagement, better tension, and longer life.

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

Check your engine’s serial number, configuration, and cooling system type. If they match the listing, this is the correct belt.

Q4: Can it be used in saltwater and freshwater?

Yes, the belt’s construction is designed for both environments.

Q5: Is installation simple?

Most boaters can install it using basic tools and the routing diagram found in their engine compartment or owner’s manual.