Mercury – Serpentine Belt | Engine Drive System | Rubber Composite | 865615Q04

Overview

There’s something reassuring about hearing your engine settle into that familiar, even rumble when you turn the key. On those mornings when the water’s glassy and the sun’s just clearing the trees, you want every part of your boat working in quiet harmony. A good serpentine belt doesn’t draw attention to itself, but you feel its presence every time your alternator charges cleanly, your cooling system holds steady, and your boat responds with confidence. This Mercury Marine part delivers that sense of reliability, keeping your engine breathing easy whether you’re cruising a calm river or pushing toward open water.

Key Features

• Designed for MerCruiser V6 and V8 engines with standard cooling.
• Built for engines using 305 and 350 cubic inch configurations.
• Measures 1,941mm for precise fit and tension.
• Made from marine-tested rubber composite for long wear.
• Matches the original belt installed by MerCruiser.
• Engineered for smooth tracking and dependable accessory drive performance.

Engine & Boat Compatibility

• Fits MerCruiser 2001 and newer V6 and V8 (305 & 350 cubic inch) Alpha engines.
• Works on engines with standard cooling systems.
• Compatible with serial numbers 0M320025 and above.
• Commonly found on runabouts, bowriders, family cruisers, tow boats, and multi-use recreational vessels.
• Suitable for both sterndrive and inboard setups requiring this specific belt length and routing pattern.

Performance & Practical Benefits

This belt keeps your engine’s vital systems running in a tight, coordinated rhythm. With the correct length and groove profile, the belt grips the pulleys cleanly, reducing slip, vibration, and uneven tensioning. The result is a smooth delivery of power to every accessory—your alternator charges consistently, your water pump circulates steadily, and your steering feels balanced and responsive.

During installation, the difference between an OEM belt and a generic aftermarket one becomes clear. This Mercury Marine part settles into place naturally, matching the factory routing without forcing or stretching. You’ll feel the correct tension the moment it’s seated, giving you confidence that the belt will hold up under long hours of heat, moisture, and engine vibration.

Because it’s built from a marine-specific rubber blend, it resists glazing, cracking, and premature wear—a real advantage if you do long weekend runs or spend time at higher RPM. It’s one of those parts that quietly improves the reliability of your boat without ever being the star of the show.

Why Buy OEM

A serpentine belt may seem simple, but choosing the right one matters. OEM belts are engineered to match the engine’s load requirements, pulley distances, and tension parameters to the millimeter. That means fewer failures, fewer adjustments, and long-term peace of mind. When another boater asks for advice, an OEM belt is the recommendation you give without hesitation. It protects your engine investment and performs exactly the way Mercury intended.

FAQ Section

Q1: Which engines does this serpentine belt fit?

It fits MerCruiser 2001 and newer V6 and V8 (305 and 350 cubic inch) engines with standard cooling.

Q2: Why choose OEM over aftermarket?

OEM belts provide the correct length, groove pattern, and rubber formulation for smooth, reliable operation.

Q3: How do I confirm it’s the correct belt?

Check your engine model, cooling system type, and serial number. If they match the product listing, this is the right belt.

Q4: Is it suitable for both freshwater and saltwater?

Yes, the belt is built with materials that stand up to both environments.

Q5: Is installation difficult?

Most owners can replace it themselves using basic tools and the engine’s routing diagram.