Mercury – Quicksilver 821307A2 Water Pump Base Kit | Mercury 25–50HP Outboards | 821307A2

Overview

When your outboard’s cooling system starts losing pressure or leaking at the base, this is the fix. The Quicksilver 821307A2 Water Pump Base Kit restores proper sealing and flow in Mercury 25–50HP outboards, keeping your engine running at the right temperature.

Made from reinforced nylon with an integrated seal, this OEM base is built for strength, heat resistance, and a perfect fit. It’s a direct replacement for a wide range of Mercury models, from 25HP carbs to 50HP BigFoot and Jet versions — keeping your cooling system tight and efficient.

Key Features

• Purpose: Replaces a worn water pump base to restore full cooling performance and prevent leaks.
• Fitment: Fits Mercury 25HP carb (0G590000–1B344298), 30/40HP 2-cylinder (0G055314 & up), 30HP carb 3-cylinder (0G760300–1B226999), 30HP EFI 3-cylinder (0T409000–1B226999), 30HP Jet 3-cylinder (0G590000–0T408999), 40HP 3-cylinder (0G590000–1B209735), 40/50HP (1998–1999; 0E288000–0E369299), 40HP carb (0G231123–1B344306), 40HP EFI 3-cylinder (0T409000–1B355027), 45/50HP carb, 50HP BigFoot carb (0G231123–0T178499), and 50HP 3-cylinder (0G590000–0T979999; 1B000001 & up).
• Construction: Made from reinforced nylon with an integrated seal for durability and tight fitment.
• Contents: Includes water pump base and O-ring.
• OEM Quality: Built to Mercury Marine factory standards for long-lasting reliability.

Engine & Boat Compatibility

• Mercury 25–50HP carbureted, EFI, and Jet outboards
• Common on small fishing boats, pontoons, and light-duty runabouts

Performance & Practical Benefits

The 821307A2 base kit restores the solid foundation your water pump needs for proper pressure and cooling flow. A worn base can cause water leaks or low flow, leading to overheating and reduced engine life.

The reinforced nylon material holds up to heat, pressure, and vibration without cracking or warping. With the included O-ring and seal, you’ll get a tight, leak-free fit that keeps your cooling system efficient and reliable for years.

Why Buy OEM

Mercury’s OEM components are made to exact tolerances — every piece fits precisely and lasts longer under marine conditions. Aftermarket parts often use lower-grade plastics or seals that can deform, leading to leaks or premature failure.

A genuine Quicksilver base kit ensures you’re using parts tested by the same engineers who designed your outboard’s cooling system. It’s a perfect fit and long-term peace of mind.

FAQ

Q1: What engines fit the Quicksilver 821307A2 kit?
A: It fits Mercury 25–50HP carbureted, EFI, and Jet outboards, including the serial ranges listed above.

Q2: What’s included?
A: One reinforced nylon water pump base and O-ring.

Q3: Why replace the water pump base?
A: A worn or cracked base can cause leaks or poor water pressure, leading to cooling issues.

Q4: Can I install it myself?
A: Yes. It’s a direct replacement that installs easily using common tools.

Q5: Why choose OEM over aftermarket?
A: OEM parts ensure perfect sealing, correct material strength, and the durability Mercury engines were built to have.