Big Water Tube Seal Grommet – Fits Mercury, Mercury Racing, Mariner, and MerCruiser (Replaces Mercury 26-88397, 88397)

Product Details

This Big Water Tube Seal Grommet ensures a critical watertight connection for high-performance marine engines. It is designed for a wide range of Mercury, Mercury Racing, and Mariner 2-stroke outboard models, including performance series from 2.5L Carbureted to the 300 Drag. It also fits select MerCruiser sterndrive systems, such as the Alpha One Gen II.

This part is a direct replacement for Buckshot Racing #77 Big Water Tube Grommet and Mercury part numbers 26-88397 and 88397.

• Installs at both the top and bottom of the water tube, connecting the engine's exhaust plate to the water pump housing.
• Engineered specifically for large-diameter water pump tubes to ensure consistent water flow and prevent leaks at high RPMs.
• Critical for maintaining proper engine temperature in demanding high-performance and racing conditions.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

Mercury / Mercury Racing / Mariner: Fits a variety of 2-stroke high-performance models, primarily from the early 1990s through the late 2000s and newer.

MerCruiser: Compatible with Alpha One Gen II, Speedmaster, Sportmaster, Torquemaster, and Vazer drive systems.

Technical Specs

Product Type

Water Tube Seal Grommet

Fitting Type

Grommet/Seal

Installation

Installed at both the top and bottom of the water tube, connecting the motor water exit at the exhaust plate (top) and the water pump housing (bottom).

Connection

Watertight seal between water pump housing and engine's exhaust plate

Dimensions

13.5" L x 11.0" W x 2.0" H (approx. 34.3 x 27.9 x 5.1 cm)

Weight

0.005 kg (0.01 lb)

Operating Environment

Critical for high-performance applications where engine temperature management is critical at high RPMs.

Design

Designed for large-diameter water pump tubes; Ensures consistent water flow and leak prevention.

What’s in the Box

• 1 x Water Tube Seal (Replaces Mercury 26-88397 / 88397)

Installation Notes

1. Disconnect the negative battery cable for safety.
2. Drain the gearcase lube from the lower unit.
3. Remove the mounting bolts securing the lower unit (gearcase) to the engine midsection.
4. If applicable, disconnect the shift linkage rod.
5. Carefully separate and lower the gearcase from the engine.
6. Locate and remove the old water tube grommets. They are found at the top of the water pump housing and where the tube enters the exhaust plate.
7. Thoroughly clean the grommet seating areas on the water pump and the exhaust plate.
8. Press the new grommets firmly into place, ensuring they are fully seated.
9. Carefully raise the gearcase, aligning the driveshaft, shift shaft, and water tube with their respective connections.
10. Reconnect the shift linkage and securely fasten the lower unit mounting bolts to the manufacturer's recommended torque specifications.
11. Refill the gearcase with fresh marine gear lube.
12. Reconnect the battery cable, start the engine in a safe water environment, and check for proper water circulation and leaks.

Troubleshooting & FAQ

Safety & Important Info

• Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
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