The Big Water Tube Grommet from Buckshot Racing #77 replaces the Mercury Racing Water Tube Seal (OEM part number 26-88397, also referenced as 88397) an important cooling system component designed to ensure a watertight seal in two (2) places; between (1) the water pump housing and (2) the engine’s exhaust plate in high-performance Mercury, Mercury Racing, and Mariner outboard engines as well as MerCruiser sterndrive systems.
Commonly referred to as the Big Tube, Large Water Pump Seal, or Race Water Tube Seal, this part is essential for maintaining optimal cooling performance in demanding marine environments.
Specifically designed for use with large-diameter water pump tubes, the Mercury 26-88397 seal is 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).
This dual-seal, on both the top and bottom of the water tube, ensures consistent water flow, leak prevention, and system reliability, particularly in Mercury Racing applications where engine temperature management is critical at high RPMs.
This OEM water tube seal is used across a wide range of Mercury Racing and Mariner performance engines, including the 2.5 Liter EFI Offshore, 245 HP Carbureted, 260 EFI, 280 ROS, and the 300 Drag engine.
It is also compatible with Mercury’s high-performance racing lines such as the S3000, S2000, SST-120, SST-200, and the 200 XS Optimax. Additional compatible models include the Mercury 150 Pro Max, 200 Pro Max, and 225 Pro Max, along with their Mariner counterparts: the 150 Super Magnum, 200 Super Mag, and 225 HP Super Mag.
In terms of lower unit and gearcase compatibility, the 26-88397 seal is used in all Speedmaster SSM #4 (IV) gearcases, SSM #6 Big Tube units, Sportmaster, and 2.5L Torquemaster Lower Units. It is also found in the widely used Alpha One Gen II Sterndrive systems.
Whether it’s a closed-deck race boat or offshore fishing vessel, this water tube seal plays a crucial role in supporting engine longevity and performance through effective thermal regulation.
Designed to meet OEM specifications, the Mercury 26-88397 is a direct replacement part that supports the integrity of the marine engine cooling system. A damaged or worn-out water tube seal can lead to water leaks, reduced cooling efficiency, and potential engine overheating—especially in high-output motors.
For boat owners and technicians maintaining Mercury outboard water pumps, MerCruiser cooling systems, or high-performance gearcases, this seal is a must-have for proper service and repair.
Mercury water pump seals, and high-performance outboard cooling system seals like this one are critical to maintaining reliability on the water. When replacing components in a Mercury Racing outboard or Alpha One Gen II Sterndrive, always use genuine parts like the Mercury 26-88397 for maximum durability and fit.
Included one (1) Mercury Big Tube Water Tube Seal Grommet or Buy 3, Save $3 or Buy 10, Save $20 in our Dealer Pack.
Contact Mike Hill with any questions at +1-714-697-1716 or mike@buckshotracing77.com