How to Remove a Johnson Seahorse Water Pump

Removing the water pump on one of Johnson's Seahorse motors takes few tools. Two-thirds of the process involves draining the gear oil and removing the lower unit, and can be accomplished while the motor remains mounted on your boat with the boat resting on its trailer. Once the oil is drained and the lower unit removed from the motor, you can move the lower unit to your workbench and begin the water pump removal.

Place a suitable container under the lower unit. Loosen the oil level/vent plug on the lower unit with a screwdriver and remove the drain/filler plug from the bottom of the lower unit. Allow the lubricant to completely drain from the lower unit.

Unsnap the cover from the starboard side of the exhaust housing to access the shift rod. Remove the shift rod screw. Remove the two bolts, both threaded up into the exhaust housing from underneath the cavitation plate, that secure the lower unit to the exhaust housing, using an adjustable wrench.

Pull straight downward on the lower unit to separate it from the motor, withdrawing the drive shaft from the exhaust housing as you separate the lower unit.

Remove the nuts securing the water pump housing to the lower unit, then lift the housing from the top of the lower unit. Work the impeller up and off the drive shaft. Remove the impeller key.

Remove the impeller plate. Dip a clean cloth in denatured alcohol and clean all traces of gasket from the top of the gear case housing and the bottom of the impeller plate.


  • Disconnect the negative cable of your battery before performing any maintenance work on your outboard motor, to prevent electrical shock or accidental starting. Remove the nut from the negative post with a 5/16-inch box-end wrench. Lift the cable from your battery, move it outside of the battery box and close the lid of the battery box.
  • If you work on your outboard motor when your boat is on its trailer, or your motor is on a storage stand, remove the propeller nut with a wrench and slide the thrust hub, propeller and washers from the propeller shaft. Failure to remove a propeller before operating an outboard out of the water during maintenance or long-term storage is an invitation to a propeller-strike injury, which can maim or kill.


  • "Johnson Repair Manual -- 2.5 to 250 HP Models, 2002-2007"; Seloc Marine; 2007

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.