How to Drop the Lower Unit on a Mercruiser Alpha One Generation Two

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Many maintenance projects on Mercruiser Alpha One, Generation II stern drives begin with removing the outdrive from the back of the boat. Because it's a simple job and can be done quickly, some people remove their units when they put their boats in storage to prevent thieves from stripping the outdrives when the storage area is a less-than-perfectly secure location.

Items you will need

  • Ratchet-wrench with 5/8-inch socket

  • Flat screwdriver

  • Punch

  • Hammer

  • 1/4-inch rope, 10 feet

Unhook the Trim Cylinders

Use the boat's trim and tilt system to put the outdrive in the fully down, vertical position.

Pry off one of the plastic end caps on the end of the shaft which connects the trim/tilt cylinder to the outdrive using a flat screwdriver.

Position the screwdriver under the E-clip, now exposed on the end of the shaft that connects the trim/tilt cylinder to the outdrive. Rotate the screwdriver to begin prying the E-clip loose.

Remove the E-clip with your fingers once it is loose.

Wiggle the lower unit up and down with one hand while attempting to pull the shaft that connects the trim/tilt cylinder to the outdrive out of the cylinder ends and outdrive housing. If it's too tight to remove by hand, put a punch on the end of the shaft and tap firmly enough to push it free.

Tie a length of 1/4-inch rope through the ends of each trim and tilt cylinder. Pull the cylinders upward as far as possible, securing the opposite end of the rope on or inside the boat, holding the cylinders up out of the way.

Remove the Outdrive

Put the boat's gearshift lever into forward gear.

Look on the forward part of the outdrive, just under and between the gimbals that allow the outdrive to tilt for a thin, rubber hose from the boat, attached to a white, nylon fitting on the outdrive. This is the speedometer hook-up.

Remove the speedometer hose from the nylon fitting. This can usually be done with your fingers by pulling upward on the hose.

Use a 5/8-inch socket and ratchet wrench to remove the six self-locking nuts and the flat washers behind them from the studs that connect the lower unit to the back of the boat.

Grasp the lower unit securely with both hands and pull straight back on it. The unit will slide off the studs and the splined shaft on the drive shaft that connects the lower unit to the motor will slide out of the coupler.


  • A lower unit is heavy and cumbersome to handle. If you don't want to have to manhandle it, suspend a rope or ratchet strap from a sturdy rafter or other overhead support directly above the unit and attach it to the end of the rope at the attachment point built into the top of the housing.