How Do I Drop the Lower Unit on a Yamaha Outboard?

by Will Charpentier

When you drop the lower unit of a Yamaha outboard motor, you're either repairing something or inspecting something. You don't need to do things that will make more work -- take particular care during the procedure, whether in making a "match mark" on the trim tab or just remembering where you put the nuts and washers that hold the lower unit to the rest of the motor.

Open a bench vise to receive the lower unit after you remove it. Pad the jaws of the vise with thick panels of cloth.

Shift the gearcase into "Forward." Make a pencil line that crosses from the trim tab to the cavitation plate to ensure the trim tab is reinstalled at the original angle. Unbolt the trim tab with an open-end wrench and remove it from the motor.

Remove the four bolts, one on the front of the joint between the lower unit and the exhaust housing, one on either side joint between the exhaust housing and the lower unit, and a lock nut and washer beneath the trim tab with a thin-walled socket.

Give the lower unit a sharp tug downward to separate it from the exhaust housing. Ease the the shift rod and driveshaft out of the exhaust housing to avoid damaging or bending them and set the lower unit into the bench vise.

Tighten the bench vise only enough to support the lower unit.

Items you will need

  • Bench vise
  • Thick panels of cloth
  • Pencil
  • Open-end wrench
  • Thin-walled socked

Warning

  • Remember that the driveshaft and the shift rod are attached to the lower unit, not to the powerhead. Both mesh with the motor by use of splines on their shafts; a bent shaft won't mesh exactly when you install the lower unit to the motor again.

References

  • "Yamaha/Mercury/Mariner 4-Stroke Outboards 1995-2004"; 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.