Gone Outdoors

How Install a Mercruiser Bellow

by Will Charpentier

Installing a Mercruiser's bellows is about tearing down and reassembling part of the sterndrive, not replacing a torn, ratty, plastic bellows between your boat's transom and the drive. The Alpha One, Generation II sterndrive has individual shift, exhaust and universal-joint bellows that live inside the drive and eliminate the need for the external bellows found on other inboard-outboard drives.

1. Take stock of the steps you’ve taken, once you’ve removed the sterndrive from the boat and inventory, and identify, each of the parts you’ve removed. You’ve taken out the two screws, washers and retainers that hold the trim position sensor in place; removed the two screws, washers and retainers that hold the trim limit switch in place; and removed the switch and sensor from the drive. You’ve also unhooked the shift cable from its guide plate; loosened the cable-end anchor screws; removed the cable-end guide; and loosened the jam nuts and removed the threaded shift cable tube.

2. Locate the remaining shift-shaft related parts you removed and the tools you used. You’ve unhooked the safety wire and removed the setscrew from the shift slide, removed the shift wire’s inner core and shift slide. Then you pulled the shift bellows crimp clamp and removed the shift cable wrap from the shift cable, removed the screws that held the water tube cover and the grommet beneath it. After you used the bellows removal tool to tighten – not loosen -- the nut on the U-joint bellows, you pulled the sleeve from the universal-joint bellows, loosened the hose clamp that holds the U-joint bellows and the clamp that holds the exhaust bellows in place on the gimbal housing. You’ve removed the U-joint bellows from its flange, and the exhaust bellows from its flange. Now you have to install the new U-joint, exhaust and shift bellows.

3. Inspect the bellows for damage and replace them, if necessary. Before you reinstall the bellows, remove any adhesive from the U-joint and shift bellows, using a rag soaked in naphtha. Clean the bellows-mounting flanges with a wire brush or sandpaper and remove any loose particles using a naphtha-soaked rag. Install the shift housing bellows on its flange on the gimbal housing, position the bellows clamp on the end of the bellows that fits over the flange and tighten the clamp securely.

4. Remove the grounding clips from the old bellows. Position the grounding clips – Mercruiser part No. 18654 – onto the exhaust bellows and the U-joint bellows. Apply the appropriate Mercruiser bellows adhesive to the mounting surface of the bellows and allow the adhesive to dry for about 10 minutes. Position the bellows on the gimbal housing, install the bellows clamps and torque the clamps’ screws to 40 inch-pounds. Position the other end of both the exhaust and U-joint bellows so the bell housing exhaust flange and the bell housing U-joint flange are in the grooves on the bellows. Lubricate the U-joint bellows sleeve with engine cleaner and drive it into the bellows with a driving rod. Apply adhesive to the inner surface of both bellows at the bell housing end, position the grounding clips into the bellows and place the hose clamps over the ends of both bellows.

5. Insert the shift cable through the shift cable bellows. Wrap the shift cable with the cable wrapping you removed so the end of the wrapping is about two inches from the gimbal housing. Install the cable’s core wire in the shift slide and the core wire through the shift cable. Allow the bellows to collapse to two and a half inches from the bell housing and install the crimp clamp to hold the bellows to the cable. Reinstall the setscrew into the shift slide and tighten it until it makes contact with the wire, then back it off about one-eighth turn. Using a figure-eight pattern, secure the setscrew to the shift slide with safety wire and bend the tail of the wire between the screw and the tab on the slide. Cut off any excess safety wire.

6. Replace the water tube cover’s grommet and replace the water tube cover. Reinstall the threaded tube onto the shift cable and tighten its jam nut until finger-tight. Push the shift cable core while turning the propeller clockwise, until it stops. Install the shift cable guide on the cable and push the core wire through the cable anchor. Measure the distance between the center of the hole in the shift cable-end guide and the center of the brass barrel with a tape measure; it should be six inches. Connect the shift cable to the shift plate. Reinstall the trim limit switch and the trim position sensor.

Items you will need
  • Standard flat-blade screwdriver
  • Mercruiser bellows removal tool
  • Rags
  • Naphtha
  • Grounding clips, Mercruiser part No. 18654
  • Driving rod
  • Mercruiser bellows adhesive
  • Torque driver
  • Roll of safety wire
  • Measuring tape
  • Propeller nut wrench


  • You can install a Mercruiser's bellows without removing the sterndrive from the boat, but you should do so only if you have no alternative. If you must do so, it's best to pull the boat into an enclosed or covered area, to prevent damage to the drive.


  • Before you work on your boat’s engine or sterndrive, or before you remove the sterndrive from the engine, remove the propeller nut with a propeller wrench. Slide the thrust hub, propeller and washers from the propeller shaft. Failure to remove a propeller before working on an engine that’s out of the water is an invitation to a propeller-strike injury, which can maim or kill.


  • Mercury Mercruiser Service Manual Number 14: Sterndrive Units, Alpha One - Generation II

About the Author

Photo Credits

  • aarrows/iStock/Getty Images