Mercruiser Engine Alignment: Tricks & Tips

There appear only to be a few bits of advice rather than any "tips and tricks" when it comes to aligning the Mercruiser engine, its driveshaft coupler and the propeller shaft of a boat. The first piece of advice is to use the right lifting eye, the second is to use the right engine alignment tool and, finally, use a shop crane to lift and adjust the engine.

  1. You Only Need One Eye and a Crane

    • Use the center lifting eye, located on top of the engine's thermostat housing, to make engine alignment adjustments. Don't use any other lifting eye for the alignment procedure. The shop crane is essential to the process because you have to lift the engine by fractions of an inch, until its coupler splines and the coupler splines at the rear of the transmission fully mesh. This is when you need the Mercruiser engine alignment tool.

    Mercruiser Engine Alignment Tool

    • The engine alignment tool, Mercury Marine part No. 91-805475A1, simplifies your life. The Mercruiser shop manual is specific, saying that other alignment tools "may cause improper alignment and damage to gimbal bearing and/or engine coupler." This tool is designed for Mercruiser engines, and like every other manufacturer, if you don't have its tool, you're likely to sustain damage. While this may seem like a scare tactic, if even the shop manual warns Mercruiser personnel, it's a pretty good bet that using the Quicksilver Alignment Tool is less expensive than the damage you may sustain if you don't use it.

    Quick and Dirty: The Process

    • Try to insert the solid end of the alignment tool through the drive's gimbaled bearing and into the engine's coupler splines. If it doesn't fit in easily, pull it back out. Hook the shop crane to the center lifting eye. Fully loosen the the locknuts found in the channels on the front engine mounts, using a 33 mm socket. Raise or lower the engine in small increments until the alignment tool slides freely all the way in and out of the engine's coupler splines. This may be tedious, exacting work, but it is less expensive than the alternative.

    Final Fit

    • Turn the adjustment nuts, located under the engine mounts, by hand or with a 33 mm open-end wrench. Tighten the locknuts to hold the engine in its proper orientation. Finally, bend the tabs on the adjustment washers down so they jam against the sides of the adjusting nuts.