Mercruiser Alpha One Application Guide

1. Replaces most Mercruiser Sterndrives from 120-260 HP 1967-1990

2. Your Mercruiser Sterndrive must have trim and tilt to be able to use our aftermarket replacement drive.

3. If your Mercruiser Sterndrive is between 1967-1969 you must verify that you have 13 splines on your upper drive shaft

4. Our Complete Alpha One Gen 1 / Gen 2 Drives ships in 2 boxes (upper / lower).

5. Does not include Complete Install kit or Anode Kit. Please see related items in our shop.

6. To Determine if you have a counter rotation unit on your twin engine boat, it is easiest to look at the props. If the props are same, they are both standard. If the prop blades are opposite, then the port should be a counter rotation.

7. Please Refer to the model chart below to find your proper Mercruiser Sterndrive Replacement.

These are typical applications, it is best to confirm your ratio by counting the teeth in the upper, Although great care was taken in creation of this guide, MercAftermarkets cannot guarantee it's accuracy.


1. Unit has an 8 Spline Driveshaft on the lower unit, if your unit is original, you need to purchase a complete.

2. Unit has a short yoke on the upper driveshaft. We refer to this as the "old style"

3. Unit must have trim and tilt for our Replacement to work.

4. Unit has an eyelet on top cover. Replacement will not work.

5. Unit has a round cavitation plate on the lower unit. Replacement will not work.

6. Unit may have an O-Ring and / Or a preload pin on the lower unit driveshaft. The replacement will not work.

7. Gear ratio must be confirmed. Chart below is typical applications, however there is no guarantee it is correct. To be safe, it is best to count the teeth on the upper gears.


**This ratio is unavailable in the aftermarket application, you can substitute a 1.47 ratio for the 1.32, but it is not covered under the standard warranty.**