I changed the gears in my Alpha. This what the Mercruiser Instructions said.
Drive Unit 10-Hour Break in Period
1. Avoid full throttle starts.
2. DO NOT operate at any one constant speed for extended periods.
3. DO NOT exceed 75% throttle during the first 5 hours. During the next 5 hours, operate at intermittent full throttle.
4. Drive unit should be shifted into forward gear a minimum of 10 times during break-in, with run-in time at moderate RPM after each shift.