Hi David, On my M15 I had the original fixed mount and a short shaft 2 HP HONDA engine when I bought it. You can tilt the motor and it will lock in the tilt position. However, to do that you can't just pull the motor straight back. Then the motor shroud hits the transom, and it won't tilt far enough for the latch to function. You have to turn the motor sideways - if I remember correctly - I turned mine counterclockwise, and then tilted it till the latch locked it in place. Never had a problem doing that. Connie M15 #400