There may be an issue with your shoert shift cable, the one that goes to the outdrive.
Year of boat, size of motor, some history also....ever overheated?
Here is the shift cable adjustment proceedure.
Alpha 1 shift cable adjustment procedure
Raise outdrive a count of 2-3 seconds from all the way down.
Remove short cable from shift bracket at engine.
Push plastic cable end of short cable all the way IN, have someone turn by hand the prop c’clockwise until full forward engagement.
Measure distance between the center of the brass trunion to the center of the plastic cable end hole that the mounting stud went thru. This measurement must be 6 inches exactly!!
Now shift the control handle to full forward full throttle position.
Try to install short cable onto shift bracket. If it will not fit perfectly, adjust the control shift cable trunion “only” until it does. Once there install short cable back onto shift bracket. Now turn control cable trunion 3-4 turns AWAY from the plastic cable end and install into shift bracket.
Shift control handle to neutral. Prop should spin freely with no clicking sounds.
Now shift back into forward but only to the “detent” aprox, 10:00 oclock . This is when forward gear should be fully engaged. Make sure someone is spinning the prop by hand c’clockwise when doing this.
If you have good forward engagement with no slipping then pull handle back to neutral.
Now shift handle to aprox, 2:00 oclock, have the person spin the prop clockwise. This should give you reverse engagement. If it does then you are done! If it does not and you have a clicking sound/ not full engagement then adjust the short shift cable end where it is mounted, there is a slot, loosen the hex nut under the cable end and move cable towards the end of the arm, say ¼ inch and retry. When full reverse is obtained you are done.
Give this a try and report back with results.
