Greetings and welcome to iBoats.
Have the Moderators move your post to the Mercruiser section, since you are talking about a Bravo 1.
It is not clear if you are having a problem with the shifter/throttle control lever thingy or the outdrive itself. Check your control mechanism and the shift adjustment at the engine (there is a special too for checking/adjusting the shift linkage)
If it turns out to be the outdrive, then there is a common repair item as the cone clutch within the Bravo ages, becomes glazed, and does not engage properly. There is a 'poor man's ' fix and then the prescribed fix, which is to replace the clutch & gear set in the upper portion of the outdrive.
B.T.D.T. and I chose the poor man's approach.