Recently purchased a 1983 30 hp mariner that doesn't engage in reverse. It sounds like it tries but doesn't fully engage. Are there adjustments on the shifter, cables or LU to fix this?
I managed to make some improvement in my shifting problem. After I replaced the impeller I found the shifting rod was connected by a connection nut that was adjustable from outside the lower unit. I separated the lower shift rod from the upper one and force the lower rod down about an eighth of an inch then re joined the two rods. now it shifts into reverse just fine.
Great. Also most Merc reverse gear engagement points are squared off, not saw toothed like F gear. As a result, before you put the shifter in R, you need to rotate the prop as you slowly move the shifter and when the cogs line up it will easily fully go into gear. Otherwise you could bend your shifter linkage trying to force it.