Thanks for the pics! That's exactly what I have, but I was not comfortable moving the notch outside the groove. And it would definitely need longer screws, as the ones in there are barely long enough with the notch in place.
Before I summarize what I did today, I do want to mention that I discovered that my transmission fluid dipstick has no sealing ring at the top. Does anyone have a suggested replacement that I can find in a brick&mortar auto store? It looks like it would need a fiber washer with ID of 5/8" (16 mm).
I finished removing the compass today and looked down at the chain and linkages. I'm not going to attempt adjusting the linkages there. In addition to the risk of dropping something down the "chimney," those linkages are very long, and you can't just twist them without grabbing the push rods and/or lock nuts. Those elements are buried way too deep to get to. Unless I was seeing it wrong, the only way to adjust would be to remove the cable. I think drilling a new hole in the mounting plate to shift it aft by 1/2" will be a much simpler solution, and fully reversible if I need to put it back the way it is currently.
In looking over things closely, I'm pretty sure this transmission was removed and repainted, presumably as part of a rebuild. There is paperwork from the previous owner indicating that he paid someone to remove it for inspection, but no paperwork that any follow-up work was done. But by the looks of things I'd say it was rebuilt, and I may be about to solve the root cause that led to the rebuild. On the surface this looks like a clear-cut case. The cable only pulls the shift lever into forward by 1" due to binnacle interference, vs. a spec of ~1.2" (for inner holes), but it pushes the lever into reverse by up to 2". So it seems obvious that moving the cable back by 1/2" will make the lever motion symmetrical and well above spec in both directions. Service manual clearly says:
A greater amount of shift lever travel is in no way detrimental and is recommended. However, if the lever travel is shorter, proper clutch engagement might be impeded....This would be indicated by slow clutch engagement or no engagement at all.
...which is exactly what I was experiencing.
I'm pretty excited about this, because it really looks like symptoms and solution line up perfectly. While I wish the PO had fixed this before I took ownership, it's nice to have a clear solution. My pre-purchase surveyor and sea trial captain (owner was absent) had warned me to keep an eye out for this due to the interference from the binnacle tube, but they considered the shifting to be acceptable.
Finally, I have a question. As inevitably happens, you put everything back together and one extra part remains. After reassembling my compass, I found the below sticker on my cockpit sole. The adhesive had dried and it fell off from somewhere. Any clues where it was attached?