I don't recommend shifting from reverse to forward or from forward to reverse without pausing in neutral for just a second.
While I suppose your shift rod could be out of adjustment, it doesn't really sound like it. If it selects both gears, that's what is considered "in adjustment".
Check to make sure that the clevis pin at the top of the shift rod is correctly installed in the clevis and that it's cotter pin is in place. If those items are properly in place, the shift rod "joint" (item #3 in the link below) cannot turn and become out of adjustment.
https://www.boats.net/catalog/honda/outboard-by-hp-serial-range/8hp/bf8ah-la-pre-1997/extension-case
Is there any grinding or "chattering" noise when you shift? If so, it may indicate that the clutch engagement.surfaces are worn due to improper shifting habits.
These transmissions last the longest if properly shifted. Select each gear from neutral with a quick and firm movement of the shift handle while at idle speed only.
Going from forward to reverse or from reverse to forward, without pausing briefly in neutral, will prematurely wear the clutch. Worse yet is to s-l-o-w-l-y select forward or reverse from neutral. This action will cause the clutch to "chatter" as the clutch "dog ears" tend to bounce off of each other instead of engaging immediately. This "lazy" use of the shifter will cause the most clutch wear the quickest.
I am very disappointed that outboard manufacturers don't usually include ANY instruction in correct shifting in their owner manuals because, intuitively, most of us think "slow and gentle" would cause the LEAST wear. But, in shifting an outboard, it's something of the opposite. "Quickly" and "smartly" are words that come to mind for gear selection for an outboard transmission.
Have you serviced the transmission recently? If not, I recommend draining the gearcase and inspecting the condition of the oil. Look for any sign of water intrusion or metal particles.
Let us know what you find.
