reverse slipping?

[msmith10]

I'm sorry if this is a question that's been answered a thousand times already, but I couldn't find a similar post and I don't want to go to the books yet. This season, my boat doesn't seem to have as much thrust in reverse. The engine runs fine. Forward is fine. Neutral is fine. The boat does go into reverse, makes the usual "whine", but doesn't seem to have as much reverse thrust as usual. The only other difference I am aware of is that on it's first voyage of the year, the transmission shifted much harder than usual, although that is now back to normal. My neutral position seems to be the same on the shifter (pedestal mount) so I don't think the cable slipped, although I suppose that's possible.
Do I need to adjust the band? If so, do I need to adjust forward also, or just reverse. Sorry if that's a dumb question but I haven't studied the operation/adjusting procedure yet. I do have the rebuild manual.