Vhb will outlast the boat, last fall I had to remove the the remnants of the window shades on my old truck and the tape was the only thing left.. tough stuff !
Guess what I'm saying is that if the upper gears destroyed themselves there are pieces of metal that have migrated throughout the drive and will be problem for the lower end..
Your picture is not conclusive but you stated the gears are damaged so that's what I go on...
Going into the top will not check out the cable but you'll get a good look at the upper gears. You need to pull the drive to change cable/ shift parts..
