I am looking for a 77 inch (it's autohelm's model # 770X) replacement
belt for an ST3000, but Raymarine does not have one, and no one else
seems to either. Does anyone have a suggestion? Is there a way to
join the broken ends of my old belt that will do the job, at least for
a while? Thanks.
Those pulleys and belts (toothed, flat, V, or whatever) are not invented
from scratch, they are selected out of a catalog during engineering.
Take your belt to a good industrial supply house if you have one in your
area. Those belts come in all kinds but a good counterman there can
probably match it up for you.