https://www.jamestowndistributors.com/userportal/document.do?docId=783
For an outboard, measure from control box back to transom then across the transom to the motor. Most say to add 4', which is what I did, but it seems a little much. I could probably knock a foot or 2 off my cable length as I have a lot of extra cable in the back of my boat. Doesn't hurt anything, just seems to get in the way from time to time. But definitely better to be a bit long than too short.