Heat shrink and lug boots

Adhesive lined 3:1 heat shrink, and the same material pre-cut into 100mm lug boots so you are not measuring and cutting tube on the bench.

Adhesive lined matters. Plain heat shrink grips the barrel but leaves a path for water to wick down the strands; the adhesive melts as the tube recovers and seals the joint properly. On a boat that is the difference between a crimp that lasts and one that goes green inside a season.

Size it to the lug barrel rather than the cable, and use red on positive and black on negative so the polarity is readable at a glance in a dark locker.