James,
It is a purchased wire seal sold under the name of Ancor. You can use them on fish finder installations, bait tanks and general wiring on kayaks. They usually come with three different inserts that compresses around the wire(s), so you can also use them for a single piece of 14awg wire for running power etc. They are available here at
www.kayakfishingsupplies.com , and the individual page link is
http://www.kayakfishingsupplies.com/...re-Seal/Detail
Here's a photo of the ones I used to carry showing two sizes of inserts towards the right of the black plastic pieces. The top and middle inserts are the same (the top one is used), and the largest insert is below those two. Not shown is the insert that can act as a plug, or that you can run a single wire through if you want.
Hope this helps,
PerryC.