this is a trick a local marine electronics installer taught me 20 years ago. instead of putting the little screws and cable ties in the transom. put a "Hersey Kiss" of 5200 on the transom and lay the cable in it. then tape it so it won't move and let it cure. no holes to seal or ties to replace. this one has been on this transom since '89.(hard to see but below the drain hole on the starboard side)
