I have the opposite experience - lots with bikes, zero with motos - so I really can't help you here. Perhaps it will work, but as I mentioned, it's unnecessary as skeg cables are relatively short and fit loose in their housing, so dripping lube in from one end and working the cable back and forth is enough to distribute it. Also, it's not easy to detach the housing in some skeg systems, so you wouldn't be able to attach the tool anyway.

The simple solution is:

1- Prop the stern of the boat up on a sawhorse or something similar, with the hull upward.
2- Drop the skeg so you can access the cable.
3- Run water into the skeg box.
4- Work the Work the skeg control back and forth to help flush out any salt/grit.
5- Drip cable lube down the cable and into the housing.
6- Work the skeg control back and forth to distribute the lube.
7- Repeat until there is evidence of the lube at the control end.