Do you have any schematic for the switch? Is it a Single Pole or Double Pole?
Based on what I can see, that switch is only rated for 5A, which is likely undersized for the deckhand application, as the deckhand requires a 10ga wire. I'm guessing that it will pull somewhere near 20A.
You will likely need to wire in a relay to be able to handle that current draw.
If it is a single pole double throw (SPDT) switch(Up& Down), you will need to buy two SPDT relays to use it.
Can you provide a little more detail about the switch (which model, what ratings, and type (DPDT, SPDT etc) and where you plan on wiring it? Are you only using the anchor down switch and the original button for the up?
Let me know and I may be able to help a bit more.