Easy To Do

When you first take your dog off of the boat first thing in the morning it will do its business on the first piece of natural grass or dirt it can find---within 2-3 days this will become its favourite place for doing its business --once the 'place' is established then next time the dog needs to go then you have someone hold the dog back on the boat while you place a piece of artificial grass on the favourite spot---don't use inside-outside carpeting --too confusing---get the fake grass stuff from maybe a golf supply store---the dog will 'go' on its favourite place but will now be doing its business on the artifiicial grass--after about 2-3 days of doing this then start moving the artificial grass each day along the dock closer and closer to your boat ---within about another 2-3 days the artificial grass will be beside your boat and your dog will still be doing its jobs on the fake grass ---
Now comes the critical step --the next morning move the artificial grass from beside the boat up on to the boat (we use the foredeck) --bring the dog out of its crate (you do have a crate don't you) and take the dog up onto the foredeck (or whatever) where the artificial grass is located ----WAIT --do NOT leave until the dog has done its business on the fake grass --repeat again next morning--repeat again
After that it is really easy --for the next 4-5 days do not let the dog do its business off of the boat unless it has first done it on the fake grass sometime that day (preferably first thing in the morning when it really needs to go)
Also each time that you bring the dog to the desired location give it a command (eg: 'Go Pee') and when the dog does its business give the same command again AT THE SAME TIME AS IT IS DOING ITS BUSINESS --the dog will soon learn to associate the command with the 'action'--each time the dog does it at the desired location then praise the dog (good girl) ---be consistent and simple in your commands (same command and no additional gibberish)
Our 8 month old Brittany (who was already house-broken) learned the whole thing in about 8 days ---
Now --any time --even when bashing on a close hauled reach--- I can clip her harness and tether onto a jack line, tell her to 'Go Pee" and she goes up the side decks, does her business and comes back for her cookie
The fake grass is on a line and when we reach an anchorage the artificial grass goes over the side for 10-20 minutes (if the fish can crap in the water I figure my dog can too

) then I hoist it out of the water, let it drain and place it back on the deck
Training your dog to do it on board is almost an essential --especially if cruising in croc waters --besides believe me, your dog stops being your 'best friend' the first time you have to dinghy the dog ashore first thing in the morning after too many tequilas the night before:cussing:
Good luck --it can be done --just be patient and consistent and use the dog's natural instincts and desire to please you
Wannebesailor
Gozzard 36
Cruising in Mexico (with my best friend [& and my wife])