We got our dog when we were living aboard
, and we trained her from day 1 to use the astroturf on the bow (or below in bad weather). When she was three months old, we then had to teach her that it was OK to go on grass! It took several long days staying ashore before she'd "get busy" (our magic phrase) there -- she was convinced that the only correct place was on the boat.
So, yes, it will take some patience. If you can, get a piece of Astroturf from another boat with a dog that already has the "pee scent" on it. Put it on the bow and your dog will quickly sniff it and get the idea -- this worked for several friends.
Perhaps the bigger problem with a greyhound will be getting enough exercise. Our dog is small, so she could run around on the boat when we didn't go ashore for various reasons.
All said, our lives -- not to mention our cruising -- we were greatly enriched by having Paz with us. And she loved the boat. Now we're living on a small lake and she considers the dinghy
(yes, we got a dinghy
for the lake) to be HERS -- she just lets us drive her. And when anybody motors by, she always asks to go for a ride. So, no, I don't think she suffered by having to live aboard!