When you place your share up for sale you are required to show the weeks you have booked on the web site.
Comments like "To Be Arranged", "Ask for details" and "By Negotiation" etc. are not permitted. If nothing else anyone reading the advert will just move on to the next one, so it does you no favours!
If you own a share in a boat you will KNOW what weeks you have coming up, so there is no reason that they cannot be shown, indeed they are a major selling point.
However, sometimes two vendors with get together and place ONE advert to try and sell their two shares (and save money?) and to be fair to ALL advertisers, wherever possible, this is stopped.
If you are trying to do this then the best you can do is advertise one share and against the weeks make a comment like "These could be negotiable". However, the vendors would be far better off placing two adverts as one of the first thing people look for when buying a share is the weeks that go with it, as there is no point in buying it if you cannot use it!
You cannot materially alter the booked weeks unless your advert runs over the "booking cusp" so if your advert is showing your weeks for this year you can make contact and add your weeks for a later year once they become known.
THE ONLY EXCEPTIONS ARE:
New boats, where somebody is trying to set up a brand new shared ownership boat.
Shares for over 1/3 of the boat.