So, my wife and I were in a partnership situation w/ another married couple for 5 yr in our Pearson 30 in FL b/f we bought out their interest and moved that boat to CA. In terms of questions, I frankly would be reluctant to enter a boat partnership with “strangers.” We knew our partners socially and were friends before committing to a boat partnership. Plus, we shared a wider group of sailing friends. We also held similar political views and could talk about them, etc. They were knowledgeable about boating having spent time in early marriage delivering a boat or two, etc. They each had jobs. So, we knew a lot about each other. Still, we had a written agreement regarding use of the boat that we both respected.
So, the important questions for strangers, if there were any, might be.
“Could you afford the cost of ownership of this boat on your own for at least 3 or 4 months?” I think it’s folly to enter a partnership with someone who could not afford to carry the boat if something interrupted the partnership, such as temporary loss of significant income from one or the other side.
“How many days / weeks / weekends per year do you anticipate using the boat: how, and where?” This number has to be in the range of someone with regular local commitments. Such as one, or at most two, weekend(s) per month, or a month or less per year of continuous use, etc. No taking the boat to Mexico or to the Bahamas for six months, etc.
“What routine maintenance tasks could you do on your own?” Such as, change primary and secondary fuel filters, change the oil, tighten the belts, inspect or repair other systems, including electrical, etc. Let that person come up with them.
“How stable is your employment and family relationship?” Since I’m not the government, I think it is OK to ask about personal situations, etc. As many know, job transfers and divorce or other types of family breakups can kill partnerships with nasty consequences.
I might also have to work in some politically-nuanced questions such as views on certain kinds of regulations and respective compliance questions, etc. The kinds of things that might get the boat in trouble if not properly attended, etc. Including stuff that might lead to arguments among the principals.
From acceptable answers to these basic parameters, a written partnership agreement might be possible.