I will pose some questions regarding your plans, and go from there.
1Q. Boat to be kept in the Bahamas. What about during hurricane season? Will one of the owners be on board the boat the entire time it's in the Bahamas? If not, what are your plans for a hurricane threatening the islands? Do you realize how high insurance will be for a boat kept in a hurricane zone? And the deductible?
1Comment. It is difficult for inexperienced people to get boat insurance, and few insurance companies will cover boats that are in a hurricane zone during hurricane season (in the Bahamas, that's from June 1 to December 1). Those that do offer coverage usually ask for either a "hurricane plan" or double the deductible for any loss caused by a "named storm" (hurricane or tropical storm). If the boat's a total loss as the result of a hurricane, you might be able to buy another boat, but probably not be able to get insurance for it.
2Q. Maintenance and upkeep paid on a quarterly basis. I'm unclear as to the mechanics of this. Are you saying that each quarter one of the four partners is responsible for payment of maintenance and upkeep? Or do you mean that total annual upkeep and maintenance is to be divided by four - the number of partners? Do you mean that during the quarter that a partner is using the boat, he is responsible for maintenance and repair costs? Does that mean that should the refrigeration go belly up during one partner's quarter, that partner is solely responsible for the repair/replacement of the gear?
2Comment. Maintenance and upkeep varies significantly over the course of a year, so the only fair way to allocate costs would be to annualize them, with each partner paying his share of the expenses proportionate to his ownership proportion. More: I would bet that with four owners, there would be four dramatically different ideas of proper and diligent care and maintenance. For a very short time we owned a boat in partnership with a friend. That friend never put away the sails or put on the sail cover after using the boat. The sail would be left exposed to the sun for weeks on end if Peter didn't go down to the boat to clean and tidy up after our partner used the boat. The guy just didn't understand how damaging the sun was to sails, and he also didn't realize how expensive sails were. He also seemed to be a bit fumble-fingered, and lost all the winch handles overboard and never bothered to replace them. "you don't need them anyway." was his statement.
Getting angry with such a partner is futile, IMO, because it usually won't change things. You have to plan in advance how the partners will handle the expenses and actual labor necessary to properly maintain the boat, and what to do should one or more not do their fair share.
Two good friends might be able to succeed in owning a boat in partnership, but I estimate that the problems will double with each additional partner added to this mix. Who will use it when, who is doing more work than the others, who is doing the most damage, etc., etc., on and on.
All that said, I have heard of multiple partners owning a boat successfully, so it happens. I just don't know anyone like that.
I think that maybe it could work if you took a really hard-nosed approach to it from the beginning and set out a detailed agreement before anybody had offended and felt it necessary to defend their approach to ownership and cost sharing.