We split the provisioning equally and have a boat kitty for mooring fees, etc. For activities or eating out, we use a smartphone app called Travel Money (Android - I'm sure there i versions). You put in the people (or couples) and then when someone pays a bill it automatically splits the charge among them or you can specify a different split if you want. It keeps track of who owes who how much. One person can pay and have everyone reimburse at the end, or what we do, is rotate payments and try to keep it roughly even and then settle any differences at the end (which is usually very minor. It's really very easy to use.
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