In the past we have run a year long usage calendar, week by week. We run a spreadsheet to record maintenance, costs and monitor individual spending and ensure balance.
Remarks
A 3 way share arrangement worked really well for us. But buyers are hard to find. I've decided to look for a half share buyer.
I highly recommend this as an affordable way to own a yacht.
People are often reserved about share arrangements, because of the risk of disagreement. We had a 3 way share for four years with no problems. And achieved a lot of work on the boat.