Jeff it depends on lot of factors.
The biggest is the effency of the high power users especially the fridge / freezer
The other side of coin is where and when and how you will be using the yacht.
has quite good insolation in summer, but not great in winter (do you want to use the yacht year around). Will there be other sources of power especially shore power
If you want a proper answer you need to measure your typical power consumption
(in AHrs) The easiest way is use a battery monitor
which is almost an essential anyway.
For a rough starting point 300w in summer and 600w for winter, but these numbers could be out by a factor of 2, or more.
Without more involved measurements a common technique is to fit the largest solar
array you can reasonably fit and hope it is enough. Solar panels
and this is not a bad philosophy, but it can lead to disappointment if the panels do not supply sufficient power, or frustration where more money
spent on high efficiency panels might have made the system self sufficient.