There are 3 major factors that should drive solar
system design on a boat.
1. Lack of space.
2. Weight considerations.
3. Potential for partial shading.
#1 and #2 encourage one to use the most efficient panels
one can find. #3 encourages one to carefully position the panels
to minimize shading and wire in parallel or one panel per controller to minimize power losses.
There is a solution that nicely covers all of the bases. Sunpower panels are over 20% efficient and come in 327w panels, yet are the same size as most panels. 61"x40" and only 41 lbs. If one were to buy 5x 100w panels, not only are they doing considerably more work wiring
it all and screwing in 3 more panels, the total weight could be considerably higher.
Since each panel could put out up to the following under optimal conditions:
327w / 15v = 21.8A
327w / 14v = 23.36A
327w / 13v = 25.15A
327w / 12v = 27.25A
I would recommend a 30A MPPT
controller for each, or a 60A controller for both.
The Sunpower panels are more robust and capable of longer life under temp. extremes, not to mention much less loss from shading than other panels. There are youtube videos explaining all of this. The hard part might be finding the panels for sale
somewhere, but they are available.
If you have room for 5x100w panels, you probably have room for 3 or 4 Sunpower panels. You can never have too much solar
power, imagine having 3 panels and almost 1,000 watts, or 4 panels and over 1300 watts!