Re: solar recommendations
On a boat at a marina it is helpful to angle the panel. On a mooring flat is better.
On a sunny day figure 5 hours at full output unless in the south where 6 hours is a better guide. Obviously less on a cloudy day. The northern hemisphere has pretty good sun angles in the summer - few cruise in the winter.
There is a gain to using a MPPT controller - 15% or so.
A 100 watt flex panel is 21" x 42", solid frame panels a bit larger. On a sloop aft is the best location - on a pole, mounted on the stern rail or on each side, or on an arch on larger boats.
My customers do not have the issues that your friend had. Good installation with proper cabling and a good quality controller - MPPT preferably - gives good results in the cruising season.
Living aboard in Victoria Harbour