It definitely makes sense for some applications. For example, I believe Uma was running their electric motor purely using solar for charging for a few years: https://www.sailinguma.com/electro-beke Not a huge amount of solar either - 480W of panels on a 36-foot ocean-going sailing yacht, shared with all their other electrical needs. It worked for them because they were primarily sailing, with the motor used briefly for maneuvering in tight areas like harbours, so they had plenty of time on passage and at anchor to recharge the batteries between each use. (Their current setup has regen, so they can charge the batteries by sailing - basically a very indirect form of wind power. Some small sailing boats have actual wind generators but those are loud and take up space.)

For speed boats? Probably not. Those things are small and incredibly power hungry - going fast on the water is expensive in terms of power used.