Hydrogen 9.9 worth a read

[FMP]

https://www.researchgate.net/publication/267576511_A_Hydrogen-Fueled_Direct-Injected_Two-Stroke_Small-Displacement_Engine_for_Recreational_Marine_Applications_With_High_Efficiency_and_Low_Emissions

[XstreamVking]

Forward thinking for sure. Be cool to see in operation. Wonder how big the fuel tank would have to be?

[FMP]

2.5-3: 1 fuel capacity for equal range, SAE has standardise fueling for auto. Takes three minutes to tank up a fuel cell car for equivalent mileage per tank. Larger hulls could make it work. 100% feasible with supercharged four strokes like Varado, Seven, or popcorn Yammi