Great idea wreck the boat diesel engine market for EU engine manufacturers like Volvo and MTU.Also resulting in a net loss of tax revenues for the government.It’s obvious that electric is the way to go for slow and small type river type use.Bearing in mind that the extra weight of the batteries is nothing like as much of a problem for a boat.
youtube.com/watch?v=UuZS6fpXii0
As for the legality of applying what is clearly meant to be road fuel taxation to boat fuel yet another reason why we should tell the ECJ to do one.
Having said that I thought this rule had already been implemented long ago. 
Meanwhile the other obvious solution but running on LPG assuming something like a Sunseeker presently running with big diesels. 
youtube.com/watch?v=4sx_AxoK7Cc
youtube.com/watch?v=7LQI5q-Hd6o
£5 per gallon they’re avin a larf. 
