Motion manipulation on Boats

I tried making speedboats with commandblocks - the user pays 1 emerald for 15min 1.5x speed
Using those commands (wich should double the speed) I got no results:

execute as @e[type=boat] store result entity @s Motion[0] double 2 run data get entity @s Motion[0] 1
execute as @e[type=boat] store result entity @s Motion[1] double 2 run data get entity @s Motion[1] 1
execute as @e[type=boat] store result entity @s Motion[2] double 2 run data get entity @s Motion[2] 1