How do I slow down slowly

so i have a boat that has custom movement.

somewhere on press W i set it's custom movement speed to 50 - and it works good. then i release the key

and i want it to slowly get down to 0 speed.

i've tried:

system every 1.0 sec && boat.custommovement.speed >0 set boat.custommovement.speed-10 - doesn't work

tried the same invoking a function - doesn't work

tried the same with every tick - doesn't work

tried recursion in function - breaks the javascript

so how exactly do i do it correctly?

I'm not sure how custom movement works, but try

W is down -> Set speed to 50

Else -> Set speed to max(boat.custommovement.speed - (60 * dt), 0)

(to make an Else event, select the "W is down" event and press X). Change the 60 to a lower value so it slows down slower