I had a similar using VAOcean and I messed with pretty much everything in-engine I could find but the persisted. Just walking into a particular spot could launch the boat.
My solution of sorts was disabling the pawn’s collision with the boat itself and creating an invisible pawn colliding static plane that continuously moved it’s position to follow the boat’s last updated position. Not perfect but it worked, from there you could work further with it, maybe have a static non-rendered version of the boat as a pawn collision ‘ghost’ following the boat. Sadly disables the pawn’s direct interaction with the boat mesh but it’s something.
Sorry if doesn’t help, it was done under VAOcean’s buoyancy system which might work differently, but the way you described it it seemed like the same.