Originally posted by Ghevd:

There is a work around. You place a loading ramp for your boat. Put a cart on the ramp. Fill the cart. Axe the cart. All the items drop in crates. Push the crates down the ramp onto the boat.

The video is a year old so not sure if they patched this out and I have yet to try it so attempt at your own risk.

https://youtu.be/M_JmUjYDnxA

Better to just drop a cart over the deck from a ramp, heaps of storage then.