Winter is here, can't use motorized raft

Im near Moscow, and want to head south. Problem is, it's winter. I can use the motorized raft on its own with some fuel, but can't pick anything up, because it still marks me as having 100 kg weight limit, not the rafts 400 kg. I don't know if it's because we're not meant to use raft in winter, or it's a bug, or I'm doing something wrong.

I tried dropping the raft, picking it up again, and clicking use, not helping tho. Still stuck on my 100 kg allocation.

Anybody else had this problem? Have a ton of stuff to take south with me!