If you'd not cover that water
ill equipped on your own boat, why do it on someone elses?
Plus maybe worth checking out the trip is fully insured and you're not carrying any kind of liability as crew.
There's a relatively recent but well known local case where a delivery skipper
paid his mate a hundred pounds to help him move a large power boat
from the Solent to Poole (around 10 miles).
but they put it on autopilot
, ran around the boat tidying up kit, and whilst heads down the boat hit a navigational buoy flat out. It holed it above the waterline but when slowed, in it all came.
It sunk. They got away safely. But the 'delivery skipper' AND the pal who crewed were taken to court by the insurance
company, judged to have been at fault, and collectively costs were awarded against them both.........
I believe it bankrupted them both. So check that out along with your safety
issues and hopefully you'll have a safe enjoyable trip.