It's not likely to really be adequate to the job, your speed will be greatly slowed down by headwinds, and unless it's a long shaft you may have trouble in even minor chop keeping the prop in the water.
This scenario can become quite dangerous if you unexpectedly get caught in bad weather/sea conditions.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)