Re: how late in the season are boat still out on Simcoe?
End of October is it for us in the Parry Sound area. Mostly that's becuase the cabin water system is at more risk than the outboard

. Got a heated line into the lake but everything else is susceptible to ice-up.
Really, boat traffic drops right off Labour day and is almost nonexistant after (Canadian) Thanksgiving in this area.