I believe that the difficulty is associated with the isochronal routing algorithm. The same problem occurs for me whenever I set both my Michigan and Wisconsin exclusion zones (race notes) to "Yes" under the "Avoid" column. When I set either note to "No"  then an isochronal route is produced; albeit a different route depending on which note is set to avoid. The two isochronal route are up to 40 NM apart and they finish 45 minutes apart.   

Neither of those routes is the same route that is produced when the grid algorithm is selected but all three routes finish within an hour. Note that I am routing to a "speedpoint" approximately 10.5 NM WNW of Point Betsie.

I believe (not really certain here) that the isochronal route was developed for longer offshore legs that would not be constrained by exclusion areas defined in race notes.

Good luck in the event.    

Thanks for the info,I figured as much.  Will you be racing as well Joe? 

Last edited by justinkalb (7/19/2016 1:37 pm)