I would think in the summer with lots of extra daylight the trip is doable in a day. A very long one at that and it needs to be the right day with good wind
But for you it's not doable should you get some "weather". It tends to mean you have to pick the weather
window and be ready to cancel or lay over if things don't look perfect to come back the next day. Coming back is the hard part as the pressure to get back tends to make you think you can do more than you can. I'm sure you understand what is in between Duluth and Two Harbors so it's not like a lot of places to hole up if required. You pretty much need to go all the way in one shot. You also don't have a lot to look forward to if you end up in the water
I would do the numbers on fuel
so you could complete a trip most of the way under power if you had to. In rough weather
the outboard engine
could be a problem keeping it from being totally submerged. Going a great distance off shore adds to the distance. Being pinned against the lea shore would be disastrous in any thing worse than not such a nice day. If it got really bad I'm sure they would find the boat but it might be empty. The boat is clearly more than able if you use it properly.
If all you have done is sail close to the harbor day sails
then you might want to spend a summer just getting better. You'll need to come to terms with a lot contingencies as well as planning for some support if for nothing else to provide communications
and weather information along the trip.
Getting more experience wouldn't be a bad idea and trying something a little shorter for a dry run would be a good idea too. I would try some very short out and overnight then back trips just as a way to shake things down. Might all be fun too. The kicker
to all this is Superior can make it's own weather and weather reports are not like they are in the Cities. In the 28 years I did hiking and canoe trips to the north shore I never found the weather predictions that great, but on the right day it could be a lot of fun.