I think that where you are boating an auxiliary is a must. As Polwart said, you're at least an hour away from any help at all and a lot of horrid things can happen in that hour.
However well maintained your engine is, bits can fail, as I found out last year when my engine stopped in the middle of the Sound of Jura (at least an hour from any help) late one evening. There's a thread somewhere about it.
My little Johnson saved the day and got me safe - and got me the ten or so miles back to home. Slow, noisy, smelly, using as much fuel per mile as the main engine would consume, but it got me back. How glad I was that I had it available.
Get one. You'll not feel lonely.