I have a bow mounted MinnKota on my 1800. I don't know the shaft length, I'll measure tomorrow. The shaft is a long one, and I like that. When there are waves or chop, it stays in the water. If the waves are too high, I don't want to be using it anyway. Time for the outboard.
The amount of shaft below the bow is adjustable on mine. If I was buying one with an adjustable shaft, I'd get the longest one I could.