I think the issue with the 6hp yamaha is that it's a 1 cylinder rattler. I'm not aware of any 2 cylinder 4 strokes less than 8hp made any more. Yamaha used to, but i think it was just a detuned t8.

I have the same issue with my boat, a little 14' wooldridge. I have a 75 2 stroke jet and currently use a 2 stroke 15hp yamaha for a kicker(hey, i already had it). It weighs about as much as an 8hp 4 stroke, maybe a little less. I'm considering just going electric for most uses, a 24v setup would probably weigh the same as a gas kicker.