Hand tiller outboards-Which would you choose?

Yamaha/Mercury 30 hp 747cc 3 cyl. $3500
Yamaha 25hp 498cc 2 cyl. hi-thrust model $3200

Suzuki/Johnson 25 hp or 30 hp 597cc 3 cyl. $2700 or $3500

Nissan 25hp or 30 hp 492cc $2800 or $3000

Honda 25 hp or 30 hp 552cc 2 cyl.$3500 or $3800

Going on a 18' Sea Ark MV1872 heavy duty (.125 aluminum) "super" jon
boat (80 hp max?)
fuel efficiency most important. Cruising at moderate speeds, around
15mph is the goal.
Is this underpowered @ 25-30 hp?
Thanks!