I have a 14ft sylvan deep v on which I run a 69 evinrude fatswin 18hp (sh shaft). When (and if) I can someday afford to buy a new 4 stroke, what would be the optimum size tiller motor? I've been looking at the Tohatsu 9.8, 15, & 18. I'm a fisherman, so I'm not interested in pulling skiers. I...