Ideal world go for the Yam. Cost being considered the winner is Mariner as having the gears being built into the throttle is brilliant. You get used to the gears (my 7yr old did with ease) and it's much better than leaning around the side of the motor each time.
Tohatsu, nice option but not as robust as the others. Avoid the Suzuki DT range they've had their day. Selva is just not worth considering. Honda, nice motors but far too heavy being 4 stroke which is something to avoid at that size of boat/HP... Especially if your not planning on trailering it.
Saying that though it will still depend on each individual engine and it's history. I'd rather have a pristine Selva than a worn out yammie....ok maybe not but you get my point!
Peter @ Boatsandoutboards4sale ~ firstname.lastname@example.org
~ 07930 421007