Why won't you just go with 9.9 hp , I think that will be plenty,
myself I am getting 6 HP - 4 stroke for my 10 ft zodiak this coming season,
the weight of the motor is about I think 55 - 60 lbs, where the 9.9 will be about 85 - 100 lbs, friend of mine got a 2 stroke 6hp and needs someone in the front to hold down the boat steady
, he's runing it on a 10 ft zodiak.
Hope this helps,
Cheers !