I have had a 10HP on my wigeon for about 20 years. As noted above, it weighs about 75lbs. That or a 15 (same weight on a 2 stroke) will work fine and won't stress your transom. I believe that the wigeon is rated for 7-1/2(mine is not at home or I would go look). The 10 will push it around 15mph loaded up, I think a 4 stroke is around 110. Anything smaller and you probably won't be able to get on plane. A trolling motor with battery won't save you much weight, but will limit you on how far you can go and how fast you can get there. I am not a fan of trolling motors in tidal water, no power and limited range. If you need to go a few hundred yards, probably not an issue but if you are going farther than that you are really cutting in to your hunting time and mobility. I found that adding a shelf under and along the inside of the gunwale made a big difference, the little ones that come on it are not of much use for anything. I have also added a couple of layers of glass over the years, really strengthened the hull.