I noticed the other day that the bolts holding my new 115 Yamaha 4-stroke that I had installed a few weeks ago are sort of "sucking in" the interior side of the transom - not sure if they just over-torqued the nuts when tightening them or what's going on. I'm also not sure how the transom is built - it sounds hollow when you knock on it, but I'm sure there's something inside for support, maybe honeycomb or something like that. (Now, before anyone gets started, the boat is a 2005 18 ft Xpress aluminum fishing boat, with all-aluminum transom. The boat is rated for 115 hp. And the 4-stroke is only 65 lbs heavier than the equivalent Yamaha 2-stroke. So it's not an issue of weight...) I'm wondering if it'd be useful to get some aluminum bar stock and double up on the inside of the transom? There's a support rib welded to the transom between the bolts, so if I added a chunk of thicker aluminum, it'd have to go vertically betwen the top and bottom bolt. I"m thinking a piece of 3/8" by 4" stock would really strengthen things.