In short I'd thought id ask before I built one, how much weight would a long tail with a 5.5 horse honda engine push? Ie boat and load weight..
The only reason I ask is my 16hp weighs a ton and I scored a wee honda commercial yesterday for next to nothing and I thought it would be a light wee unit for me and the dog to go for a fish with.

It depends on your definition of "push".
It will push you and your dog along at a little better than walking pace and it won't push you through straight mud by any means. Probobly whenever the boat touches bottom is when you will start pushing.

I also urge you to try and find a flatbottom boat.

I have a home made 5.0 hp OHC honda LT that I have run on a welded 12/36 hull, with my 220lb,100lb wife and another 100lbs of fish,gear and gas it moved us along just fine, no speed demon obviously but it was definitely not a snails pace by any means. Thats a OHC motor which isn't ideally suited to this application, a OHV would be even better. With just myself I had no problem going through mud and over fallen trees.