I have a 14 foot flat bottom looking to get a new motor the old 73 thats on it sat too long I guess. No one around here will work on it was considering 9.9 mercury but didn't know if that was to much or to little. Any thoughts?

I have owned a Alumacraft 1436, 15hp mercury 2 stroke, 2 guys with gear pushed it 21mph, friend had same boat with a 25 did 30mph. I thought the 25hp mercury 2 stroke was overpowered and put to much weight on the aft.

A 9.9 or 15 would be ideal if an older 2 stroke.
If you put a 25 on your boat, (and you should do this anyway) wear your PFD and tell someone what time you are to return and where exactly you are going.

Yeah 25 might be too much and definitely more money than I planned on spending. 20 MPH is plenty to get me anywhere I plan to go just didn't know if i could get that out of the 9.9 or had to jump up to 15.

On your size boat the 9.9 would be plenty, but if you may upgrade the boat for something slightly larger in the future the 15 would probably be better, but that slightly more speed with the 15 comes with a higher price tag as well.
I'd stay with the H.P. rating on the hull tag at the back of the boat if it's still there.
You have to be on your game in a small jon boat, as weather and other factors can turn on a dime!

Had a 1436 years ago 15hp pushed it around 20. I miss that little boat..think I caught more fish to.

Compare the weights to the motors you are looking at. I have a 14ft fiberglass skiff and put a 25hp Mercury on the back. In hindsight I should have went with a 20hp. The 25hp has 5 extra horses but he motor weighs 55 lbs more. A 15 and 20hp Mercury both weigh around 105 lbs.

I had an Alumacraft with a 15 merc 2 stroke. It moved along fine. No cup holders, so the wife wanted a bigger boat.