Ive got a little 12foot jon boat Im thinking of putting an outboard on , was gonna use it to run a river I love to fish that I cant get in with my bigger fiberglass boat during the summer months because the water level is too low. Lots of people fish this river in jon boats. This particular jon is rated for 5hp, my question is how well is a 5hp gonna push the boat didnt know how fast the boat would run or if it would get me upriver with a 5 on it. The river Im speaking of is the Pearl River, I live in Columbia,MS for those of you who have fished the Pearl. Its not a huge river or anything but has some great back water bassin. So what you think will the 5 do what I want?

My 12 foot Vee gets pushed with a 4 hp Evinrude.  It pushes us (Dad - 225# Me 140#) at an estimated 4 - 5 mph or so.  

although, I think you can put more on that boat without trouble.  The rating is based on size, and not strength or anything else for that matter.  Round here, jons are always overpowered, and never much trouble.

You should be fine with the 5HP.

I run a 9.9 on a triton 1650SC, floor and side panels, is a perty heavy boat.

But with 3 of us me 200# my buddy 180# and lil guy @ about 100# I'm guessing it putts along 8-9 MPH.

Thing is, your travel time is huge at slow speed, so you have to always be aware of the weather and how much time you need to return to the ramp.