my 14' richline wont, it pushes it at 8 with 2 guys and 2 kids or just 2 guys, It will plane with me alone and do 12mph. get a 15+hp if you have a choice.
I've seen a 1436 flat bottom G3 w/ a 9.9 honda plane with two adult males. There was no additional gear in the boat. Passed by it w/ a 1648 loaded down with gear and one person with a 20HP 4 stroke yammi.
That thing will run great with a 9.9 and two adults! The Honda may take a little longer to plane off than a comparable 2-stroke but it should do nicely.
I was worried about that too with a 25 HP on a 18 Ft Jon, but seems to work well, with the boss (wife) and me. And she grew up on the lake so she likes fishing..I think you will be fine, but you could get a 15 HP for not too much more..
my g3 guide v 14 with a 9.9 2 stroke would't plane with 1 person and all my mods plus 2 deep cycle batts. its way under powered.plus a 4 stroke is heavier than a 2.
I got a 1448 with a 8hp 4 stroke, Its ok with just people, but when I load it, it struggles, i'm upgrading this winter if all goes well. the best I did with it was 19mph on GPS runnung down stream with just me and my son, normally its around 14mph