l am 6'3 240lbs and l need help finding the size of a snowboard to purchase. I am a nooby and l want a board to take me to the next level also. l pretty much all mountain boarding. The question is what height and width would be good for me and do l need to purchase a ''wide board'' since l have a 12-13 size boot?

Well what im thinking is u need a 160 maybe. But the best thing to do is go down to ur local shop & see the boards for yourself. Hold up the board & if it comes up to about ur chin then u want that. A little shorter is fine but u really dont want to go any bigger than that. If ur toes hang off the board, then u want to get a wider board since u dont want ur toes sliding on the slopes when ur turning. But if u find a board u really like, but they dont have a wide enough board, what u can buy is somthing called binding risers or elevators. There the same thing just different names. They raise the binding so that u can use a wide foot on a narrow board.

Do not just pick a board between ur nose & chin that is a rookie mistake
You need to take into account a few things ur height,weight,riding conditions,riding style''all mountain,freeride,freestylefoot size & skill lvl
Once u get those nailed down u can narrow down ur board genre & size, Generally people go largest on freeride boards for stable carving & float in pow, Mid range for an all mountain board & smallest for those park rats.

Also u will need a wide with a size 12 or 13 boot, unless u want to deal with possible toe drag.

For the size on all mountain I'd look in the 160-165 range, You could very well get away down to a 158 but that is on the lower end of an all mountain board for ur height. Something to remember is the longer the board the more stable it will be for u when carving the shorter the easier it will be to spin it around butter & just dork around on runs.