Boat cover for 14' fishing boat
this thread linked here has some other cover makers mentioned
there were other threads on boat covers too, but not sure they're still around
get your dimensions from tip to stern, beam width, the look around... you can usually ask the vendors more info before you buy as well
I know that a poor fitting cover won't last long over a long trip ... the wind can rip some pretty sturdy looking material in a hurry, or cause wear spots where it goes over any sharp spots...
...so you will want a tighter fit over a looser fit...make sure to put a towel or something over a trolling motor, or some sort of mount to keep the vibration/wear to a minimum