hi a was wondering if i am correct that a lower kv motor should be able to swing a bigger prop then a hi kv

That is correct, however it matters how much voltage you put through it. If it is the same voltage for two different kv ratings, the lower one will spin a bigger prop. What is your setup? how much kv?

well it is my boat that i was killing my esc in now my motor and my esc has arived
the motor is kb 4508xl 1700kv
the esc is also what was recomended a turnigy plush 100amp opto
going to run subsurface in a multi hul style boatit is about 36 inches long