how long does a electric trolling motor last on a deep cycle battery?

There IS NO ANSWER to this question because it depends on HOW LOADED THE BOAT IS and how HEAVY THE SEAS ARE and how much the motor actually USES in Current. It can be anywhere from half an hour to 2 or 3 hours.. THERE IS NO ANSWER because YOU DIDN'T GIVE ENOUGH INFORMATION.. What does the motor DRAW in CURRENT and what is the RESERVE POWER in the battery.. without knowing at least THAT much, anything I could would not even be an educated guess

I'm kind of new but from what I've learned so far I'd say it depends on the motor wind,under current,boat weight,drag,amunt of people in the boat,just a ROUGH guess maybe 8 hours on the lowest speed 4 at medium and 1 at high in a small to medium size boat.Good luck hope find a good answer