What do you use to remove odors from your boat?

[qlboat]

My boat was bought second-hand, and I rarely use it. I only use it occasionally when I go out to play with my children. There may be something else (small animals or something?) and then there is a little odor. I can't find it.
See how to remove it. What kind of machine can be used to remove the odor? Air freshener, or some oxygen machine, ozone machine, etc.