You need to lock up your boats?*
I think just about everyone locks their boat in our marina.* At least everyone that I know or observe unlocking their boat when they arrive at it does.
Break-ins have occured, usually with the theft of easy-to-grab items like binoculars, hand-held radios, laptops, and so on although there have been a few instances of panel-mounted electronics being removed.
On old GBs there is enough of a gap between the edge of the door and the door frame to slip a credit card or knife blade in and work the deadbolt back.* So a couple of years ago I made up a stainless plate to cover this gap over the lock mechanism and bolted it through the door.* A determined thief will always break in somehow, but keeping a boat locked and, in our case, preventing the means from working open the lock, will deter the opportunistic guy or at least send him on to an easier boat.
We also lock our outboard to our dinghy and the dinghy to the GB.* Outboard and dinghy thefts are a problem--- not a lot of them but always three or four a year in our 2000+ boat marina.* The Port has camera monitoring, coded access doors to the main dock gates that are locked at night, and routine foot patrols but a person wanting to steal a motor can always find a way to get access to it.