I am not entirely confident in the security of my marina so I am thinking I need a better lock. What are you guys using to make sure you keep your boat safe?

Trimax and Reese locks both in combination. Don't forget about your prop(s),. Boat on trailer?

gorilla trailer lock.

I use a Maximum Security tongue lock. Rumored to be the best available on numerous travel trailer sites.
http://www.etrailer.com/Locks/Diversi-Tech/DT25013.html

Made by Diversi-tech

I've had issues with similar type locks fitting on my coupler, even though they say for 2 5/16" balls. They often don't fit around the flange on the coupler.
Steve

Here's what I use...
http://www.etrailer.com/Locks,Hitch-...k/1481DAT.html

Let's face it though, if a thief wants it bad enough he'll get it.

I have not tried this lock on my travel trailer (2 5/16") coupler so I can't speak to that problem but most travel trailers have a 2 5/16" coupler and the travel trailer guys recommend this lock. Very substantial unit.

locked in the shop, when outside i run a cable thru one side of the rims keeps them from pulling it off easily.

Lock on the coupler and a big-ol cable lock thru two wheels. The tougher you make it, the more likely they'll steal the one next to you.

I used that trick on my single axle trailer a number of years ago with a MasterLock cable. Then I found out how easy it was to part that bad boy when I forgot it one day. Hardly even felt it break. Kind of surprising actually.