boat alarm, first time

i want to install an alarm in my boat, but what i need is very simple. all i want is some type of magnetic switch or door pin installed on my console door so that if anyone tries opening it the alarm will go off. I found the merlin 2000 and i think it'll be perfect for what i need. The only thing holding me back is the installation. Can anyone help me out with any tips/ideas/suggestions? How would i connect the door pin/ switch? any help would be greatly appreciated!! thanks

well running the wires wouldnt be much trouble. all i really want to know is how i would wire up the door switch to the alarm. Is this even a good idea? Is there any other way i can set it up so that if anyone tries opening the hatch the alarm will go off?

Heres what the boat looks like http://www.seaveeboats.com/preowned.html

Click the 340B TRIPLE OPEN....theres a picture in there with the hatch open (you'll see a toilet inside). Thats where i DONT want people getting into.

You could do several things:

1) you could purchase a simple magnetic switch, install one half of the switch on the underside of the hatch door, and other on the hatch jam side. 

2) Purchase any simple car alarm (you'll need a 12 volt source -- if you don't have exactly 12 volts from your battery output, you'll need a convertor) that will be triggered by the discontinuity of the magnetic switch.

3) the alternative is to purchase an automotive door pin switch -- usually a rubber covered metal spring switch that is grounded when door open, and carries a positive voltage when the door is shut.  This can be used somehow if the magnetic switch won't exactly "fit" on the hatch or line up properly.

4) most bettery quality brand alarm system will allow inputs for several types of detectors/sensors: vibration, motion sensors, etc.  All of these can equally be implemented in your boat.