Are Merchant Navy officers ever armed (officially or 'unofficially')?

nope,weapons on merchant men cause a lot of difficulties,insurance etc,been merchant myself,a friend was sent to angola to join a ship a couple of weeks ago,with pirates they are taught to shout at them,stick a spotlight on them hose them with fire hoses,wich is all well and good when you have a bunch of ak 47s and rpgs' pointed at you