Is it wrong to cheat at board games?

Like, say for example, is it wrong to excuse yourself from a game of Monopoly that you are playing with a group of friends so that you can go to the bathroom and inside offshore pharmacies said bathroom you have a second Monopoly board game hidden under the sink which you fish $500 bills and hotels out of? Also, what about moving your boats around on Battleship? Sometimes, I realize mid-game that I actually meant to put my boats in different spots.