Bikes on your boat

We like to take weekend trips on our boat to different river towns. I would really like to haul a couple mountain bikes with us to use when we are tied up to a dock. Has anyone out there ever attempted to somehow hang bikes from your tower or board racks so there is still room in the boat. I have an 07 MC X45. In the past ive taken a fold up bike and put it in one of the rear storage lockers. However, it would be nice to haul a few real ones so everyone would have a way to get around. 2 to 4 bikes max. What do u think?