Having used the RAM mounts on my last boat and new boat, I can say they are very good. The ball that the RAM mount mounts to is rubber coated to reduce sending the shock through to whatever it's mounted to.
I had my old Garmin III+ mounted on my old boat and this big Lowrance LCX-15 on my new boat with a 1" RAM mount. Though I am considering switching to the 1 1/2" ball for the bigger Lowrance unit. Attached is a picture of the unit you can't see the RAM but you can get an idea of how big a unit can be on a RAM mount. I also have my camcorder mounted occasionally to the boat with 5" RAM arm...