Add more speakers?

OK, I got my tower speakers installed with a 70 watt per channel amp, and tried them out but could barely hear them over the motor and wind. Should I build a second set and get a larger amp to run the two sets? I know that getting a larger amp does not equate to louder, since it takes a significant rise in watts to increas Dbs a small amount. I also understand about pushing more air with more speakers, but should I add a stronger amp to power four speakers, or will the 70 per channel (which turns into 140 per channel at 2 ohms) be enough?

Ok, the second part of this question. I have the Infinity Reference 652i speakers, and a Bazooka BAZ EL260 amp. The Amp is rated at 70 watts RMS per channel, and the spreakers have a recommended RMS of 65 watts with a peak of 180 watts. I am not sure what the amp peaks at (specs onthe web say 300 x 1, so I am guessing 150 x 2). I am running the Pioneer DEH3500 head unit which is rated at 22 watts per channel rms.

So with all that in mind, if I add a second set of 652is, should I upgrade my amp to a higher rms power amp? I am trying to get loud, clear sound that I can hear behind my boat when I ride. I have an outboard, so it is a little louder than inboards. With what I have right now, I can hear some of it a little when I ride, but not enough to even know what song is playing.

Advice please? Which should I add first?

Chris, your question is kinda puzzling. You have the power for the speakers if thats really what you amp puts out. I have infin. rfs on my tower with 75watts to each and they blast!!! Double check your amp settings and your head unit settings. If it all checks out then try a different amp but the referance series speakers are plenty loud. 4 is allways better then 2 but i have heard a lot of boats with just 2 up top that are plenty loud. For the record i went with 4 6x9's and a JL300/4 set up on my tower.