You said it was the first time out? Fully charge your batteries and it should make a difference. The noise isn't really coming from the engine, it is coming from your alternator generating different kinds of currents. It gets complicated but the better your batteries are charged, the less noise you get from the alternator.
Make sure your grounds are all going to the same point in all your electronics. Electrons take the path of least resistance. If the electrons want to go weird ways, your amp makes weird noises! So lets make them all go to the same place!
Make sure your RCA cables are as far away from any power lines as possible! They like to interfere with eachother. If they absolutely have to touch because they need to cross each other, do it so they cross at one point at 90 degrees. Also make sure you are using good quality RCA wires with secure connections.
Make sure you have the proper size power wire. These amps should at least be on 4awg. And if they are all going to a distribution block, the wire from the block to the battery should be 0awg.
If all else fails go out on the water and try turning one amp on at a time to see if a particular amp is messing everything else up. If that's the case maybe it has a problem.