I bought a boat with a clarion cd/stereo head

I bought a boat with a clarion cd/stereo head unit. I noticed a problem while trying to play the radio that the speakers continually cut out. I get music for 2-3 seconds, then a popping sound, followed by no sound for 1-2 seconds, and then it repeats. I installed 4 new speakers because the old ones were junk anyway. The stereo sounds great with a CD, but it does what I described while trying to play the radio. When I scan for channels also, it does not pick up any stations. All the speaker wiring is good, obviously, since it sounds fine with a CD. I have unplugged the antenna and plugged it back in (did not help or hurt). Any ideas?