goin thru tweeters like h2o

Hi all

First off  i need help with my boat audio...i think basics are the same as car.....2007 Nautique210 (see pic)....this could be really long so i am giving a very condensed version, if you need more detailed info just reply and i will provide what i can...anyway...tower speakers 4 Polk 4ohm spkrs wired to 2 channell amp (2 per) started cutting in and out not for long periods (ie cooling down) but for less then a second or so, volume was up to hear behind boat when turn down no more "sensored music"....dealer had stereo guy look...they unstaked amps, tht it waz overheating..did not work...he replaced the clarion amp driving twr only...didnt work....fin took to dallas high end shop...after 2 weeks dx was all tweeters were blown on twr spkrs ALL 4, external crossovers were @ eack spkr (POLK mmc650's 10 are in boat), gave some bs about attennuated music on ipod...anyway flash forward....today diff amp 4 channell bridged to sub + 2 channel cookpit (2 650's each)...let me say now that all pwr ratings are w/in specs....now 4 more tweeters gone...WHAT THE HELL IS THE COMMON LINK...not head unit it is pwring 21 front 650 no prob....any help will be greatly appreciated