The standard stereo was not amplified, however, many owners did add amplifiers. I'd check your wiring for corrosion at the speakers, and also at the dash loom connector. My boat had the wiring somewhat cannibalized by a car stereo installer that clearly hadn't done marine installs. All the connectors had corroded. Worst case you'll have to run new wire. It's not too hard in our boats, but you do have to remove the front seat backs to reach the wiring supports.