I have what I believe to be a 1983-85 90hp Johnson V4. After only running on a used fully charged marine battery for 3 weeks the battery was drained. The battery was reading about 12 volts but drops down to 7-8 volts when trying to start the engine. At least that's what the boats battery gage reads. Luckily I had a spare battery and hooked them up in parallel and the engine started. Could this be just a bad battery or is the alternator/generator bad? Any comments greatly appreciated.
