Hello, I have a 1987 sundancer 300, with twin 350 chevy motors. One engine starts fine and runs good, The other engine has been giving me some trouble. So recently its battery would end up dying when we are out parked at the sandbar all day. In which cases I would use the emergency start switch and jump power from the other batteries. But recently now the battery doesn't die. The motor will just crank and crank and crank but will not grab and fire up. I replaced the starter because it was glowing red hot and shooting sparks when the key was turned. Didn't fix the issues. So i replaced the ignition coil, distributor CAP, still didn't fix the issue. We sprayed starting fluid into the carb and it still wont grab and fire. So its getting power from the batteries, its getting fuel, it has to be getting spark right? If the engine is cranking then its getting spark? I don't know I have a feeling it is something small and easy to fix and were just over looking it. Could it possibly be a fuse or something thats blown out that wont let the engine start but crank? Could it be a kill-switch possibly hidden somewhere that one of my drunk friends maybe flipped while on the water. I mean it cranking shows me a good sign that its wanting to start but just something small is not working. thank you for any advice you have, I am new to this big of a boat and twin engines.