Re: Battery to engine
Accessories (radio with a clock and memory function, etc) that draw a small amount of current will cause a slight spark. If its a rather large zap you see, yes -- you have something wrong. Make sure the positive battery cable connects to the large post on the starter solenoid (not the starter). The other large post on the solenoid goes to the starter. The negative cable simply bolts to the engine block. You might try disabling all of the accessories on the boat by removing their fuses. If you still get a spark, something else is wrong.