re: Boat Motor won't start - help

Try pulling the positive/ negative lines off the battery( starting battery) scrub them clean with sand paper. Had that issue, there was corrosion on the terminals. Not very noticeable, but it was there. Those motors pull a lot to crank, if there is the least bit of corrosion on them they won't crank. My stereo, vhf, and gps worked fine, but as soon as you turned the key to crank everything would die.

Also might want to think about adding another battery to your setup, one for all of your accessories, and one strictly for your cranking.