not familiar with mariner but i would start with your teather line to your vest, that switch would be where I start if its got one. What about spark? You may have a bad coil, most safety kill switches tie into the ignition circuit where if one is tripped the engine won't even turn over. You may just have a bad coil, test for power to the coil while cranking, if you have power going to the coil and nothing coming out that is your problem. After that I would get a manual or start with your meter from the coil and trace the wires back to every component that wire hooks up too. good luck.