Engine kill switch

[sailingharry]

I know this is more a sailing forum, but a boat is a boat, right? I've just acquired a 17' bow rider, with an I/O. The kill switch is inoperable -- mechanically frozen. The PO (or PPO?) bypassed it by removing all the wiring! I'm looking to replace it, including running a new wire to the switch.



Unlike many outboards, that kill by grounding the spark, this kills by interrupting the ignition. According to the factory wiring diagram, it actually kills power to the ignition switch. This means that the little kill switch carries all load for the ignition -- but also the start circuit all engine instruments.


To my way of thinking, I'd rather not run more load through that switch than needed. It stresses the switch, and it adds resistance to those circuits.


Is there any reason why I shouldn't rewire it to only interrupt the wire providing power to the ignition?

[SY Harmony]

You could use a relay near the ob and shorten the high amp runs.

[Lou-In-NJ]

Since it sounds like this is a gasoline engine you're talking about, first I would use a sealed switch, not only because of the water environment, but because gasoline fumes are explosive and even at 12 volts you can get enough of a spark to set things off under the right conditions.

Also, current draw on the ignition system is not usually more than an amp or so, and instruments probably total less than an amp, so I wouldn't worry about loading down anything, unless you are adding in the current draw of the starter solenoid, in which case you can add 3-4 amps more; still I'm sure you can easily find a switch that can handle 5-10 amps.

[sailingharry]

The switch is a proper marine kill switch, looks just like the one in the side of your outboard (a button, with a red clip on it). It doesn't actually say "ignition protected" on it, but it's a SeaChoice and looks to be water/ignition sealed.


It is rated for 5A, which is probably enough.


I guess my question isn't "Will it work as originally installed," but rather, "Is putting it in the ignition circuit BETTER than original?"


In either case, I'll remove one wire from a terminal on the ignition switch, run it to the kill switch and back. Exact same cost, effort, wire run, etc. Choice of one of two wires on the back of the ignition switch.

[Be Free]

The loads carried by that switch are minimal. The instruments are not using more than a couple of hundred milliamps. The same goes for the ignition circuit. It just needs to send a signal to the ECM. The start circuit will only have to energize a relay on the starter for the time the starter is turning over. That is probably the largest load and is still not more than an amp or so.


Why try to second-guess the engineers who knew exactly what those currents were when they designed it. Just put the same switch back in wired the same way.



As far as the "gasoline is explosive" concerns, I've never seen a kill switch like this mounted in an enclosed engine compartment. On an 17' bowrider it's going to be mounted somewhere in an open cockpit. Explosive gas fumes are not going to be an issue with the kill switch.