On the back of your existing key switch will be a yellow/red wire that fires the start solenoid when you roll the key to Start.
Pull power from a switched circuit (purple) into whatever push button you want to use. Splice the switch's output into the yellow/red circuit on the back of your key switch. That will fire the solenoid exactly the same way the key switch does.
Be sure to wire it in parallel or you'll need to use both to start !
The Cole Hersee pushbuttons (M490, M626) work well for that and you can get them with a boot.
There's not much current going through it so you can use just about anything as long as it's robust enough to be on a boat.
Your start-in-gear protection and lanyard switch won't see any difference.
A lot of OEMs (esp Sea Ray) mount the key switch out of the weather and use a start/stop button on the dash (or the control) instead on their SmartCraft boats.
As to the nut on the switch... sikaflex the threads and the top of the switch body.
If you have a thin (brass, aluminum, uncored glass) dash panel, the inner nut might be threaded too far down the barrel, allowing the outer (trim) nut to bottom out before it tightens against the dash.
Black | Ground | Negative / Neutral Main Return |
Blue-Stripe | Tilt up and or trim out | Tilt and or trim circuits |
Brown | Alternator Charge Light | Generator Terminal or Alternator Auxiliary Terminal to Regulator |
Generator Armature | Generator Armature to Regulator | |
Pumps | Circuit Breaker or Switch to Pumps | |
Brown w/Yellow | Bilge Blowers | Circuit Breaker or Switch to Blower |
Dark Blue | Cabin & Instrument | Circuit Breaker or Switch to Lights |
Green or Green w/Yellow Stripe | Bonding System | Grounding Wires (if insulated) |
Green Stripe | Tilt down and/or trim in | Tilt and or trim circuits |
Grey | Navigation Lights | Circuit Breaker or Switch to Lights |
Tachometer | Tachometer Sender to Gauge | |
Lt. Blue | Oil Pressure | Oil Pressure Sender to Gauge |
Orange | Accessory Feed | Ammeter to Alternator or Generator |
Common Feed | Distribution Panel to Accessory Switch | |
Feed | Accessory Circuit Breakers or Switches | |
Pink | Fuel Gauge | Fuel Gauge Sender to Gauge |
Purple | Ignition | Ignition Switch to Coil & Electrical Instrument |
Instrument Feed | Distribution Panel Electrical Instruments | |
Red | Instrument Feed | Distribution Panel to Electrical Instruments |
Power Feeds | Positive Main Power (particularly un-fused) | |
Tan | Water temperature | Water temperature sender to gauge |
Yellow | Generator Field | Generator to Regulator Field Terminal |
Ground | Negative / Neutral Main Return | |
Yellow w/Red | Starting Circuit | Starting Switch to Solenoid |
Yes, the key will just be a switch that turns on the main power relay and wakes up the ECM.
The button just runs the starter once everything else is ready to start.
Obviously you wouldn't want to put it somewhere it might accidentally get pressed while the engine's running.
Missile switches are great for that but you have to like the look of them
What engine have you got ?
Mercury inboard