Tech Wiki

How to Add a Secondary Starting Switch in the Engine Box

By Mark Elkin, Yorkshire Rose #133


When it comes to engine maintenance, I "single hand" a lot. I find it awkward, to say the least, to climb on the engine to get to the cockpit to fire the glow plugs and/or starter. My solution was simple: add another switch mounted in the engine compartment. I picked up a marine grade SPDT (mom-off-mom) at West Marine. Attached a couple wires (see the diagram) and I was off and running ....... ahem, make that "off and starting".

Important, make sure the switch can handle the amperage for this application. The starter solenoid is easily within the switch capacity. But directly powering the glow plugs would fry switch I used. Fortunately, this toggle switch can handle the Glow Plug Solenoid if that is installed. If not, you can alternately use 2 push button switches, same as up in the cockpit. Finally, make sure you use adequately sized wire: 16 gauge if just using solenoids, 10 gauge for directly powering the glow plugs.

SecondaryStarterSwitch-schematic.jpg SecondaryStarterSwitch-final.jpg

Some notes:

  1. The Blue Sea #4154 (mom on / off / mom on) switch (@ West Marine, elsewhere) is rated 15a @ 12v. Glow plugs are rated @ 6a each. The Cole-Hersee #M-485 BP marine HD push-button switch (@ Defender) is rated 35a @ 12v.
  2. Wired per the diagram, the fuel lift pump isn't powered (and the alternator field won't excite as well) unless the key switch is left on (and alarm sounding,) so another toggle switch could be added if you want to run the pump / bleed the diesel lines. Then you can stop the diesel from below (w/ the stop lever) and not have to climb out to kill the alarm.
  3. Also, the switches need to be within 7" of the power source (e.g., solenoid terminal) or properly fused (for your lightest wire gauge) -- or the wire run be less than 40 inches long and placed inside a conduit or protective casing (ABYC.) -- KWKloeber 1 December 2016