Re: kicker running light.
The tach wire is a 'pulsed" signal -- not steady state DC. That said, an indicator from Radio Shack may work on that circuit. It won't be 12 volts however. Probably more in the 3 - 5 volt range. Since that signal is also a :"reference" signal rather than a "driving" signal the regulator circuitry may not like having a load placed on it. Tiny Tach makes a very small tach that has the sense wire simply wrapped around a spark plug wire. Some of them even have an hour meter built in which does run only when the engine is actually running. If the engine has an oil pressure switch you might look into using it as a trigger. However, depending on how sophisticated the engine management is on that engine, that circuit my be a 5 volt "reference" as well and hooking anything to it may upset the system. If it is a 12 volt system, the next thing to check would be if the switch closes with oil pressure or opens with oil pressure. If it closes with oil pressure then you simply need a 12 volt feed to an indicator with the ground for indicator going to the oil pressure switch. Engine starts, you have oil pressure, swtich closes and light comes on. Again, that won't work if the oil pressure "sender" is a resistive element which would feed an oil pressure gauge. Lastly, a low pressure switch in the tell tale line would work. It would need to hold the circuit closed down to 3-5 psi. Upper end is not an issue.
