Waste Spark for Tachometer

[Sevcrist]

I want to use a Tiny-Tach on a Mercury 40 hp 4 stroke EFI motor and when I emailed Tiny-Tach they said that the 2RXL Tiny-Tach should work as long as the motor has a waste spark.<br /><br />Does anybody know if the above mentioned motor has a waste spark?

 

[ED21]

Re: Waste Spark for Tachometer

A waste spark would occur on the exhaust stroke.<br />Most 4 strokes do this. It's easier to design I think.<br />If you rigged a spark tester to a plug & determined TDC of the piston by looking on hole, turn flywheel by hand and if it sparks each time the piston comes up to TDC then it has a waste spark.<br />Not sure if this will work with hand turning flywheel. Be safe & hook all plug leads to spark tester so it can't start.<br />Or call Mercury & ask.