Re: Hour meter for my big Johnson?
You don't hook to the tach leads. The meter is connected to a switched 12 VDC lead, so that when ignition switch is "ON", the hour meter runs. They don't run faster or slower with engine RPM changes, they just record actual hours the engine has run. They're cheap [<$30]. Go for it.<br /><br />There is a special kind of tach [used on reciprocating engine aircraft] that has an hour meter built into the tach and the recording does vary with RPM of the engine, but this is not available or useable in the marine world.