Hobbs meter

It makes a ton of noise once it's started!  ?

Good one, Tyler!

Typically, A mechanical Hobbs is activated by an Oil Pressure Switch.
Once the engine starts and the Oil Pressure is >10psi, the Hobbs will run.
When the engine stops and the Oil Pressure drops below 10psi, the Hobbs stops, 
and with a little creative wiring, a flashing Low Oil Pressure lamp can be activated.
This can give you an immediate heads up of the impending doom.
Two for One!

Bill,

Thanks for the reply. I'm so new to the Rotax engine that I'm almost embarrassed to ask questions. I can't look at my engines yet because they won't be delivered for another couple of weeks. Doesn't the 912iS come with an oil pressure switch already installed? I'm using Dynon instruments (HDX1100 and EMS-221) to monitor the actual oil pressure so for me the switch would only activate the Hobbs meter.

Bill,

No need to reply, I found the answer about an installed oil pressure switch on the forum.

Thanks again,

Brian

The 912is has an Oil Pressure Sender that reports on the CAN Buss to the Dynon.
The Dynon has an internal Hobbs based on either Oil Pressure or RPM or Both.
If the Dynon ever loses its mind, the Hobbs Hours will be Gone.  
It is admittedly possible to recover these numbers from the ECU.
In the rare event that Oil Pressure ever disappears, you have but a few seconds to react before the engine is trashed.
A Red Light Flashing in your face will get a response much quicker than the Dynon reporting Low Oil Pressure from the Engine, you interpreting the Fault and then reacting to the Fault.

A dedicated Oil Fault light and a Mechanical Hobbs are omitted in most installations but are endorsed by others.
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The Oil Switch is OFF when you want the Hobbs to be Running(ON).
The wiring is relatively simple but not obvious.

I also find it a useful indication that I once again left the Master Switch ON.