Contact TinyTach customer support so that you get the exact model that you need. If you are going to mount the tach at the helm, be sure to have the extra wire installed with the order.
I just want it for testing, not for all the time usage. I want to be sure I am spinning the motor at its correct RPM. i only have 2-3 loading profiles, so it would probably be a once in a lifetime thing. thanks, Rick