Refer: Silicon Chip Magazine November 2009

Avoid unnecessary noise and vibration in twin-engine boats. For optimum performance, both motors should run at exactly the same RPM. You could tune the engine speeds using the tacho for each engine, but it’s impossible to get it accurate as the tacho itself has an error of up to 5%. The Engine Speed Equaliser Kit takes the tacho signals from each motor and displays the output on a meter that is centred when both motors are running at the same RPM. When there’s a mismatch, the meter shows which motor is running faster and by how much. You simply adjust the throttles to suit. Short form kit only, requires moving coil panel meter Cat No. QP-5010.

12VDC
PCB and specified components