Marine tachometer installation:
Diamete: Open a 85mm (3 3/8") and 55mm( 2 3/16) depth hole to put the boat tachometer into it, easy to install.
Waterproof: The gps speedometer car with TFT screen, marine speedometer is IP67 waterproof and anti-fogging protection.
NOTE: Because the actual engine configuration situation will be more complex, we only do part of the engine cylinder number numerical recommendation, so if you do not see the numerical recommendation for your engine cylinder number in the user manual, and do not know the gear number of the engine, we will recommend the appropriate speed ratio value for you.