I got a 2016 mercury 115 hp 4 stroke, trying to hook up a tachometer but every diagram I looked, it said "grey" wire color for the sender...there is no grey wire color within the 8 wires. Please help.
See if that loom plugs into or is spliced to another closer to the motor. Sometimes boat manf's extend the engine harness to the dash, combining it with their own in house harness.