I bought a used 17" bass boat with a 115 evinrude motor. I need to change the prop on it. It's got a 12-1/2 x 21 sst. My hole shot sucks really bad. To figure out what prop I need, I got to fix my tachometer so I can see how my rpm I'm turning wide open. Does anybody have a clue on how to wire a boat tach. Mine doesn't work and I have no idea which wires to check on the motor. Somewhere between the tach and the motor they change colors so I can't trace them. Any help would be appreciated.

Mine was simple to hook up. + wire to a spark plug, - to the ground. It wasnt that simple, but thats the jist of it

whats the year of the engine?? and what tach do you have?? does the engine have a electronic ignition?? if so there should be an electronic box aka CDI or powerpac inside or on the CDI there should be a grey or white wire thats the tach wire, the only real important wires on the tach to get it working is the grey, black and red wires. connect the grey wire of the tach to the tach wire in the outboard connect the red wire to a power source and ground the black wire. I hope this helps it could very well be different with your setup, but thats how it went hooking up a 1999 teleflex tach to my 1994 evinrude motor. good luck

that sounds simple enough, it's 1984 115. I'll take a look at it this weekend.