Voltage to tach at 0 volts.<br /><br />This is actually a two part stupid human trick, but the first part is really a stretch for this forum, because the motor was on the muffs... not really what I consider boating. The second part fully belongs here, because the boat was in the water, floating, and under power... now this I consider boating.<br /><br />The tach is a teleflex, and has terminals for the send wire, positive for lights, ground (I assumed for lights), and ignition.<br /><br />The first part was when I had the tach installed, and hooked up. I started her up on the muffs. Idling nicely... at 0 rpm 
Checked the send wire... no problem. Checked the ignition wire... no problem. Checked the other wires... PROBLEM I didn't hook up the pos+neg wires to the battery... I had assumed that the negative wire was only for the light. Hooked up the neg wire to the battery, and my idle speed immediately jumped from 0 rpm to about 1100 rpm <br /><br />The second part of my stupid human trick was on the maiden voyage. I putted away from the launch with the motor purring away at a nice healthy 0 rpm. I gave it some gas, and it came up on plane easily at a nice 0 rpm. Let her accelerate, and she was moving along nicely with the motor whizzing away at a healthy 0 rpm. I also cruised along for a bit... at 0 rpm.<br />As a sidenote, but related, I still need a choke switch (on order). So for the maiden voyage, I had the ignition switch out of the controls, and did the old touch-two-wires-together-to-activate-the-choke-switch trick. In order for the tach to work, the ignition wire for the tach needs to be connected to the ignition in the controls, which also gets connected to the choke switch. The plan is to solder that on when I install the new choke switch.<br />But for now, I twisted the tach ignition wire to the ignition wire for the choke... but not for the maiden voyage. Stupid me didn't realize this was the problem until I was laying in bed, troubleshooting in my head, and thought about that ignigion wire, not hooked up were it was supposed to be.
Checked the send wire... no problem. Checked the ignition wire... no problem. Checked the other wires... PROBLEM I didn't hook up the pos+neg wires to the battery... I had assumed that the negative wire was only for the light. Hooked up the neg wire to the battery, and my idle speed immediately jumped from 0 rpm to about 1100 rpm <br /><br />The second part of my stupid human trick was on the maiden voyage. I putted away from the launch with the motor purring away at a nice healthy 0 rpm. I gave it some gas, and it came up on plane easily at a nice 0 rpm. Let her accelerate, and she was moving along nicely with the motor whizzing away at a healthy 0 rpm. I also cruised along for a bit... at 0 rpm.<br />As a sidenote, but related, I still need a choke switch (on order). So for the maiden voyage, I had the ignition switch out of the controls, and did the old touch-two-wires-together-to-activate-the-choke-switch trick. In order for the tach to work, the ignition wire for the tach needs to be connected to the ignition in the controls, which also gets connected to the choke switch. The plan is to solder that on when I install the new choke switch.<br />But for now, I twisted the tach ignition wire to the ignition wire for the choke... but not for the maiden voyage. Stupid me didn't realize this was the problem until I was laying in bed, troubleshooting in my head, and thought about that ignigion wire, not hooked up were it was supposed to be.