85hp Chrysler 1969

My boat at the dashboard electric wise is not quite the same as it shows in the manual. My dash has a fuel tank guage, choke, and speedometer. The manual shows the tach wire as being white and this has to be connected on the engine wiring block the same. So here is my problem. There is one wire that is a ground from the speedometer and goes back to the enging block and connects where it is suppose to. The engine side has a white wire comming out of the CD unit but no wire is connected from the dash side on the wiring block. The manual says two wires come off the tach at the dashboard and straight back to the engine block wiring block. Like i said the ground is there and of course its white, the wrong color. I now have a yellow wire which is an additional wire not connected at the engine or the dash. The terminal size of the wire at the dash doesnt fit over the bolt of the speedometer. Now, The engine turns over, so that much is correct. I checked the top posts of the coil to see if juice was comming in with a 12volt meter. It was not. Well no surprise, there is no wire from the dash going to engine wiring block. My question is, do i run this wire from the other terminal on the speedometer. this dash does not have a tachometer. I thought the tachometer measured rpms, this guage say 0-55 on it. bottom line is there's no juice to the coil. This does have a cd unit on it. blue and white wires run to the coil, and two blue and whites run over to the engine wiring block. Any ideas?. Could I run that wire off the hot on the ignition key switch.