The resistor needs to be bypassed only when cranking but the EI manufacturer may/may not need it- contact the company. I talked to Sierra a couple of weeks ago about this issue and the tech guy told me that it is needed, so....
The solenoid will have a crank wire and another that goes to the coil, which is the bypass wire. If the coil has another purple wire, the resistor usually goes to the end of the wire and the coil. That should keep the tach and EI happy. If the EI doesn't have the resistor, the wire from the coil can fuse, which is what happened to the boat I called about.