Twin outboards will crank but not start unless both keyswitches in on position

[fishlips]

Just had a cobia tower installed on my 2005 282 Sailfish with twin 250 4-stroke outboards. Tower has steering wheel, control binn twin, and a deadman switch. There's no key switch in the tower only a deadman switch. Since the outboards are 2005 Yamaha's (800 hrs) had to use mechanical vs digital controls to the tower station. Yamaha dual station selector unit, with 2 dual station unit - throttle and 2 dual station unit - shift installed. All this work done by an authorized Yamaha dealer / shop at the marina. Post-modification, the engines would crank but not start. Only if both main helm station ignition switches were placed in on position would either engine crank over. After conferring with Yamaha techs, they ordered a replacement key switch panel assembly for the main (original) helm station - some concern that a diode may have blown during tie-in of the new deadman switch or the diode just coincidently failed (old age). No different results after replacing key switch panel. Disconnected the tower deadman switch from the ignition ckt and still no change...either engine only will start if both engine key switches are in on position. Marina techs and Yamaha techs apparently stumped. Trying to tell me that this might be an unfixable issue and attempting to review wiring diagrams and Yamaha tech bulletins to tell me why it's that way. I don't want to have to deal with this workaround, but more importantly don't like the idea of what happens if I were to have one engine failure while out on the water...particularly if an electrical problem and I don't want to have to leave the problem engine's ignition on to be able to run back to the dock on the good engine. Any help or suggestions would be much appreciated.

 

[seasick]

Obviously something is wired incorrectly. I am sure that statement doesn't help.

Although I have never worked on a dual station setup, the first place I would look if the wiring and harnesses for the station select switch.
I can understand how motors could crank but not start.
Maybe this diagram will help (assuming you or the tech is up to snuff on electrical schematics.)

 

[seasick]

There are two threads posted for this topic, one in the General Discussion category and one in the Tips, Modifications and Electronics. That can be confusing since responses may not end up where you think thay would be.

 

[Harrysea]

I have a second station topside on my Marlin. Motors will only start/run if the keys at the main helm are turned to the run position. This makes sense to me as I do not have engine performance monitoring gauges at the tower helm and would not be able to get warning alarms if the main helm instrumentation was not activated.

 

[SkunkBoat]

fwiw my brand new twins only have one key