Joe92GT

Normally, when you turn a key do all the gauges come on no matter which key, or only that engine's set?

I'm guessing they have two diodes in the circuit somewhere so that with either engine running, all the gauges are powered on. The problem may be with the diode(s), or before them.

Thunderstruck

Remember that if the ignition is somehow connected to a continuous 12V source like the parallel switch or the trim, the motor will not shut off (nor will the gauges) with either key. Must be stbd ignition (purple) touching port ignition purple to cause the motor to be able to shut off with the other motor's key.

stevesxm

this is a very good point. when i rewired my boat, i did it such that only the the instruments for THAT motor were lit with THAT switch. because of the injection, i din't want any possibility of one sensor array " talking to the other " through a common reference signal. IF the above post is correct and that somehow the dash panel is lit from either key then there would have to be a diode in the system somewhere, which, if bad would do this as he mentions.

if this were mine to diagnose, i would start the motors with both ignition switches hanging out of the dash by their wires. then first, i would yank the lanyard on the one that won't shut off. if it shuts off then the problem is in the dash. if it DOESN'T shut off then the problem is a shorted wire in the loom beyond the lanyard ... in the bulkhead or engine compartment.

then i would put the lanyard back and restart and turn the ' bad" switch off. then i would test the poles on the switch ( assuming the motor still running) and see if the wire that was supposed to be dead w/ switch off is still alive. if yes, then a short in the loom ( or the diode issue) if no then short downstream again.

then i would remove ANY ancillary wires from that switch that are NOT engine related... stereos/power feeds to other systems etc... then repeat the test... if the relevant pole goes dead then its being back fed thru one of those systems. if still alive then a short in the loom as before.

the battery switches sound like mine... so if thats the case then a bad switch won't cause this.... you can't backfeed the ignition thru the master bat cable... UNLESS there are alternator feeds to it as well which , while i have seen this, is uncommon.

when doing the diagnosis there is a notion to disconnect the bat while the motor is running to see if it shuts off... don't. it will continue running on the alt and ( even tho i don't know why) it has been published endlessly that this is bad for the alt.

also... one more thing to try... disconnect the alt wires from the GOOD motor and repeat the test... if the bad motor shuts shuts off normally then it is being back fed from there somehow.
if not ... well you don't know much of anything helpful but it one more piece of data to use. then try it on the bad motor ... same deal.

then put all the results of these tests in a flow chart on a piece of paper and look at it. the answer will be right there.

bford1

Wow guys. Thanks for all the awesome repsonses. Sounds like I have my work cut out for me and I may be in over my head here.

A couple of things I noted when reading the responses.

First, neither ignition switch seems to be the "bad" one. Both act the same way. The Starboard won't shut off without the port off and the port won't shut off without the starboard off. I don't know if that tells you anything or not.

I am going to check the purple wires on the ignition keys first and see if they are touching. Then I will try the lanyards to see if they will kill either motor. I will try to figure out whether the issue is behind the dash first and go from there.

Thanks again guys. Great info. I jsut wish i wasn't such an idiot when it came to electrical system gremlins.

Thunderstruck

You are on the right track. If you can not find the problem, please let us know whether ALL the dash powered up with one key or just the gauges for the associated motor power up with the key BEFORE the problem started if you can remember. Please let us know what is the case now with the gauges, if one key turns on all the gauges now or not. Also, carefully document on OSO what you do to troubleshoot so we can stay in the loop.

phil0460

you dont by chance have one of the first smartcraft systems??