Twin OX66's Shut one off, the other shuts off!!

[GNAVA CHARTERS]

Hi guys, new to the board, glad to be here! I have been pulling the hair out of my head...whats left of it anyway. Twin 1999 ox66 225 fuel injected...properly maintained, 1500 easy hours. Last week, went for a cruise, stopped to get ice, both motors would not start...checked everything. 30 minutes later, they both started, ran all day, came back to dock, shut them down and went to restart. Nothing. Started no problem next day....same thing. When they were running, I shut one off, the other then shut off immediately. Some different tones coming from the ign switch...sort of a higher pitched tone when turning over. Changed everything imaginable, checked everything....think it could possibly be the key switch?

She will start cold (both motors) run all day
Shut it down, they will not start- and give a different sounding alarm
Shut one engine off when idling, the other shuts off immediately

Got me good on this one, thoughts? Thanks guys!

[99yam40]

Might be something with the duel switch system or kill switch set up.
does it have one kill switch that kills both motors when pulled?

[GNAVA CHARTERS]

Yes, the lanyard kills both at the same time....I am about to replace the whole unit...$300.

[99yam40]

from what I have read when one motor goes into RPM reduction that duel set up also limits both motors RPM and sounds the buzzer and if on dies the buzzer will sound, but should not sut the other one down.

maybe a diode or something shorted could cause this, but you need to wait for Rodbolt to give better information on a possible repair

[rodbolt17]

we can rule out the DES switch.
you may have an issue with the stop lanyard or a ground issue.
if you get a tone when cranking it indicates a start and stop signal at the same time.
unplug the stop lanyard switch and retest.

[GNAVA CHARTERS]

Turns out it was a faulty dual key switch....about $300 and the problem is fixed....what a strange day...thanks guys!!!