Please Help: 7 Years of Buzzer Issues on 1996 Yamaha's 150's

[rodbolt17]

just the gray bullet connector.
DO NOTunplug the white square connector.
wont hurt but it wont help either.

ok
quick lesson.
how the circuit works.
from the keyswitch,yellow key on 12V goes from the switch to the alarm horn.
from the horn its pink to the temp SWITCHS.
black from the switch is always ground.
the gray splices into the pink,typically a few inchs back from the stbd switch.
if that switch closes you now have CURRENT flow, sets the alarm audible.
the now complete circuit on the gray wire sets the visual.
the complete path to ground also sets RPM reduction.
however if the tach or wire path on the gray wire goes to ground the circuit simply sees a ground path just as if a temp SWITCH had closed.
trust me if that much cast aluminium was over 190* it takes way more than 30 seconds to cool down.
switch should close at about 190* and set the alarms.
alarms will clear at about 160* when the switch opens.
its NOT a sensor its a on/off switch.
anyother readings indicate a defective switch.
remember,ohms is simply a measure or electrical resistance,open being infinite and closed being zero.
voltage is simply a measure of electrical pressure.
current flows and actuates devices.

[99yam40]

So the disconnecting of grey connector is just to troubleshoot, to see if that will stop the alarm from going off not just get rid of the visual indicator?

Hopefully you have bad tachs or grey wires and this solves your problem.



What the real kicker is, is that he can pull the switches loose from heads and let them hang and the alarm does not go off. So It would have to be bad wire to switches on both motors.

[rodbolt17]

for oil the pink is grounded by the oil control module and the visual is set via the green/red wire in the trim/oil harness.
same alarm tone different visuals.
low battery voltage can also set the alarm.
but as the gray ties into the pink anything on the gray that takes pink to ground will set the alarm.
there is also a dual engine switch that can malfunction due the EMI from spark plug caps or wires.
sometimes it does not take a solid ground to trigger a solid state device.

dual engine switch is located behind the key switch panal.
its purpose is if one engine goes into RPM reduction it takes the other engine down as well.
it can be disabled for testing.

[Doc of the Bay]

So Rodbolt, to sum it up, I disconnect the gray bullet connectors on both engines and go run it and see if the buzzers go off or not, correct? And if the buzzers go off with the gray bullet connectors disconnected, does this indicate an issue with the wiring instead of the thermo switches? Doc

[99yam40]

If you disconnect the grey wires and alarms still goes off, that should eliminate the grey wire and tach from problem so you can focus on something else.

I am going toward the EMI, but that is just because I had never heard of this before and this whole thing has me puzzled anyway.

Wires could be picking up the EMI and when disconnecting switches from head just the moving of the wires changed things. Just a thought.

Lots of troubleshooting still needs to be done

[Doc of the Bay]

Thanks 99. I will try to get out this weekend and get some more #'s on the temps of the heads and run the test Rodbolt suggested with the gray bullet connectors disconnected. I will let you all know, Doc

[99yam40]

there is also a dual engine switch that can malfunction due the EMI from spark plug caps or wires.
sometimes it does not take a solid ground to trigger a solid state device.
.

Just curious, is the grey wire tied to this duel engine switch?
Or is it a different wire or set of wires?

[Doc of the Bay]

Hello guys. Well, I didn't get a chance to hit the water this weekend. Too much going on. And this coming weekend I am in a tournament so I will try to keep it under 3200 and avoid a buzzer. The following week or weekend I should be able to hit the bay and do some more troubleshooting. Thanks again guys for all the troubleshooting tips. Talk back in a few days, Doc

[Doc of the Bay]

Hello again guys. I am hopeful that I will get a chance this weekend to run more tests on my buzzer issues. This past weekend the bay was kicking at a steady 3-4. Will get back soon with results of recommended tests. Thanks again, Doc

[zenoahphobic]

The problem needs another brain storm.
Faults are usually singular and in principal simple.
Seeing this problem has been in existence for many years you could discount deteriation from corrosion and wear and tear.
This situation logically has its cause Common to both engines and had occured some time ago.
Everything that is "common" requires lateral thinking. Not only componentry but processes undertaken on both engines at the same time. That is Q.A from manufacture to all servicing done simultaneously on both engines.

I would look at what happens around 3000+ rpm, as there are a few things. Is this where max ignition advance occurs (or indeed goes too far because it has not been set correctly?. Secondly has the boat got dual batteries and VSR and is this where it switches to Aux batt because alternator output ceases to rise? Or indeed does proper voltage regulation occur? Thirdly what equipment might turn on or off when boat reaches this speed?
The point I'm making is that if the wiring was incorrectly connected (some time ago), or equipment (even guages) may go OK for most time but react when Voltage rises or spikes/drops, the system may go into fault mode (turns on buzzer). When 'fault" occurs, does or should it be reset by ignition off or by itself may give a clue. I'd check supply voltage everywhere (where it should be), and check statically what happens when throttle lever is moving to this point (throttle position determines RPM). I would also look suspiciously at things (instruments etc.) where Starting battery and Aux battery provide supply together, including earth paths (for "Brake light blinking when turning on trailer syndrome" no doubt we are all aware of).
I would also check physical loads such as overpropping, trim, trim tabs etc. as there could be loads affecting water intake or circulation cavitation. Don't assume water pressure means there is flow!
Just a left field thought.