Yamaha V6 Excel XG 1988 - Weird Buzzer Alarm

[Woodeneye]

Hi all, I'm hoping the collective wisdom in here can give me a few suggestions on how to diagnose & fix a issue with the above. At the dock last weekend on start up I got a buzzer alarm. What's weird is that it started and ran fine with no alarms the day before on the muffs. The VRO is disconnected and I premix, so it can't be the oil alarm. The fuel tank has no sender, so low fuel has never been a issue before. The alarm sounded continuously right away so it couldn't be a overheat issue? Could it? Water pump seemed to be working just fine, nothing running hot....however..... I did notice the choke toggle "stick" a little (as in it didn't flick back to off  straight away as usual) and the ignition action was also a little "stiff". Also, my deadmans lanyard has never worked, since I've had the boat (I know, I know, get it fixed). Could this be causing problems? I'm guessing the Ignition/choke switch is original, its one where the ignition, choke toggle and deadmans are all arrayed vertically one under the other on the same panel roughy 4" x 6"

Any way i can test the ignition/choke switch?  Or just swap it out? Appreciate any input. Thanks in advance.

[Capt. Bob]

Tough one.

I have a manual for this year at home and I'll look at the warnings. I don't believe there is any kind of "low fuel" warning other than the motor quits running, rather a low fuel pressure. All your fuel filters clean? Might be that or...
Sounds like a low oil alarm but you don't use the oil tank(s), still.....................
Are you sure you disconnected everything?

[fitz73222]

Most engines of the era have some kind of warning module in between the temp sensor and low oil sensor that closes to ground and causes the horn to sound. I would suspect a bad warning module or your temp switch in the cylinder head is bad. You could disconnect the warning module but then you lose the audible overheat protection.

[Woodeneye]

Tough one.

I have a manual for this year at home and I'll look at the warnings. I don't believe there is any kind of "low fuel" warning other than the motor quits running, rather a low fuel pressure. All your fuel filters clean? Might be that or...
Sounds like a low oil alarm but you don't use the oil tank(s), still.....................
Are you sure you disconnected everything?

Thanks i'd appreciate you looking. Yep I'm sure the VRO has been disconnected properly. Its been operating fine for some time. I will have another look at the fuel filters.

So no one suspects a bad ignition switch?

Cheers

[Woodeneye]

Most engines of the era have some kind of warning module in between the temp sensor and low oil sensor that closes to ground and causes the horn to sound. I would suspect a bad warning module or your temp switch in the cylinder head is bad. You could disconnect the warning module but then you lose the audible overheat protection.

Thanks I'll have a scratch around.

[Capt. Bob]

OK Wood.

From what I can see in the manual, the buzzer is activated in 3 manners.
1: Low oil in tank
2: "Over revving" of engine
3: Overheating

Since you seem to have eliminated (by your posts) the "low oil tank" and it appears not to be an over rev condition, that leaves overheating which is triggered by a thermal switch activated by excessive heat and when closed, grounds the buzzer circuit (black ground/pink buzzer). You may want to check these switches first. Continuity between the black and pink wire on the switch would indicate a fault at start, thus activating the buzzer. Two switches, one for each bank.

Do you have a multi-function gauge with tach and warning lights?

[Woodeneye]

OK Wood.

From what I can see in the manual, the buzzer is activated in 3 manners.
1: Low oil in tank
2: "Over revving" of engine
3: Overheating

Since you seem to have eliminated (by your posts) the "low oil tank" and it appears not to be an over rev condition, that leaves overheating which is triggered by a thermal switch activated by excessive heat and when closed, grounds the buzzer circuit (black ground/pink buzzer). You may want to check these switches first. Continuity between the black and pink wire on the switch would indicate a fault at start, thus activating the buzzer. Two switches, one for each bank.

Do you have a multi-function gauge with tach and warning lights?

All right Capt Bob! great stuff....I do  the have Yamaha digital multi function gauges. I was playing around with the boat just this afternoon and I noticed a bar flashing over the oil can icon. when the buzzer went off. So in the absence of a manual or any info on the WWW I'm assuming this is a oil alarm. What is weird about this is that the VRO has been disconnected for an age. It has never alarmed before. Are there any circumstances where it would randomly start alarming again?  (or would this flash anyway when the VRO is disconnected??)

I ran it for a  while this afternoon and the cooling system was going strong and the heads only got warm to the touch. I also pulled the PRV and the thermostats and all looked just fine.
As an aside I noticed the Deadmans lanyard switch has had a one of its wires cut, white in colour (earth?), by the previous owner, which may explain why it doesn't work.

[Capt. Bob]

I do  the have Yamaha digital multi function gauges. I was playing around with the boat just this afternoon and I noticed a bar flashing over the oil can icon. when the buzzer went off. So in the absence of a manual or any info on the WWW I'm assuming this is a oil alarm. What is weird about this is that the VRO has been disconnected for an age. It has never alarmed before. Are there any circumstances where it would randomly start alarming again?  (or would this flash anyway when the VRO is disconnected??)

If the oil injection system was functional, that would indicate that the engine was overheating for some reason so.......
First, if just the light (triangle shaped?) above the "oil can"(in the lower middle of the display) comes on, it indicates that the "reserve tank" (mounted away from the engine) oil level is too low to transfer to the "main tank"(under the cowling). One needs to add oil to this tank.
When that light is coupled with a buzzing alarm, it indicates a power head overheat condition.

Your oil system has been disabled so....
Are the reserve and main tanks and the float switches inside each still in place?
If so, a switch now may be sending a signal to the oil module itself (this is the module Fitz was addressing earlier).
This module sends the signal to both the buzzer and the multi-function display and could also be your trouble point.
A manual with a wiring diagram would go a long way in helping sort it out.

As an aside I noticed the Deadmans lanyard switch has had a one of its wires cut, white in colour (earth?), by the previous owner, which may explain why it doesn't work.

The switch acts as a grounding device to kill the engine (ignition). Depressed with the clip and lanyard, and then attached to the operator, it might save your bacon if you fall overboard. That stated, it needs to be depressed(clip in place)  when you crank the engine in order for the switch to function. . You can start the engine with the clip removed on OMC units but I never tried on my Yamaha. The white wire you see would allow the ground circuit to be completed after the engine starts and then the clip was removed. Maybe on the Yamaha, that white wire needs to be disabled for it to start.  You could try reconnecting the wire and see if the motor starts without the clip(I'm thinking it might) but you will definitely need to reattach it to the switch if you plan on using the kill switch function.

Good luck

[Woodeneye]

Thanks for your assistance thus far. The oil tank and reserve are no longer installed. There are just a couple of vacant wire harnesses where the the tanks once were.

Seeing how the tanks and float switches are no longer installed and thus disconnected is it possible the no oil alarm would still sound and get a display warning on the multifunction gauge as well?

[Capt. Bob]

Thanks for your assistance thus far.

Our pleasure.
 

The oil tank and reserve are no longer installed. There are just a couple of vacant wire harnesses where the the tanks once were.

Ah, the plot thickens. :o

Seeing how the tanks and float switches are no longer installed and thus disconnected is it possible the no oil alarm would still sound and get a display warning on the multifunction gauge as well?

Yes, because of the "oil sensor module" that Fitz spoke to in his post. This module activates both the light and buzzer from signals (grounding) of the float (or thermal, I believe) switches themselves. Since the float (oil) switches are gone I'd venture to say that the module now becomes a main suspect. I'd guess it has not been removed or still (depending on year) may even be located within the CDI unit itself so.....

Locating the module is the next step. A couple of pics of the engine would help to see if we can find it in the service manual.
Just a thought.

[fitz73222]

Apples and Oranges but I've replaced them on all my older Mercs for the same reason. My hot horns would start to randomly chirp and then start sounding steadily and then stop and start again for no reason after completely checking all systems for oil and temp issues without any findings including replacing the keyswitches. The new modules fixed the problem. Both of my twin 115's were doing it within a month or so of one another. Mine were separate modules from the ignition CDI unit so hopefully that is the case for your Yamaha.

[Woodeneye]

Thanks for your assistance thus far.

Our pleasure.
 

The oil tank and reserve are no longer installed. There are just a couple of vacant wire harnesses where the the tanks once were.

Ah, the plot thickens. :o

Seeing how the tanks and float switches are no longer installed and thus disconnected is it possible the no oil alarm would still sound and get a display warning on the multifunction gauge as well?

Yes, because of the "oil sensor module" that Fitz spoke to in his post. This module activates both the light and buzzer from signals (grounding) of the float (or thermal, I believe) switches themselves. Since the float (oil) switches are gone I'd venture to say that the module now becomes a main suspect. I'd guess it has not been removed or still (depending on year) may even be located within the CDI unit itself so.....

Locating the module is the next step. A couple of pics of the engine would help to see if we can find it in the service manual.
Just a thought.

This electrics caper is all voodoo to me...... I shall attempt to post photos/and or locate a module.

[Woodeneye]

Apples and Oranges but I've replaced them on all my older Mercs for the same reason. My hot horns would start to randomly chirp and then start sounding steadily and then stop and start again for no reason after completely checking all systems for oil and temp issues without any findings including replacing the keyswitches. The new modules fixed the problem. Both of my twin 115's were doing it within a month or so of one another. Mine were separate modules from the ignition CDI unit so hopefully that is the case for your Yamaha.

When you say "modules" are you referring to the buzzer/alarm unit itself?? Cuz that is separate from the ignition switch panel on mine and easily accessed.

[fitz73222]

Apples and Oranges but I've replaced them on all my older Mercs for the same reason. My hot horns would start to randomly chirp and then start sounding steadily and then stop and start again for no reason after completely checking all systems for oil and temp issues without any findings including replacing the keyswitches. The new modules fixed the problem. Both of my twin 115's were doing it within a month or so of one another. Mine were separate modules from the ignition CDI unit so hopefully that is the case for your Yamaha.

When you say "modules" are you referring to the buzzer/alarm unit itself?? Cuz that is separate from the ignition switch panel on mine and easily accessed.

This would be under the engine cowling and may be nothing more than a small black box with some wires coming out of it. Locate the temp switch wire from the cylinder heads and see where that wire goes. It should connect to a module. This has nothing to do with the dash, switch panel or actual horn/buzzer.

[futch13]

Look under cowling either by missing oil reservoir or by the ECU, there should be a grey toggle switch.  This is contained in your oil module.  If it is separate, try disconnecting it.  If it is on the ECU, you will need a new/used ECU i'm sorry to say.