Why is my System Check alarm sounding?

[guy48065]

... But there's no warning light and the motor seems to be running fine.
The alarm tone stops if I keep the motor above 3000 rpm, or at idle.

I thought the warning tone was supposed to accompany the light--but doesn't sound by itself.

2000 40hp Johnson.
Factory harness, no splices or mods.

 

[saltchuckmatt]

Alarm should do two things, an overheat situation or something wrong with the oiling system if you're using the vro. My guess on this one is, is you haven't changed your impeller or looked at it. Probably slightly overheating at low speed and it's good at high.

 

[dingbat]

An alarm that goes away at high RPM would have me looking for an over heat condition or a fuel restriction, ie fuel filter(s)

I get a rouge auditable alarm (no check engine light) every once in a while when running in slop when low on fuel.

So far, nobody has been able to explain how or why the alarm is triggered

 

[guy48065]

If I was overheating just cruising at 1200 rpm, why would the tone (NO light) immediately stop when I pull it back to 800? Or speed up to 3100? This seems counter-intuitive to me that it would be so specific.

 

[guy48065]

...I get a rouge auditable alarm (no check engine light) every once in a while when running in slop when low on fuel.

So far, nobody has been able to explain how or why the alarm is triggered

So you're also getting a mysterious tone-only alarm?

 

[saltchuckmatt]

Who's the poster on this?

 

[dingbat]

If I was overheating just cruising at 1200 rpm, why would the tone (NO light) immediately stop when I pull it back to 800? Or speed up to 3100? This seems counter-intuitive to me that it would be so specific.

No really……could be on a threshold.

Dropping from 1200 to 800 reduces fuel demand thus lowering the vacuum.

On the other hand, the increased rpm could overcome any blockage in the fuel delivery system.

The other possibility is the something in the throttle linkage (throttle lever/cable) is shorting the alarm to ground in those throttle positions.

So you're also getting a mysterious tone-only alarm?

it happens very rarely, but I’ve them.

I wouldn't call it mysterious as I know under what conditions it can happen. I personally think it’s the lose of vacuum (sloshing exposes fuel pickup to air) in my case, but have been told that’s not the case.

Have not pulled the data sheet on the vacuum sensor to see if that is indeed alarm on high and low vacuum

 

[saltchuckmatt]

Solid tone alarm or.....

 

[guy48065]

Solid tone alarm or.....

Continuous.

On my drive home tonight I was thinking about how it's acting strange. At one point during my brief cruise the radio also acted up. It started screaming along with the alarm tone. Volume control had no affect (separate amp), couldn't turn it off. Embarrassing.
Turning off the motor ended the radio issue, but the alarm resumed on restart. I thought it was a separate issue but now I'm sure they're connected.

Next time I'm at my cottage I'm going to search for a bad ground.

 

[saltchuckmatt]

Yeah, you probably have a short.

Shouldn't be to hard to diagnose that one. I call that a blessing in disguise.

 

[guy48065]

SOLVED. Bad tachometer.
Last weekend I verified battery and switched voltage was good & connections tight. I couldn't find any problems with the harness or connectors. I opened every connector on the motor & checked they were clean & tight.

So that left me with the alarm itself.
I found a NIB replacement on eBay and installed it Friday. Fixed.
No more:
Tach stops responding.
Weird rpm readings.
Unexplained alarms with no idiot lights.

This is a Sierra "Lido" analog tach with System Check and i replaced it with same. I hope that wasn't a bad call.

Posting this for the benefit of others, since I haven't read of these symptoms before.

 

[dingbat]

SOLVED. Bad tachometer.
Last weekend I verified battery and switched voltage was good & connections tight. I couldn't find any problems with the harness or connectors. I opened every connector on the motor & checked they were clean & tight.

So that left me with the alarm itself.
I found a NIB replacement on eBay and installed it Friday. Fixed.
No more:
Tach stops responding.
Weird rpm readings.
Unexplained alarms with no idiot lights.

This is a Sierra "Lido" analog tach with System Check and i replaced it with same. I hope that wasn't a bad call.

Posting this for the benefit of others, since I haven't read of these symptoms before.

Might want to check your voltage regulator

Erratic tach readings and weird voltage surges are typical failures of a voltage regulator on the way

 

[Faztbullet]

The original System check tach units are know for problems