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Old 17-08-2019, 20:29   #1
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Yanmar engine starts but power buzzer does not turn off/ no tacho

I can start my Yanmar engine as usual but the power buzzer does not turn off and the tacho does not display revs. If I turn off the power switch the engine continues to run and the buzzer stops but of course the instrument panel is off. I can then turn the power switch back on and press the stop switch and the engine stops as usual, and then I turn off the power switch to stop the buzzer.

Any advice on how to diagnose /fix? Am i causing any damage by running the engine with the instrument panel turned off?

Thanks!
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Old 17-08-2019, 21:02   #2
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Just a hunch, I would look at alternator output.
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Old 17-08-2019, 21:14   #3
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Just a hunch, I would look at alternator output.
Yep ... on my way back to the anchorage to check fan belt etc cheers
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Old 18-08-2019, 00:06   #4
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

I thought you weren’t suppose to turn the switch off until you stopped the engine. .... causes problems.
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Old 18-08-2019, 00:35   #5
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Presumably the idiot lights are OFF (???) i.e. you don't have a low oil pressure or high water temperature alarm or charge light.

What model Yanmar?
Is this happening on one engine only?

Running with the power switch OFF is not going to cause any immediate damage to the engine except that you have shut down the engine alarms which sort of means you are running blind.
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Old 18-08-2019, 03:40   #6
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Originally Posted by Wotname View Post
Presumably the idiot lights are OFF (???) i.e. you don't have a low oil pressure or high water temperature alarm or charge light.

What model Yanmar?
Is this happening on one engine only?

Running with the power switch OFF is not going to cause any immediate damage to the engine except that you have shut down the engine alarms which sort of means you are running blind.
Yes warning lights are off (and never came on apart from usual start up procedure)
4JH5E
Only on one engine - other fine (Lagoon450)

Thanks for the info
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Old 18-08-2019, 08:57   #7
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Check all leads to ignition switch coming in and going out.
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Old 18-08-2019, 08:58   #8
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

I would have immediately checked oil and coolant levels. If they are both fine, you are in a much less worrisome position about the buzzer.
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Old 18-08-2019, 09:03   #9
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Quote:
Originally Posted by NYSail View Post
I thought you weren’t suppose to turn the switch off until you stopped the engine. .... causes problems.
Depending on how the boat is set up, yes , it can blow the alternator.
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Old 18-08-2019, 09:05   #10
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Doesn't the battery light come on? It should light up at every start? If the buzzer stops when you accelerate (even when idling), then the battery may be empty or broken, or the wire from the alternator does not tell the panel that the starter battery is charging, or the Batterie does not tell the alternator.

Here was another thread with a similar problem: the fan of the engine ventilation led to the failure of the fuse between alternator and battery switch or something similar.
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Old 18-08-2019, 09:33   #11
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

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Originally Posted by Cheechako View Post
Depending on how the boat is set up, yes , it can blow the alternator.
I am not sure you are correct. Turning off ignition switch while engine is running will remove field current to the alternator, if an external regulator is used. External regulator gets its power from ignition switch. Removing field excitation should reduce alternator output to nearly zero. If internal regulator there is probably no change in alternator conditions.

Did I miss something?

Of course this assumes a direct connection from alternator to at least one battery at all times. Never heard of a setup where there was a relay in that connection that had to be powered from the ignition switch, but suppose it is possible as a protective measure.

BTW ignition switch usually powers the hour meter also, so if you run engine very long without proper ignition circuit function or leave a functioning ignition on when engine not running your hour meter will be wrong.
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Old 18-08-2019, 10:01   #12
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

What “power buzzer”? My Yanmar has a warning buzzer for any alarm light, normally the low oil pressure alarm sounds when first started until pressure comes up, usually in a few seconds. Could also be due to the (no) charge warning light. If yours keeps sounding, you need to figure out why and fix that.
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Old 18-08-2019, 11:04   #13
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Hi, its not a “power buzzer” its a low oil pressure alarm and could be very serious to the health of the engine. You may have noticed that when the engine is cold and you stop it (with the ignition still on) it takes a few seconds until the buzzer comes on again? This is because the oil is cold and thicker.

Do not continue to run the engine until you have at the very least checked the oil level on the dip stick. If there is plenty of oil, it could be an oil filter problem, change the filter if you have one.
Best case scenario is it could be a faulty oil pressure switch. (Or even the wire for it has come of and is shorting to earth!) You need to get this properly diagnosed BEFORE running the engine again, worst case is serious mechanical damage to the engine.

And NEVER turn of the ignition switch when the engine is running, (unless it is designed with an electric engine stop and specifically tells you in the instructions to do so) it could (and May already have) blown the alternator diodes (which may be the reason the tacho is not working!
Sorry for the bad news.
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Old 18-08-2019, 13:18   #14
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

What model Yanmar? 2GM Tamara get the tach signal from a sensor on the bellhousing that counts teeth on the flywheel!

My guess is that if you indeed have a 2GM engine, the tach and oil pressure warning are loosing electrical connection at one of the connector plugs in the engine harness.

Suggest you trace the wires from the oil pressure sensor into tge harness, and disconnect the connector plugs and clean the connections carefully. Don't worry about the connection, they can only go one way!
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Old 18-08-2019, 15:52   #15
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Re: Yanmar engine starts but power buzzer does not turn off/ no tacho

Your alternator voltage regulator may be kaput, or the brushes on the slip rings in the alternator worn out.

Annoying--but not a biggie--less than a hundred bucks--
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