Yanmars engine alarm

Ed Schenck · Apr 24, 2011

How do you know that the problem is not overheating or low oil pressure? Do you have a lamp test showing all warning lights are good? Even so I would want to use a gauge for both oil and water temp.

Steve Dion · Apr 24, 2011

I had an issue similar to this on my 2GM20F (fresh water cooled) engine. It was the sending unit (front of the engine) that was shorting out. It would periodically chirp or sound at something less that the full sound. I would check that connection to be sure that it is solid.

John T1594 · Apr 25, 2011

Growl

I had a similar issue with the 2QM15 on my H30. A blown diode in the alternator will cause the charge lamp to glow dimly and the alarm to growl when the engine is running. However, the alarm buzzer will growl and the charge lamp will flicker but not go out as engine speed is increased. The buzzer seems to growl sometimes when idling below 1,000 RPM especially when the battery is low. The 2QM15 had no engine kill cable and you stopped the engine by reducing the throttle.

Bill Roosa · Apr 25, 2011

99.44% of all boat electrical problems are corroded connections.
The buzzer is set off by any of the engine sensors grounding or the diodes in the back of the engine panel shorting out. To test the sensors try this:

Oil pressure sensor:
The unit on the engine is open when the engine is off and closed when the engine is running and has oil pressure. Pull the wire off the sensor at the engine and measure the resistance between its terminal and the engine with the engine off. You should get infinite resistance. Start the engine and re-measure; you should get 0 ohms resistance. If you get anything over 5 ohms when oil pressure is present then the sensor is bad. To test for oil pressure just pull the sensor and start the motor oil should come squirting out the hole.

Immediately stop the engine as you are not getting oil pressure to the bearings with the sensor out!!!!!!

Water temp sensor:
Pull the sensor and boil some water. The sensor resistance should be infinite when it is colder than the overheat temp and 0 when higher than the overheat temp. Just note that the resistance does go to 0 when you dip it into boiling water is sufficient to confirm that it is working. To test the actual temp of the engine is a lot harder but suffice it to say that if it is overheating you will notice lots of steam coming out of the overflow!!!
The alternator can be tested by just measuring the voltage between the + terminal and engine ground when the engine is on and the alternator is turning. Should be more than battery voltage. If you have an electrical panel volt meter just watch it as someone starts the motor. You should see the voltage rise by at least one full volt.

If all that checks out then I’d be looking at the power circuit to the buzzer.
Note that there are several different wirings for the various boats. This is just the one that makes sense for a ¼ loud buzzer. Your mileage may vary.
Each sensor has power to it all the time. The following is complicated so ask if it does not make sense. The GROUND of the buzzer is connected to each of the POWER wires going to the sensors. The POWER wire is connected to the power from the ignition. There is a diode on the ground side of the buzzer. So when everything is honky dory and all the sensors are “open” there are 12 volts to each side of the buzzer. If one of the sensors ground it causes the ground side of the buzzer to see 0 volts, current flows from the buzzer power and it sounds off. So poke around behind the engine panel to find the diode and make sure it is not going bad by testing the voltage across it when the buzzer sounds. There should be only a 0.2ish volt drop at full volume.

Bill Roosa · Apr 25, 2011

correction the oil pressure is open when the engine is on and closed when it is off.
so infinit resistance with the engine on and 0 with it off

Yanmars engine alarm

Ronallen

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Ed Schenck

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Steve Dion

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John T1594

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Bill Roosa

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Bill Roosa

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