ignition alarm

smokey73 · May 27, 2016

When you say a "trip on the ignition circuit" do you mean the engine shuts down or the alarm just sounds? On my boat the alarm is also associated with low oil pressure. Is it possible the oil heats up after a long run such that when you come back to idle the oil pressure is too low and causes the alarm? Do you have an oil pressure gauge at the helm that you can watch when you bring the engine to idle? I'd be more apt to believe it is a low oil pressure alarm either due to a bad sensor, increased resistance in the wire or at the connections or a bad pump?

whatfiero · May 27, 2016

It is alarming because something wrong oil pressure dropping at idle is usual suspect with issue you describe change oil and filter or test pressure switch . Temp usuall go off when running high speed but water flow loss at low rpm's could cause as well

Ken Cross · May 27, 2016

Most (I would expect most all) are hooked to the alternator too. A loose belt or bad diodes in the alternator can also make the charge circuit fail at low RPM. I would not assume an alarm itself is the problem unless I found the fault already. Troubleshooting this should be fairly simple. First study the gauges when the fault occurs. Also look for a fault light.

Ken

smokey73 · May 27, 2016

gettinthere said:
Not alt. Which Guages?

Watch your oil pressure gauge and your temperature gauge when you bring it to idle. It might be best to bring it down slowly to idle while watching the gauges. It is normal for oil pressure to drop some when you come to idle, compared to the pressure you have at normal cruising speed (2400 to 2800 rpm or so). See what it reads when the trip occurs. The temperature shouldn't go up when you slow down unless there is something wrong with either your raw water pump or with your fresh water pump that circulates the coolant through the engine. I'd bet on the oil pressure being too low or the trip point for the low oil pressure shutdown has drifted somehow and is at a higher pressure than it needs to be. For God
sake, do not jumper out that shutdown. It is there to protect your engine from catastrophic damage. Follow what Adm Rickover taught all us nukes - believe your indications!

Ken Cross · May 27, 2016

Oil pressure, temp gage, and ammeter or voltmeter if you have them. I didn't suspect an overheat because you indicated it only happens at idle.

If no ammeter or voltmeter you can use a cheap multimeter and just monitor the voltage. Harbor Freight has them dirt cheap. Do it like this. Shut down the warm engine. Connect the meter to the battery and restart leaving it at an idle. The voltage should increase from what it was with the engine off. If the voltage doesn't increase, you aren't charging.

On the first trip out on our boat we had an overheat causing the horn, but the temp guage was reading just below 160. the problem was the temp gauge wasn't working and the boat was overheating due to a sheared raw water impeller. And it all worked fine during sea trials. Go figure.

If you really needed to take the alarm out of the circuit, just disconnect it. It shouldn't effect engine functions. I just don't expect the warning is the problem, but rather it's doing what it is intended for.
Ken

Stu Jackson · May 27, 2016

What engine do you have?

What gauges do you have?

Ken Cross · May 27, 2016

What breaker tripped? It sounds like it may or may not be related. I'd be careful resetting any breaker until you know exactly why it tripped. Boat fires are just plain scary. In the aviation world you never reset any breaker more than once. Never reset any big breaker without knowing exactly why it tripped.

Ken

Bill Roosa · May 27, 2016

The alarm works of a differential voltage concept. 12 volts is applied to both side of the buzzer under normal operating conditions. when a warning switch (not the gauge sensors the switches) turn on it ground that side of the circuit and current flow through the buzzer. If the buzzer is not sounding loudly that would indicate that the switch side of the circuit is (incorrectly) not grounding well. Probably a wire from buzzer to switch on the engine has a bare spot and just touching.
Good luck

Ken Cross · May 27, 2016

Okay. That should usually provide power to the start relay which drives the starter solenoid, the warnings, guages, and possibly the alternator field.

What kind of engine do you have? (I have some Yanmar schematics which could be a big help.)
Ken

Bill Roosa · May 27, 2016

The electric fuel pump is part of the instrument panel circuit....sooooo when the breaker pops due to the short in the buzzer to engine idiot switch it also de-powers the fuel pump and the engine stops.
A good circuit diagram would be helpful at this point.

Ken Cross · May 27, 2016

Sorry I got nothing on Perkins. Maybe online search.
Ken

bawlmer · May 27, 2016

First let's try replacing the breaker. Sounds like the logical problem to me.

Maine Sail · May 27, 2016

Your lovely wife is a smart one!!!!