Weird alarm and engine stall

[johnfalk]

I am getting an occasional brief alarm and very brief stall in my 8.1 l Mercruiser (2007 Sundancer 280, 420 hours). This happens both at the dock and at slow speeds. Before and after, all is running well. In addition, I have had a single occasion where every gauge on the dash except the tachometer froze. Engine continued to run normal, and the gauges came back after stopping the engine. Also, one time the Smartcraft gauge showed '0' after the stall, but then returned to normal. And, also on one occasion, I was not able to set my speed between 1000 and 1500 RPMs. Next time I started up, all was normal. I have paid two mechanics to do diagnostics and both report no error codes or other problems. Grounds look good. Any ideas? I am going north into bigger water for a couple weeks soon and am concerned whether I should go or not.

[gregk]

That is a strange one, electrical gremlins are never fun. Does this happen when the engine is hot or cold? If only hot, it might be something related to an intermittent electrical component starting to fail. How often does it happen? I assume it is not easily reproducible. Could be a short in the wiring harness somewhere. While it is running, I might suggest moving/jiggling around your key, battery switch, all wiring harnesses, wires on your battery, wires to the alternator, engine connections, etc. I would also try turning on/off all items on your boat, radio, bilge bump, head, windless, etc. Try to get a volt meter on there to look for drops.

What alarm are you seeing? Low voltage?

[johnfalk]

The alarm happens when the engine is hot and cold, and only once every three or four times out in the boat. Mechanics jiggled wires, but I will do some of that myself. They also wondered if it might be the ignition switch. I will investigate that further. You are correct, not able to reproduce the problem. The alarm is probably a half of second long, so I have not been able to see any readout. All very strange. Thanks for the tips.

[gregk]

I would look closer at the ignition switch. It sounds like your power is getting cut out. When you first turn on the ignition switch you also get a beep when it initially powers on. If the power cuts out and back on again, you will get the beep again. The ignition switch on my 2003 260 Sundancer failed after about 10 years. With the battery switch off, you could try turning it on/off many times to try and clean the contacts on the switch. In my case, a generic Sierra 4 position switch SIE-MP41040 did the trick for around $30.

Best of luck, let us know how you make out.

[johnfalk · Accepted solution]

Excellent idea. Will do!

[johnfalk]

I replaced the ignition switch and so far have had no alarms or stalls. I think this might have fixed my problem.

[gregk]

Great, glad it worked out. Enjoy the rest of your season.