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496 beep and rpm fluctuation

Old 09-11-2017, 02:41 PM
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Default 496 beep and rpm fluctuation

I have a 2006 496mag that has a single beep and rpm fluctuation all within a fraction of a second, but the motor never shuts down. This was happening once every time I would start the motor. It would usually do it while warming up, and it wouldn't happen again until I shut down and restarted. but it would only do it once. Now it has become a problem and doing this whenever it feels like it. sometimes it will stop for a few minutes, then comes back again. It seems to stop if I put the boat in neutral and bring the rpms up above 1200. Only one motor has the symptom.

I scanned the motor and no codes. Put in a crank sensor just because I had a spare, no fix. Cleaned battery connections, no fix. unplugged/replugged computer connections, no fix. pulled main harness plug, and its clean.

Does anyone have any ideas ? I'm going to find the ground connection on the block and clean that next.

The battery is at least five yrs old on that side, I thought I would try replacing that. Maybe take a look at the key switch ? swap computers from side to side ??

Here is video.....


<iframe width="560" height="315" src="https://www.youtube.com/embed/ci-FFGQ5MOI?rel=0" frameborder="0" allowfullscreen></iframe>
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Old 09-11-2017, 03:38 PM
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When was the last time you replaced the IAC?
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Old 09-11-2017, 03:46 PM
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Originally Posted by Sydwayz
When was the last time you replaced the IAC?
Hmmmm....I don't think I have on this motor. I do have a spare in the boat. worth a shot.

The only reason I didn't think that would be it cause it's happening above idle.
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Old 09-11-2017, 05:19 PM
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Drive lube bottle warning horn
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Old 09-11-2017, 05:26 PM
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Ive had drive lube warnings before. They never killed power to the motot before. You and actually feel The motor shutting down briefly
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Old 09-11-2017, 05:30 PM
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If you have DTS you DO NOT have IAC or IAC muffler - Close to 35 percent of 496 do not have IAC nor the muffler in sport boats. With that said do you have Mechanical throttle & shift or DTS. That the question that needs to be answer first and foremost.

Also Cruiser and or Sport cruiser boat apps with 496 engines about 50 percent did not have IAC s because a lot those apps are DTS.

All Mercruiser DTS do not have IAC nor IAC mufflers

If you do not have DTS you will have an IAC and IAC muffler - there is such a thing as IAC complete maintenance whether you have a problem or not. IAC maintenance is part of a tune up persay.

DTS = digital throttle & shift
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Old 09-11-2017, 05:37 PM
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intermittent continuous beep OEM Merc warning horn systems is drive lube bottle

other Possible issues -- voltage problem -- and or low voltage

also

I would check ALL YOUR SPARK PLUG WIRES --- all connected very tight and then make sure one or more is not arching off something.

An engine scan should be performed without question.
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Old 09-11-2017, 05:37 PM
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No DTS here. This is happening on my formula PC.

It does have an IAC cause I've replaced the other side a couple years ago. Keep a spare now just in case. Ill try that next.
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Old 09-11-2017, 05:39 PM
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I've scanned the motor and there were no codes. Voltage read 14 on the scanner.
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Old 09-12-2017, 08:02 AM
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Have you checked the wires and connectors at the alternator?

There was a similar issue recently in the post below:

http://www.offshoreonly.com/forums/b...it-second.html

Hope you get it figured out.
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