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Mercruiser 496 intermittent alarm , drop in revs, then carries on on

freobhoy

New member
hi, i have a 2006 Maxum 2700SE with 2006 Merc 496 MAG Bravo 3. I have been getting an intermittent beep, accompanied with drop in revs, which only lasts for about a second - revs pick straight back to where they were and it carries on as before.

Seems to happen shortly after start up, maybe 5 minutes or so, but has also happened at other times and at random revs (today once at 750 and once about 1800) - but never when i am at higher revs, i.e. up on the plane.

The smart craft gauges show a drop in RPM, the voltage drops to 0.0V only on the smart craft not the analog voltmeter.

I have the vessel view mobile and don't get any fault codes.

any thoughts or ideas would be appreciated,

Thanks
 
How's your battery health?

I get about 12.3 - 12.5V ? I was wondering about batteries but didn’t think that was too bad and I get the same issue regardless of which battery I’m using.

Having said that - when it happened yesterday I had just started to adjust my trim tabs so there was an additional load?

probably worth trying new batteries.

I assume that if I put it one new battery and only use that one as a starter battery and the other for house it would be ok? I’ve always thought you should replace them at the same time?
 
I'll move my comment over here since you seemed to have missed it on your original post.

Loss of power to your smartcraft gauge would show a Comm error on a vessel view screen.

Your Smartcraft gauge it self can cause this issue. First thing to do is unplug the gauge and retest. Other than that you will need a diagnostic computer to look at the Fault seconds in the engine history.
 
I'll move my comment over here since you seemed to have missed it on your original post.

Loss of power to your smartcraft gauge would show a Comm error on a vessel view screen.

Your Smartcraft gauge it self can cause this issue. First thing to do is unplug the gauge and retest. Other than that you will need a diagnostic computer to look at the Fault seconds in the engine history.


Thanks Dockside, just going to give that a shot this afternoon see how it goes.
 
12.3-12.5 with the engines running is a big problem. If they are that low when at rest, also not so good. When running you should be seeing high 13 to 14.4. At rest at least high 12
 
I'll move my comment over here since you seemed to have missed it on your original post.

Loss of power to your smartcraft gauge would show a Comm error on a vessel view screen.

Your Smartcraft gauge it self can cause this issue. First thing to do is unplug the gauge and retest. Other than that you will need a diagnostic computer to look at the Fault seconds in the engine history.


So I spent the afternoon running some trials. Figured I’d do this before splashing out on new batteries. Did 6 or 7 starts and within 2 or 3 minutes (at most) was getting the same issue every time, beep, revs drop to ~550 and then straight back up again.

I then unplugged both Smartcraft gauges and kept my Vessel View Mobile running. First up noticed that I was getting higher voltage at lower revs, always 13.8 - 14.4 or so. Stopped and started multiple times, 5 or 6 at least, and ran the boat at low revs varying between 750 and 2000 for about an hour.....no beeps!!

I’m terrified of jinxing it by thinking that it might be solved, but so far so good! Fingers crossed.

Is there any way (apart from plugging back in and seeing what happens ) of testing the gauges health? Also - when I unplugged the 2 smart gauges I lost all my gauges (except the vessel view). Is that normal?

Thanks for your help!
 
So I spent the afternoon running some trials. Figured I’d do this before splashing out on new batteries. Did 6 or 7 starts and within 2 or 3 minutes (at most) was getting the same issue every time, beep, revs drop to ~550 and then straight back up again.

I then unplugged both Smartcraft gauges and kept my Vessel View Mobile running. First up noticed that I was getting higher voltage at lower revs, always 13.8 - 14.4 or so. Stopped and started multiple times, 5 or 6 at least, and ran the boat at low revs varying between 750 and 2000 for about an hour.....no beeps!!

I’m terrified of jinxing it by thinking that it might be solved, but so far so good! Fingers crossed.

Is there any way (apart from plugging back in and seeing what happens ) of testing the gauges health? Also - when I unplugged the 2 smart gauges I lost all my gauges (except the vessel view). Is that normal?

Thanks for your help!


Yes, What you think are "analog gauges" are actually digital link gauges hooked in a daisy chain to the smartcraft gauge.

Continue to test your engines with the Smartcraft gauge disconnected if the issue does not show up, plug it back in and see if it does.

When this happens there is no repair of the units, just replace the gauges. Maybe with an actual Vessel View.

The smartcraft gauge work on Can P and can take down Can P with no codes stored.
 
Yes, What you think are "analog gauges" are actually digital link gauges hooked in a daisy chain to the smartcraft gauge.

Continue to test your engines with the Smartcraft gauge disconnected if the issue does not show up, plug it back in and see if it does.

When this happens there is no repair of the units, just replace the gauges. Maybe with an actual Vessel View.

The smartcraft gauge work on Can P and can take down Can P with no codes stored.


I took it it out again this afternoon and it went fine, I plugged the gauges back in and it continued to run with no problems. Was kinda hoping the beeps would come back when the gauges plugged back in.

I’ll leave the gauges unplugged for the next few weeks and see how it goes.

I have an NMEA capable plotter so might rig that up as well as my VesselView mobile and that will cover me.
 
12.3-12.5 with the engines running is a big problem. If they are that low when at rest, also not so good. When running you should be seeing high 13 to 14.4. At rest at least high 12

Thanks. I checked again - I get about 14 when running and around 12.5 when not running. Probably next thing on my shopping list is new starter battery
 
Yes, What you think are "analog gauges" are actually digital link gauges hooked in a daisy chain to the smartcraft gauge.

Continue to test your engines with the Smartcraft gauge disconnected if the issue does not show up, plug it back in and see if it does.

When this happens there is no repair of the units, just replace the gauges. Maybe with an actual Vessel View.

The smartcraft gauge work on Can P and can take down Can P with no codes stored.

Took the boat out again today with the Smartcraft gauges disconnected and was ok for about 30 minutes but then the dreaded beep came back. Just once. Revs dropped and then it carried on fine.

i did notice that my Smartcraft cables only have the yellow termination resistor at the junction box at the dash - there isn’t one at the engine, although there is a label on the cable that says there should be. I was wondering if that could be causing any problems?

I’ll try and get that sorted and then try replacing the starter battery before trying to get a diagnostic scanner hooked up.
 
Took the boat out again today with the Smartcraft gauges disconnected and was ok for about 30 minutes but then the dreaded beep came back. Just once. Revs dropped and then it carried on fine.

i did notice that my Smartcraft cables only have the yellow termination resistor at the junction box at the dash - there isn’t one at the engine, although there is a label on the cable that says there should be. I was wondering if that could be causing any problems?

I’ll try and get that sorted and then try replacing the starter battery before trying to get a diagnostic scanner hooked up.

The label on the cable is probably telling you that the resistor is built into the cable.

You can disconnect the cable at the engine and retest.

Important question: What do you have on your key ring? Just a key and a floaty or a bunch of crap like a bottle opener and the gas cap key?


Off topic.... Why is it Label and Cable, not Label and Cabel or Lable and Cable?
 
The label on the cable is probably telling you that the resistor is built into the cable.

You can disconnect the cable at the engine and retest.

Important question: What do you have on your key ring? Just a key and a floaty or a bunch of crap like a bottle opener and the gas cap key?


Off topic.... Why is it Label and Cable, not Label and Cabel or Lable and Cable?

ha, no idea who made label different from cable, or table....

I think the label does say ‘termination resistor on this end’ which I assumed meant that it needs to be on this end but probably means it’s built in.

Key rings only has boat key and soft float. I did wonder if it could be an ignition switch issue, i don’t think it’s a Mercruiser switch ? Or if it could be a problem in the engine / ignition harness. Not as easy to test I guess.
 
ha, no idea who made label different from cable, or table....

I think the label does say ‘termination resistor on this end’ which I assumed meant that it needs to be on this end but probably means it’s built in.

Key rings only has boat key and soft float. I did wonder if it could be an ignition switch issue, i don’t think it’s a Mercruiser switch ? Or if it could be a problem in the engine / ignition harness. Not as easy to test I guess.

You are losing power and it can also be the key switch. Drive the boat and wiggle the key in the switch and see if you can make it happen.
These are the types of repairs I would take all day long.
 
Still having these same issues. Am thinking of changing my MPR - just swapping with fuel pump relay. Are these easy to remove / replace?
 
yes, probably right. Do they just ‘unclip’ and slide out?
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I've seen boat cables (intermittent problem) with diodes and resistors that have come loose. Each one was butt connected to the wire termination and then at the plug pin. Resistors and diodes were not designed to be connected in this manner. They are meant to be soldered onto a board or chassis stud. They don't take vibration very well when connected as cable mfgs. are doing.

I never once saw them connected in this manner when I was in the US Army working on HAWK SAM missile radars on Okinawa, Japan. There are only a few MMs of stiff wire inserted into each end of a resistor or diode which makes them subject to early failure from vibration when connected to a wire end. Check the resistor carefully for tightness at the wire/butt connector end where the wire is inserted into the resistor. if loose on either end replace it. I like to add a glob of 5 min. set epoxy to each end of the resistor or diode to add stiffness. Good luck.

If interested about Hawk Introduction to the Hawk Missile System (warning do not point at alien spacecraft) - YouTube
 
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hi, i have a 2006 Maxum 2700SE with 2006 Merc 496 MAG Bravo 3. I have been getting an intermittent beep, accompanied with drop in revs, which only lasts for about a second - revs pick straight back to where they were and it carries on as before.

Seems to happen shortly after start up, maybe 5 minutes or so, but has also happened at other times and at random revs (today once at 750 and once about 1800) - but never when i am at higher revs, i.e. up on the plane.

The smart craft gauges show a drop in RPM, the voltage drops to 0.0V only on the smart craft not the analog voltmeter.

I have the vessel view mobile and don't get any fault codes.

any thoughts or ideas would be appreciated,

Thanks

Hey guys,
I had a customer with the same issue...turn key on, and wiggle main harness at the plug and about a foot before. The clamp holding the plugs together was loose.
 
LOOSE Cable from battery AT STARTER!!! it is a pain to tighten, but voltage to computer comes off this connection and will drive computer crazy with false codes. Turn off battery power before tring to tighten. Starter engagement will be worse as this problem continues. I know its an old post.
 
LOOSE Cable from battery AT STARTER!!! it is a pain to tighten, but voltage to computer comes off this connection and will drive computer crazy with false codes. Turn off battery power before tring to tighten. Starter engagement will be worse as this problem continues. I know its an old post.

Yep...always start with the simple stuff. I've started backwards many times, and found out in the end that it was a fuse!:confused:
 
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