Over-rev Warning Horn on 496?

[Carl C]

Today I took my 22C ('05, 496 HO) out deliberately underpropped for some testing. I gradually let the rpms go up and at exactly 5,000 indicated on my tach I got an intermittent warning horn. I backed off; gps indicated 65.1 mph. I tested again and this time got a continuous horn at exactly 5,000 rpm. My Mercury manual makes no mention of an over-rev warning horn. According to the manual an intermittent horn means stern drive oil is low and a steady horn indicates low oil pressure or high engine temp. The manual also states "Engine Guardian Strategy will also reduce engine power to 90% of maximum if any sensor on the power package fails". My question now is: is there an over-rev warning horn and should it sound at 5,000 rpm. You guys who have hit the limiter, what were the signs? Thanks.:confused::boggled::(:bonk:

[BUIZILLA]

5050 is the trip point

[Carl C]

5050 is the trip point I'd heard 5,150 but more important - is there a warning horn? Or do you mean 5050 is the trip point of the horn?

[gold-n-rod]

As predicted, your tach is OFF!!!!!!!!!!!!!!!!! :eek!::bonk::bonk::bonk::confused:

[Carl C]

As predicted, your tach is OFF!!!!!!!!!!!!!!!!! :eek!::bonk::bonk::bonk::confused:Wait a minute now. If 5050 is the "trip point" like Buizilla said then the tach is within 50rpm.

[BUIZILLA]

tach is not your problem

[undertaker]

Carl, you are on the rev limiter...you will get a continous horn when you are on the limiter if you stay on it a little bit longer it will then go into guardian mode and the motor will start to miss, etc.....had the same problem with my stock prop after exhaust change my tach read about 5100....The rev limiter is 5150. After I changed my prop, I still had the horn going off but at a lower RPM, thus we found I had a water flow issue.....


Undertaker:pimp:

[Bryan Tuvell 33ZX]

Horn? I get a BEEP BEEP at 5100 on both motors. They don't cut out at all, of course I pull back a hair, it is pretty rare for me to hit the limiter unless I am trying to.
Interesting.

Bryan

[Carl C]

Carl, you are on the rev limiter...you will get a continous horn when you are on the limiter if you stay on it a little bit longer it will then go into guardian mode and the motor will start to miss, etc.....had the same problem with my stock prop after exhaust change my tach read about 5100....The rev limiter is 5150. After I changed my prop, I still had the horn going off but at a lower RPM, thus we found I had a water flow issue.....
Undertaker:pimp: OK thanks. I may take it in to be hooked up to diagnostics. Will also replace fuel filter which is original. If everything checks out then I need to try props.

[RedDog]

I thought 5150 was the rev limit on a 502 but the 496 was something less?

[Carl C]

Horn? I get a BEEP BEEP at 5100 on both motors. They don't cut out at all, of course I pull back a hair, it is pretty rare for me to hit the limiter unless I am trying to.
Interesting.
Bryan I used the word "horn" because that's what the Mercury manual calls it. Apparently it starts with an intermittent beep, then a continuous beep and then the motor starts to cut out. I backed off after the beeps started. I think the motor cuts out at 5150.

[LKSD]

You may have a water flow issue at high rpms after running a while. It would be best to scan the unit when the alarm goes off while reading all of the parameters. Usually with a water flow issue one sides temp is off by more than 20*.. It also could be a damaged temp sensor.

One other semi common thing is a water over pressure fault that may happen after making mods. Although this is not that common.

The tach may be off a little bit, but it has been my experienc that they are not usually off by much at all, & If they are off you would also usually notice it at higher rpm..

That being said propping is also important & should not be ignored either.


Jamie / Lakeside


.

[Carl C]

You may have a water flow issue at high rpms after running a while. It would be best to scan the unit when the alarm goes off while reading all of the parameters. Usually with a water flow issue one sides temp is off by more than 20*.. It also could be a damaged temp sensor.
One other semi common thing is a water over pressure fault that may happen after making mods. Although this is not that common.
The tach may be off a little bit, but it has been my experienc that they are not usually off by much at all, & If they are off you would also usually notice it at higher rpm..
That being said propping is also important & should not be ignored either.
Jamie / Lakeside
. I deliberately hit the limiter so I could see what happens. I didn't expect the alarm; just thought the motor would start to cut out at 5150. If I take it in to be hooked up to diagnostics the fault codes should be in there. I think it will just show over-revving. It will also tell me if the EFI is functioning OK. I will make sure everything is OK before purchasing a new prop. Temp always stays at about 175, oil pressure is good and the headers do not get very hot.

[undertaker]

Carl, personally I do not think you have a water flow issue if you did IMO you would have the alarm at lower RPM'S (4600-4800) also like I did....most likely you were in the limiter....I would change plugs, fuel filter do a complete tune up and see if ya pick up some more revs...Jaime did that to my motor this spring I had 80 hrs. on at the time....keep us posted:):)


I think my 496 HO manuel says 5150 rev limiter, although I have not read it lately and my mind is not real good since I sniff embalming fluid fumes all day long....:bonk::bonk::bonk::wink::)