Offshoreonly.com - 496 Mag Black Soot on Transom Lots of it

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You might consider installing your own air/fuel ratio gauge(s) rather than paying a mechanic to install and view them for you. Then you would know what is going on all the time.

Bob @ Dana Marine stocks risers for the 496's with the O2 sensor bungs already installed. Call him up and buy the replacement risers (~$125 + shipping, exchange). Then you need a wideband kit. Dynojet offers the WideBand 2 (http://www.dynojetwb2.com) as well as both gauges and/or a touchscreen LCD display with logging capability to record the data. Take a look on the website.

Has anyone had their ecm reflashed recently I have the same boat and the same problem....not as bad but I was wondering what the cost might be?

I had this same issue on both my HO's when I first bought my '03 Sonic a few years ago. There was a recall on the ECM, but they never got the new program. Of course, Mercury only did it for free so long and they wanted crazy money. I got the new program done by Precision Marine, pmefi.com for way less. They both run clean, now.

They are a little more than $125.. I just installed mine this week, they are $245 plus shipping from Dana.

http://www.danamarineproducts.com/Pr...8-712952dfd524

Then you need an o2 sensor (at least one) for another $90 from Jeg's or Summit or wherever.

Then you need a FAST o2 computer to reader for about $500, unless you can borrow one.... Which I did.

Good luck-

Quote:

Originally Posted by launchpad475 (Post 3423852)

do they fit stock 496 manifolds thank

Quote:

Originally Posted by low_psi (Post 3420442)

I have an 01 496 Mag (NON HO) that has just over 300 hrs on it. Since I have had it (2 seasons) it has always left my transom covered with a greesy soot. As the water temprature rises it does seem to get better but still well beyond what I see on other boats running the same motor. I ran the boat for aprox 1 hr at 3500-4000 rpm and the transom was completly black. My merc. mechanic has scanned the ecu numerous times and every thing looks good as far a fault codes. Also at idle the air/fuel ratio looked within spec. Should I pay to have the mechanic take the boat out and check air/fuel ratio during mid-range and wot operation? I have already replaced the IAC due to abnormal air/fuel ratio at idle (last season). What would cause a super rich condition in mid-range rpm? The boat seems to run great other than it is a pain in the butt to clean the transom up after short hops from the launch to our party spot (11 miles)... I have pulled the plugs and they look normal. However I have not done a high RPM run/shut down to do a plug check as of yet. Any help is greatly appreciated.

Also my mechanic has verified there are no recalls/bulletins based on my serial number (I remember reading that some of the 496s required a reflash of ecm). He has told me the 496 ecm was programmed to run the motor a bit richer, however I believe what I am experiencing is not by design.

There's about 40 calibrations later now then your 2001 version which was the first year. They are leaner now and have many updates. Some of the soot is because of the PCV location in the manifold, the rest is from slightly rich conditions and very low timing/spark advance. There not overly rich per say, most average 13:1 at idle and 12.5:1 at WOT. A little rich for a NA motor but certainly not bad enough to cause excessive soot.

Another source of soot is the octane of fuel, if your run 89 or 91 instead of 87 with stock cal, you'll get more soot. You need to run 87 with stock cals for the low timing advance.

Not sure where my head was at when I posted this but I have an 03 not an 01. But the problem is still there. And I ONLY RUN 87 Octane.

Quote:

Originally Posted by low_psi (Post 3423975)

Not sure where my head was at when I posted this but I have an 03 not an 01. But the problem is still there. And I ONLY RUN 87 Octane.

The 2010 flash is better than the 2003. 2007 and up cals were pretty good. If merc won't update you, we can.

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Originally Posted by Whipple Charged (Post 3425422)

The 2010 flash is better than the 2003. 2007 and up cals were pretty good. If merc won't update you, we can.

How Much? My Merc Mechanic is slammed and I am sure it won't be free anyway.... I would like to be able to overnight it to you, get it flashed and have it overnighted back (if that is possible). I am in Michigan and with our short season, I don't want it tied up for any longer than 3-4 days....

Merc got back with me and said they would do it free of charge. However, I am not getting a feeling of confidence when it comes to turn around time. So I spoke with Dustin over @ Whipple and am sending the PCM to them on Monday for re-cal and should have it in hand by Friday. I can't wait to actually see my transom after a run...