Over the winter I had the PCM's re-flashed on my 2002 496 HO's in an attempt to get rid of the black exhaust soot that was always on my transom. From what I have found these early 496's would run very rich causing the black soot. I went to fire the motors this weekend for the first time since the re-flash. Both motors will turn over for a bout 5 seconds then backfire. I have eliminated bad fuel as as a possible problem. Any ideas? Thanks.

iF BOTH MOTORS ARE DOING THE SAME AND YOU HAVE HAD NOTHING MORE DONE APART FROM THE REFLASH I WOULD THINK PCM ?
HOW MUCH SOOT DID YOU GET ON THE TRANSOM , I GET A SMALL AMOUNT WITH MY TWIN 2001 496HO DONT KNOW IF THEY HAVE HAD THE REFLASH ,ANY WAY TO FIND OUT ?

Nothing else done to the motors. I think it is the re-flash as well. Just wanted to throw it out there to see if anyone else ever ran into this. The soot was pretty bad after a weekend. I searched around on the forum & found some info & people that had the same issue. I bet if you could have someone wh has the capabilites of flashing them take a look at your & tell you if they have been done.

Thanks,
Brian

Who reflashed them?

I should point out Brian i am no Expert still learning my way round these motors ,the first thing i bought was a Rinda scan tool so i am ready when sh!l happens .
i live in England so getting a reflash done nearbuy isnt goinging to happen ,Good luck let me know how it works out .

sounds like the ecus,,,had mine done 2 years ago and had all kind of issues,,1st the trim did not work,,2nd time the engines would not start and cranked over like the timings was too advanced..the 3rd time I ended up buying 2 new ecus and getting credit for the reflashing,,,

who did the reprogram?from what I know only one person is MERC authorized to work on the 555 ecus

I want to give the guys who did the re-flash a chance to fix it. Thanks for the info boatnt. I hope that i'm not headed down that road. Hopefully I can get them adjusted this week. I have them out of the boat & ready to be shipped. I will let you guys know what happens.

The only two parties I would personally trust with the 555 are Eric Simon & Whipple. There may be others but those two perform the largest volume of reprogram jobs on that particular box that I have ever found. You still might have a glitch or two but that's what you sign up for and it's always good to deal with someone who "does it every day".

I am curious about this as well. I am told there are several recalls that mercruser will fix still?

I had mine done on my 03 for soot. I only ran it once so far and the soot is as bad as it ever was.I still have Stabil in the fuel with last years gas,I hope with fresh fuel it will be better. An authorized Merc Dealer can scan and check to see if they need to be reflashed. I had my 02 done and it eliminated almost all of the soot.