496 HO PCM Re-Flash
 

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.

Mine were redone by merc....I find the soot VERY fuel dependent. If I run ethanol free, virtually nothing.

That's very interesting Pwraddr. I have a 2001 (very early) 496 mag that sooted quite a bit. I sent the PCM back to Merc for an update (reflash) which they did. It totally eliminated the soot but also cost me 4 mph. Since I rarely go wide open it was a satisfactory tradeoff for me but I do miss those 4 mph! I never tried ethanol free fuel as it is not readily availble here. That is an interesting thought to consider though as the early PCM's would probably not have been calibrated for E10.

Dan

My 03 496 Mag does the same but it seems to vary with the brand of fuel i burned BP most of lasy summer because it was the nearest station and then switched to Marathon and found better results. I still have soot but not as much, i did try ethanol free but the station is another 15 minutes donw the road and i didnt notice that much difference.

I had a post a while back in regards to the Re-Flash of my 496 Mag (non-HO) PCM. I had my Authorized Merc. mechanic look my serial number up in the Merc. database and it did not sow any pending recalls. However, I personally called Mercury and gave them the serial number and they told my that my PCM would qualify for a free reflash to the current revision. However, Mercury would not deal directly with me. So what I then had to do was go back to my mechanic and have him send my PCM in to Mercury. The problem here was timing.... I did not want to lose a weekend on the water (Michigan boating season is short) and I couldn't get a guarantee from Mercury as to when it would be done. So I opted to overnight my PCM to Whipple and for a fee I had them put a Stage II flash on my PCM. Whipple was very fast and overnighted it back to me. Whipple also has a flash that was designed to just eliminate the excessive soot, but I figured if I was already paying for a flash (that was essentially free from Merc. why not have them put the stage II on it...). The soot did decrease a bit, however I did still have soot (but it was very greasy). But here is where it takes a turn away from the PCM. Apparently GM used too short of a bolt and bad intake gaskets that would allow oil to be pulled into the intake runners when under load n early 496 blocks.. So after a leak down and compression test, it was determined I had the bad intake gaskets.... So I ordered the updated gasket set and bolts from GM and replaced the intake gasket. Now after the intake gasket the soot I have is now very easily wipped off. However I still have the presence of a good amount of soot. I haven't really found on brand of fuel that works better than others. BUT, I believe I have a leaking injector. Upon start up I can see droplets of raw fuel in the water behind my boat, and occasioanlly can even smell the presence of raw fuel behind my boat (while at rest for a wile). Also within a few minutes all fuel line pressure is gone, after shutting engne off. Also when planing off at mid-throttle I get a small mis fire or sputter, however at 3/4 - full throttle it clear up. So my next stop is fuel injector service.

But I guess after my long winded post, my service and result from Whipple was great...

So merc can and will do this even on a older boat? I have a 2002 with 170 ish hours on a pair of 496 mags Would love to get them reef lashed with the less sooty tune.

low_psi,
Any chance you still have the part numbers for the updated gasket set & bolts in case I need to go this route also? Thanks.

Had my 2001 done before last seasons by merc through a merc dealer and didn't cost me a thing. Mine was done to clear up some possible false voltage reading by the pcm but the bonus was it nearly eliminated all my soot problems too. All my cylinder now run pretty much even by looking at the plugs. Never had an issue with the flash.

Let me see if I can find the old thread. I know I posted the part numbers in there. Raylar was helping me in that thread, I believe.

I believe the part numbers are somewhere in this thread... http://www.offshoreonly.com/forums/g...-anyway-3.html

Buddy of mine had his done from Dustin at Whipple, virtually no soot anylonger. Good investment, also better on fuel......at least he thinks...lol

I forgot about this thread. It was a great read then and was a good re-read. I think this is the gasket # you quoted 89017539.

Well I got the PCM's back from the second flash. Put them back in & the motors fired right up. Dustin @ Whipple was all over it. Even took the time to get back to me last Sunday. There are two versions of these PCM's & each has it's own "flash". I'm very impressed with the customer service that I received from the guys at Whipple. They fixed the problem right away & overnighted them back to me. Hopefully the weather holds up & I can run the boat down the lake this weekend.
Thanks everyone for all the info. Gaskets may be next but I want to run it a few time to see what happens.

Thanks again,
Brian