496 Mag Black Soot on Transom Lots of it
 

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.

i have a 496mag HO in my 24' checkmate 240zt and same deal almost always has black soot. Pretty sure thats just how they run.

I would venture to say it's normal. My '01 HO did the same thing from day one until I had it reflashed just this winter, now transom is clean as can be. The only thing I found (besides the reflash) that helped was to run premium fuel even though the experts on this site say not to it worked for me. It won't completely stop it it just cuts down on it some. You are right though the early 496 ECM's do run very rich at mid range. Good luck.

Do you run premium fuel? I had a efi 454mag and I ran 91-93 octane in with the same problem. Switched to 87 and the problem completely went away.....just a thought. Same thing on a buddies boat.

Some soot is normal. Completely black after one hour is not. I suppose it could be the design of your transom and exhaust flappers blowing everything back. As mentioned, burn 87 octane. BTW, a quick fresh coat of wax on the transom after each washing makes the soot a breeze to clean off with soapy water.

Don't run premium, only 87. It will help

Probably PCM and octane.
 

I purchased my boat new in 2004 (with twin 496 mag's), and briefly experienced the exact same horrible sooting issue during that first season in 2004.

After speaking to Merc, I realized they were well aware of the excessive sooting problem. Merc kindly sent me two new PCM's in exchange for mine. And they told me to run 87 octane.

No sooting since then!

I do run 87 octane. I have already found that the premiun burns slower so it was causing even more. Sounds like a reflash or new ecm is in order. But how do I attain either of these. How much does a re-flash cost? Also I saw Dynojet sells a fuel curve reprogrammer for the 496 mag. It sells for $599, would this do the trick? Would a reflash cost less? My boat is solid white, and it looks like my boat is a POS when I pull up with a black transom...

It is interesting that such similar engines have such opposite results, refering to 87 or 93 octane fuel. I switched from 87 after two seasons of use and ran it for another four on 93. After joining OSO I saw all the talk about how to never run 93 in a 496 so I switched back and the heavy soot came right back. Just my experience.

As far as the cost to reflash, mine was fee except for shipping because I was getting some weird codes that Merc. couldn't figure out so they reflashed it with the upgrades. Now I do run 87 with no problem. They seem to be pretty willing to reflash the older ones for a minimum amount. I would have your mechanic give them a call.

Here is a pic I took of the transom after a 15 minute run at 3500-400 RPM with a minute or two of WOT running. IMO this is way too much soot. Make my Velocity look like a turd!!

http://www.bradzgarage.com/velocity/...0606_00014.jpg

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-

do they fit stock 496 manifolds thank

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.

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...

That swim platform isn't helping either. Anyway to extend your tips out to the edge of it?

Not without it looking stupid. THe tips would need to be over 2' long....:lolhit:

Reflash should take care of it.

At idle you can see the gas floating on the water behind the boat. Just WAY to rich.

Actually, the $125 I mentioned is for them to install a bung in a stock (core) riser. Then its a swap deal for your stock riser. I doubt it's on the website - just call Bob.

PCM is on it's way to Dustin over at Whipple.

What's the cost to reflash a 496HO pcm to current code levels?

was told $596.99

contact Dustin @ whipple. I think what I am being charged is very fair. Mercury was going to flash mine for free. But I just didnt get a warm fuzzy feeling that I would have it back by Friday.

Free from Merc or $569 from Whipple?

What's the secret sauce Dustin is putting in his code??

I hope the delta in price isn't for a quick turn around!

I never said I paid $569.... I have choosen not to post the price I paid as I am unsure if Dustin wants it posted..... It may be a set price or on an individuale case basis. Contact him for pricing. And yes I am paying a premium because Whipple can get it done in a day and shipped back to me by Friday. Merc could not guarantee a quick turn around. Dustin did mention there were a few subitle differences between thier calibration and the one from Merc. But the main reason I went with Whipple is I am in Michigan and we had a terrible spring. Every weekend is valuable with the short summer season we have. So if it costs a bit extra to insure I will have a boat for the weekend. To me $$ well spent.

Just got a call from Whipple. PCM already done and being sent back to me today. Will have it by Thursday. Excellent Service!!

So how has the reflash worked out for you? Is there notable difference on the transom...I have the '03s and it's a daily battle to keep it clean.

any info on how the ecm is working out for you?

Merc just exchanged PCM's with a friend of mines 496 Mag.
No cost and the soot went away. Your Dealer should be able to push Merc on it if it has not been updated previously.

With the price of fuel these days why waste the extra money on 91 or93 octane. I read an article on here from a gentleman in texas that does installs for whipple, he did extensive testing with dyno sheets provided that prove a stock 496 will only make 1 or2 more hp with the higher octane. My 09 496s sooted up a little but after about 20-30 hrs they cleaned up & havent had a problem since

Post Results
 

Ok Low PSI.. It has been over 2 months. It is not in anyone's interest if you come here looking for advice and then don't follow up with results. Info sharing is a 2 way street here. I think we should give you 1 week to post a follow up or have everyone bombard your inbox weekly .

Chris

Relax Bud. It is summer and I am out enjoying my boat....... And if you choose to Bombard my inbox, it only accepts a few messages, then it is full so it really wouldn't hurt all that much......

Anyway on to the results. I ended up going with the stage II Flash instead of the "Stock" flash. The Stage 2 flash uses a 120 t-stat and 92 octane. That combined with the fact that my boat was running too rich to begin with has made a HUGE difference in perfromance. Before the Flash I could hit 65 on the GPS with a Full Tank of Fuel and myself in the boat. After the Flash I have sucessfully tagged 69 on the GPS (with a full tank of fuel). Mid-range pull is HUGE compared to before and planing time is reduced by a couple of seconds as well. I do still have a bit of soot, because I have to run a higher octane to prevent detonation. However the soot is a very fine soot, where it was very greesy and thick before the re-cal. The soot is much easier to clean now. Before it took a good degreeser to remove it, now simply soap and water will do the trick. I think what I see now is a result of the Swim Platform causing some sort of weird vortex that is pulling the spent exhaust back up against the transom. I have plans to switch to a tublar platform next season so I will stick it out for the last 4 weeks of the Michigan boating season..

Thumbs Up
 

Ok Thumbs up to Low PSI for the info.. Not only did you tell us about the soot clearing up but that is an impressive performance gain. This is way info sharing is suppose to work...

Chris..

It is certainly a waste to run 91+ with a stock cal, but with a modified cal, its the way to get more HP/TRQ.

More timing, different injector timing, different coil dwell, modified idle settings, higher rpm limit, relaxed codes such as water psi and standard ones such as fuel level, pitot tube psi, trim level.... We maximize for 91 or better octane, Mercury worked with 87 octane and after a few years, finally got the fuel curve semi-ok but left power on table because they target low octane.

I am by no means claiming that everyone will see the gains I did with a Stage II ECM Flash. There are a few factors involved that I would like point out. First off, my boat was running the Original 2003 ECM Flash and was running very rich, so the motor was most likly not performing at it's best. (I was only able to get around 4600 RPM at WOT). So the Stage II flash solved the way over rich issue created by Mercury. Now add to it, the Stage 2 with its changes brougth the performance up to and beyond. Add to that the "pad" running surface of the Velocity. I also removed the "turbulators" from the stock risers.

So all factors combined to a 4-5 MPH difference. I am sure if I pulled the 2 group 31 batteries out of the engine compartment (I currently have 1 group 27 and 2 group 31), pull the 40lb subwoofer enclosure out from behind the port-a-potty, pull the 80lb amp rack out of the cabin, and run a much lighter fuel load there is probably a few more MPH left in it.

There is a noticable difference in the idle with the stage II flash. Check out these Youtube videos of before and after....

This is last season before the ECM Flash:
[YOUTUBE]http://www.youtube.com/watch?v=4Jph8HmoIn4[/YOUTUBE]


And After Stage II ECM (and removal of "turbulators from exhaust risers, no other changes):
[YOUTUBE]http://www.youtube.com/watch?v=VZWLZkTa_m0&feature=related[/YOUTUBE]

Yes there have been considerable changes to the appearance to the boat, but I assure you it is the same boat in both videos. The interior has been replaced, name on transom changed (different font and colors) and speakers were added to the transom. and yes that is my fat a$$ starting the boat...