Excessive Transom Soot
 

Hey Guys(and Gals),

I've got a 2001 496 MAG HO, EFI of course, and It seems that of late, I have developed this little annoying soot problem on the back of the boat. It's a recent phenomenon for me, but I've read others complaining about it in the past. I had the same problem during break-in(about the first 10-15 hours) but then it went away or was very minimal. I would only notice it after many hours of boating.

Now it seems that I have to clean it off at the end of every day or it REALLY builds up.
It also seems the worst when it's cold outside(50's and 60's). Could it just be due to ****ty winter gas or do I have a problem? Is it something to worry about? Other than the soot, there's absolutely nothing wrong that would be noticible. Performance is the same as always.

Thanks for any info!!!
:)

Like you, I had soot from my HOs for the first 10 hours. Since then almost none. I'm at about 50 hours now. What are your hours up to?

Hey 29, I have 91 hours on the motor as of yesterday.

The reason I asked about the fuel is that it was at about this time last year when I started to notice vapor-lock and troublesome idling on my 350 Carbed motor in the hammer.

I heard that there is an additive in winter-grade fuels to alter vapor pressure in colder weather. :confused: :confused:

Someone mentioned that if it's rated for 87 octaine and you use higher you get more soot. My 454 was terrible, I got the ECU reprogramed and added a MSD ignition boost and it cleaned it up about 90%

There has been a number of posts about this subject on the 496s and the HP500EFI. Supposedly Merc sets the thing up to tun rich for the first 10 hours or so. Then it leans itself out. I am no expert. I have the HP500EFI, a 1999 model. My transom is a lot more sooty with anything over 87 octane, and it runs fine on the 87. Also it is REALLY black in cold weather. The motor really richens itself to compensate for the colder denser air. Do a search, and you will find some more info here and on the Gen. Disc. forum.

Brian

Thanks guys for the info. I had a feeling something like that was going on. Nothing to it, right? ;) I use 89 and it's been really cold down here lately :D so that should explain it.

Have not had a real problem since break-in. Started firing the motors for warm-up with the Q&Q on. When they are cold it seems worse. Probably a function of the cold weather. Lots of Wax on the transom helps on the clean-up.

Hey Daze,
The reason it's temp related is the fact that the ECM's are programmed to run richer the cooler the engine temp is. These EFI systems don't have a "choke" so the ECM has to change the air/fuel ratio or cold starts would be a *****. Have you monitored engine temp since this began? You may have a thermostat stuck open keeping your engine temp low. I don't know about the first 10 hours being rich but temp will definitely affect it. Old hot rodding trick when EFI first came out on cars & trucks was to run a 160 therm instead of a 195 and then bump the timing a couple degrees. Hope this helps.

Thanks Guys!
During the first 10 hours of break-in, it is normal and intended for less wear. Then it went away until about 3 weeks ago. You guys are right, it seems worse the colder it gets. Looks like nothing to worry about. All other things are equal and running fine. Same temp, same feel, power, etc....
:)

HI guy's, you dont want to run to rich or the extra fuel will wash down your cylinders increasing wear on pistons,rings and cylinders. Also cotaminates your oil reducing its life. Happend to me once in an extream case, made the machine shop happy and my bank account :(

Sorry to say, you guys do NOT know what cold is!! :) :D :eek:

Dude, I don't know what you're talking about but it was like, chit I don't remember....It must've been like in the 50's or something!! :D ;) :eek: :) :p

Tahoe, I understand what you're saying and it is true, but what is there to be done...It's all in the chip and the way it's programmed. I'm still under warranty so even if I wanted to do something about it, I couldn't.

Hi Baja Daze, why not try a ignition box,they clean up a slite rich mixture dont know if you can with waranty. 104 octane boost can also help, more of a compleat burn with that stuff. One more thing might help, a good set of spark plugs.All of the above have helped me in diffrent cases,hope you can use one of the ideas cuz that black soot is a pain in the a$$ to clean and the girls get very up set when its gets on there new little bikinis.

Thanks for the tips Tahoe!
With the ignition box, are you referring to an MSD or something similar.
The 496MAG's already have distributorless electronic ignition which from what I understand puts out quite a good spark. Also, the factory stock spark plugs are premium grade platinum plugs(the equivalent of automotive 100,000 mile plugs).

I'm a little confused about the 104 octane fuel...I thought using higher octane than required will produce MORE soot. :confused:

Thanks again! :)

BajaDaze,
Check out this thread, I've had a constant problem with this, my HP 500EFI's run so rich that my oil was 5.5% fuel diluted after only 18 hours running time. I would highly recommend doing oil analysis with every oil change, it brought this problem to my attention. Also, you may want to have the ECM's reprogrammed, I'm sending mine to Tyler Crockett.
Good Luck,
Paul http://207.55.218.179/cgidir/ubbcgi/...c&f=3&t=003172

Thanks Boathead. Good reading and it seems all too common. Perhaps the 496's are set-up in much the same way.

Mine sooted up until the 10-12 hour mark then went away. Came back again several hours later for one weekend's runnin' then went away again....

Rick

It must be the weather! ;)
...We put a few hours on the boat this weekend in all conditions...Idle, cruise, WOT, cruise...etc, etc.

But I didn't notice too much soot this weekend...It was in the 80's, though! :D :)

Seems worst when it's cold :confused:

My two cents from what I have seen with the HP500 EFI that I have in the Camaro is that the bulk of the "richness" of the Mercury programming is in the first five minutes of operation as the motor moves towards a reasonable operating temperature. As the motor build temperature (block and oil) the richness clearly decreases and the exhaust "cleans up" - amazing what you can see with dry headers.

From experience in the car and boat - the more you start and stop the more soot on the transom. Keep in mind, the Delco MEFI3 ECU that Mercury uses is an Alpha-N system that calibrates the fuel curve based upon Manifold Vacuum, Throttle Position, and Manifold Temperature. The addition of an O2 sensor could eliminate this problem but would require significant reprogramming. An MSD 6 would certainly help (and I am going to install one here very soon) as the GM HEI ignition just dows not have the jam to completely burn the fuel at cold temperatures (very rich condition).

Thanks Adivanman!
That makes perfect sense as you can definately distinguish an audible difference when the temp comes up to normal operating range. I'm not familiar with the MEFI3 ECU unit that you mentioned, but I imagine the PCM-555 unit in my motor operates in much the same way. :)

There is one more issue that I will mention that I discoved while working through the install into the Camaro...

To dummy the story down - fuel needs spark to burn. Too much fuel and not all will burn and what does burn will tend to burn "dirty". Long story short, the coil amplifies (battery) energy to very high voltage which travels through the spark plug wires to the plugs where it arcs across the plug gap and ignites the fuel. I think we can all agree on that.

What I found on the HP500 EFI is that the Mercury Racing (Mercruiser) plug wire were VERY resistive - to the tune of 4000 ohms per foot plus. Compare that to MSD completition wires at 40 ohms per foot (give or take).

More resistance means less spark energy in the combustion chamber regardless as to your opinion regarding OEM or aftermarket ignition.

Now, I DO NOT SUGGEST THAT YOU CHANGE PLUG WIRES IN YOUR BOAT. However, the car is a different story. As best as I / we can figure, the high resistance decreases the likelyhood of leakage through the wire or at the plug boot, which in turn decreases the likelyhood of blowing your boat to kingdom come when you start it without running the blower.

Perhaps this is a Mercury or CG sacrifice of performance for safety. What this does suggest, however, is that the maintenance of the ignition system (plugs, cap, rotor) is very important, as they are handicapped out of the box.

I'll let you know how the MSD's work in the car. :)

That's great info, J.
I appreciate all the insight...Handicapped is very appropriate for the situation. I just checked the plugs not too long ago and looked fine. Perhaps something more recently(winter fuel, cold rich starts, etc) fouled them.

L8R!
Looking forward to hearing about the project completion!
-Nick

I just put 496HO'S in my 38 Special and had a tremendous amount of soot during the first five hours. It went away for a while but think it might be fuel related. I also live in Tampa and question the fuel I purchased on the last run(Imperial)because the soot really increased after a run last weekend down to Fish Tales in St. Pete.