CigDaze

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!!!

29 OUTLAW

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?

CigDaze

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.

Vonbongo

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%

Sydwayz

iTrader: (1)

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

CigDaze

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 so that should explain it.

DONZIMAN2

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.

Croozin2

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.

CigDaze

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....

tahoez71

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