He had to go thru the Dealer Jeff. Dealer had to lean on Merc but they did it eventually.

Read your owners manual..... 1000 Cranking Amps is the recommended battery.... Just to clarify I did not say this was the problem... I suggested he make sure he has the right battery.... and he feels he does.... wouldn't matter how many batteries you have if they are not 1000 Amp batteries the computer in the 496's sends a low voltage fault & you go into full rich gaurdian mode.... easy way to find out is hook it up to the computer and look at the error codes...

The only way you would receive a low voltage code is if the battery didn't have enough capacity to supply 12 volts during the entire cranking process. Not at all based on the capacity of the battery. The ECM doesn't care about CCA (Cold Cranking Amps). It only cares that it sees 12 volts. You would need a very weak, small capacity battery that was unable to maintain 12 volts through out the cranking process.

I will put it to you this way. I have enough battery capacity @ 12v to burn my starter out long before my batteries drop below the required 12v necessary to start the boat.

"guardian mode" would also sound an alarm @ the dash and reduce power. Running 69mph (GPS) at close to 5000rpm is running well beyond what guardian mode would allow.

Your soot problem probably went away at right around the 20 hour mark, which was probably the same time you had your battery swapped out. From my research, the 496 was programmed to run rich during the break in period (20-30 hrs).

double post..

Didn't mean to offend. I just know that both of my 496s in the Victory run just fine, and I have two Interstate 800s. I'd know if either went into Guardian mode I think. That shows you right there that I really don't know anything!

Another double post....

My boat had 200 hours on it when I changed the battery.....

Hey I wasn't offended... and I wasn't trying to be arguementative....and I wasn't trying to be a "know it all".... I went through a bunch of BS... told to reprogram this... replace that... installed a new ECU under warranty... two years of non-sense before I bought a new battery & the problem was solved... I was just trying to be helpful by sharing my expirience... I'll leave now....

Did a check on the fuel pressure and at idle it is just shy of 40 psi and at WOT it is at around 43psi. Called my Merc Mechanic and he told me that was about right. So the little bit of soot that is left on the transom, I am going to say is being caused by the side skirts of the swim platform causing a vortex efect that is pulling the exhaust back to the transom. As mentioned earlier I have plans to pull that platform and switch for a tublar platform over the off season..

GRH, I understand completely. I have done things that I thought "no way this is gonna fix it", and found out it worked perfectly. I truely think these modern, computer controlled, finicky engines have a mind of their own. You simply stated personal experience, and I thank you! Sometimes, the improbable fix works.