I really think the sooty transom comes from the fact that Merc has a tendency to set motors up a little on the rich side. They do this because they warranty the motors and lean / clean motors are more apt to blow up if run real hard for long periods of time. The reality here is that if trying to build in reliability / longevity .... Fat is where it's at !!!

I'll take transom cleaning to piston replacement any day.

You need to visit a dealer and see what flash is in the computer. They can be leaned out a bit once they are broken in. I actually had my ECUs replaced under warranty, which included a new flash.

Run ONLY 87 octane in your 496HO.

Do not run any silent choice/captains call/INTERNAL switchable exhaust at over 3000 RPM. Actually, I'd recommend 2000 RPM or less.

amen to that

What you really meant to say was " I agree w/ Tbone"

Agree with you on that one! I figured they set them up a bit rich to extend the longevity just wasnt 100% sure, thanks again for the anwsers all.Ill check with merc and see if it is a current reprogam.

And this is true! I have a freind that just had his thru hull installed this winter first time out this past weekend he ran them closed at a higher rpm and now there stuck closed.Not sure if he screwed up the compessor or the flaps but either way I always thought it was an idle/no wake feature.

At the risk of hijacking this thread, sounding ignorant and in the spirit of knowledge, could someone please explain to me the technical reasoning? I do not doubt your responses, just want to know the details. Have owned boats in the past with silent choice and have not had any problems. Very curious.

When the exhaust is open (cap't call off) the exhaust and water is free flowing through the transom, essentially with no back pressure. Once you close the exhaust (cap't call on) the exhaust and water gets re-routed through the prop, which is not as efficient in expelling the water. Once you get over a certain RPM the water being sent through to the prop is not able to expell the water as fast as it is being moved through the engine and therefore you sometimes get reversion.

That is really the very basic and simple explanation, I'm sure someone on the board can give a more mechanically in depth answer.

Thats what I wanted. Thank you kindly sir.

you hit the nail on the head w/ that explanation