is it worse with 93?

Had the same with my 496 on the baja.merc rep said not to use 93 and when i put 87 in it i had less soot on the back.see if your local merc rep can reflash the computer and it will reduce the soot problem a little.at idle i would put on capt.choice so it would go out the prop instead of on the back of the transom.

I've checked locally about having my PCM reprogrammed, everyone tells me Dustin at whipple is the only one that can do it yet. Just curious if it helps or is it a waste of time and money!!!

When I first got the boat I was using only 92 Octane and had no noticeable soot. I have since switched to 87 Octane at the recommendation of several forum members. I now have more soot. But I don't think this has anything to do with the octane switch. Everytime I take the boat out I hardly do any idling. It wasn't until last week when I had to do long periods of idling that the soot buildup became VERY noticeable. So I think it's more a function of low speed idling and the PIG RICH A/F ratio's on the stock PCM.

We don't have 93 octane in AZ only 91

probably the same.
gas is getting worse every year.

what happened to BHOCKETT? Like to know what the outcome was

Paging BHOCKETT, whats the update how did she run???

Well I pulled mine off tonight. I am going to get them polished and then I'll let you know if there is any change. I will say I will be shocked if there is a difference. What is the story on the two and a half inch horn on the end of the riser? I have never held a riser from any engine in my hand before so that may be a dumb question but I just thought it too looked like a bottleneck. My thought would be none of these things would make a hell of a lot of difference unless you start trying to make some more horsepower.

Be careful everyone that says that they'll post there finding have never returned???? Keep us up to date.