Transom sutt?
 

Not sure if this is a common problem due to the fact I am just now acually getting into performance boats/thru hull but every time I take my boat for a cruise I end up with a consiterable amount of residue under the swim platform and in between the blower ports on the bottom of the platform.Oil consumption is very little which leads me to believe its an excesive fuel problem.Not sure if these ecm's are reflashable but I will look into that more.Any input would be great... Sorry if this sounds like a noob question but I just wanted to try and see if this was a common ordeal.
Oh the engine is a 496 HO in a 27 .....Thanks

What octane fuel are you running? If its higher than 87, it will just soot up your transom.

I have the same problems on my 525's. It gets worse in the hot -- humid days of summer. As Beak said use the right octane. Don't go any higher than recommended. You won't get an increase in performance and the soot will be worse. Plus it is a waste of money. Right now in the cooler less humid air it is not bad. I just clean the transon after every run.

Same here. Heavy soot with 93 octane. Switched back to 87 and its decreased tremendously, not completely, but I would say at least 50%. Been running the silent choice for most of the day on the water, only switching when making a run or to be an attention "whore". Thats helped more than anything.

Yes, check out the ECM revision. I found out my '03 496HO's never got a fix for the fuel injection voltage. After the update that was installed by Precision Marine(pmefi.com), my transom soot was cut to about 1/4 of what it was before.

I heard you are not suppose to run your silent choice over 2k rpms

I could be wrong

I have no clue. Thats new to me, though a lot in this sport is new to me.:grinser010:

My 502's do this also, as did my previous 27'. Can start off with a clean transom, run 5 minutes and it's got a film already.
Sincethe motors are the same as what's in other boats that don't seem to be as bad, I chalk it up to the design of the swim platform.

I was told not to have the silent choice closed unless I was below 3,000 rpm.

that could be the magic number, I didn't think you were suppose to run WOT with it closed, or you could get reversion.

I don't recall what thread I read that on. I don't have captains choice so I didn't pay that close attention to it.

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:ernaehrung004:

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

:evilb::evilb:

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:cool:

I did have the ECM's reflashed for my 525's and the soot is much less, but still there after a hard run. Which is most of the time. Big Time's explanation is right on. Tbone, everyone knows you are the bestest and smartest. The only reason I knew to run the silent choice below 3K was because there was a sticker or warning in my owner's manual on my old boat with 496 mag ho's that said not to do it.

You have forgot more than I know:cool: