after market exhaust with sc
 

opinions wanted on the kind of after market exhaust i should run. i really, really, want to keep my mercruiser silent choice. the setup will be whippled 540's and yes i've heard all the warnings about blown applications and silent choice, but feel free to refresh my memory. :D

From my understanding, exhaust isn't so critical on a blown application. I really don't understand why though. It would seem that because you are forcing a greater charge into the cylinder, that you would need to make sure that the extra exhaust is removed. Guess the scavange is only critical on a naturally aspirated application. Anyways, many supercharged engines make good power without an expensive exhaust system. A set of cmi tube tops would nicely on your application. The need for dry tails would be determined by how much overlap your cam has. If you keep it mild and rely on the boost for power, you should be able to keep the silent choice. Just don't go wfo with it closed.

Cord! Whoever told you exhaust on a blower application is not important has NO IDEA WHAT HE IS TALKING ABOUT!!!!
To get the most from a blower motor, you must have an exhaust capable of removing the exhaust from an engine making the same amount of power na. So if you make 750hp, you need 750hp in exhaust capability. If you restrict the exhaust, you will see some power, but not nearly what the blower is capable of. You can get good headers that will accomodate the silent choice. Try CMI.

Suprisingly, I've actually have heard it from several independent sources. :cool:

Uneducated ones!!!
I'll go to the dyno or the water or cars to see who is right!!!
I'm sorry you have bad information. That is one reason I am on the board. I can only give you what I have seen on the dyno and in the water and on wheels. Be glad to send dyno sheets or a cam to try with a money-back warranty. Just need your motor specs.

Merc exhaust is good up to about 600 hp. For a blower motor it might be wise to switch though. I have Imco Powerflow on my procharged 502s pushing 650 hp.

You can keep your silent choice but under NO circumstances run them closed while on plane. The exhaust will not be able to get out fast enough and you will melt your pistons.

Ken ,thats backwards if the exhaust can't get out it gets rich and fouls the plugs with deposits ,ect ,,,and thus cools the charge not super heating ! I know your trying to help but this is not the problem ,I've done tons of boats with blowers for years and never had a problem related to the silent choice -have a good night:D :D

Bobby, I appreciate the correction if I am wrong.

When a reputable engine builder replaced a head gasket for me this spring, they had a serious problem just after they sea trialed the boat. Oil & gas spewing out the exhaust. A compression test showed a few dead cylinders. He said that when they re-installed my air powered silent choice, there must have been an air leak in the system which allowed the exhaust to close during the sea trial. He told me that the exhaust could not escape fast enough and the heat melted the pistons.

Made sense to me.

Ken, exhaust gases will not burn. When the exhaust backs up, the power just goes away, kind of mushes, if you know what I mean, because the fire practically goes out-like a plugged catalatic converter on a car. Melted pistons could be detonation or preignition. Preignition causes the center of the piston to melt and a hol appears to have been melted in the center. Preignition looks like you took a cutting torch and cut the edges of the piston. Your problem could have been many things. Without seeing the failure I can't tell what hapened and might not know even if I did see it.

Running even naturally aspirated motors through restrictive mufflers could have negative consequences on the exhaust valves. I could only imagine on a blow motor this could be even more the case.