When I purchased my boat a 2 into 1 tailpipe was installed. That was how it was raced with supercat motors. I now have quad rotor whipples. Would it breath better with 4 tailpipes rather than 2. I really like the sound of the current set up but performance is why we do this. Any motor guys have any imput?[ATTACH=CONFIG]537079[/ATTACH]

Exhaust is not as crucial on blower engines compared to NA engines. The boost will force the air through and compensate for less than optimal exhaust.
What you may see with the current set up is slightly higher boost pressures than a traditional tail on each side.

With the HP you have now, I'd bet you would see some HP gains with 2 full length tails per engines. How much gain and is it worth it are the real question.

Not so sure if you gain any speed ,by dis - connecting the left and right cilinder banks with the Y pipe ,the suction effect is better ,thus the cilinder banks help by using the gaspulses to suck exhaust gasses out ,so the intake charge become easier to go in the cilinder ,Griff is right about the blower engine is forcing the mixture in ... one would say the exhaust therefore is not so important on a forced induction engine ,but I saw on my friends dyno a big big )difference in using a Stellings exhaust VS a Keith eickert ( on a 522 ci BBC with blower /intercooler ),the motor was set up on mixture with the KE ,s ,and lost almost 200ft/lbs torque when switched to the Stellings (which have very unequal runner lenghts) the motor was running very rich with the Stellings ,so they were thinking there was something wrong here ... after some checking ,they set the KE,s
back ,and also the almost 200 ft/lbs came back....
All those marine exhaust systems don,t have a real merge collector ,most run 4 inch collectors ,or 4,5 or even bigger ,the keith eickerts ,have 3,5 inch merge collector ... when going bigger after the merge the gasses expanding and suck harder on the exhaust system .

200 ft/lbs is huge. I am unclear on the KE setup. I had Stellings on my last boat so I am familiar with those. The Y pipes are very distinct in sound. Thanks for the imput.

You mean the cast alum thunder & lightning,s ? GT perf say,s kind of the same thing not allot of diff in tube or aluminum header,s on forced ind .

I'm betting they did the Y for better power coming out of a turn...

I think you have a really nice set up there and I would never change it. If you change to twin pipes, it will be louder and you will loose the smoother sound that I'm betting is the reason you say you like the way it sounds.

What's the I.D. on the single outlet? It looks like it could be a little restrictive in the photos.

Yeah i mean THE cast aluminium KE,s , They have long runners and a Nice merge collector , THE Stellings however have very very unequal length runners , no merge collector. THE 200 ft/lbs loss when switch to Stellings could BE less if we had changed THE mixture leaner, but why would one do that !! THE prove was already there ! THE mixture went very rich when switching to Stellings , that would tell everything

The I.D of the tailpipe is 5 inch