I'm kinda confused with when you need to upgrade your exhaust system...

When you go up in HP from the stock 260-300hp to say 350-400hp... do you need to get performance exhaust? I DO NOT want to upgrade/spent 1,500.00 if I really dont have too on some stainless marine exhaust...Ive herd you really dont even see a performance change when putting on the performance exhaust on.

Your cam selection will more determine your need to change to a different manifold/riser setup than a HP number. Merc's 350HP Scorpion small blocks came with the standard cast iron manifolds/risers.

at that power level, you should be good with stock or aftermarket manifolds and good risers with a 4 inch through hull exhaust. for headers to be worth while you would need to be at a much higher power level. high dollar exhaust sure does look nice and pretty though!

LOL, yes... i know they sure do look good... so if i do hit the 400hp then ill just do the HGE aluminum stock replacement Manifolds... 229.00 each sounds good to me. Saves 100lbs.

http://bpi.ebasicpower.com/pc/HGE7114ALUM/MPMANIFOLDS

You will want to upgrade when you need new manifolds or you want to spend a bunch of money for little to no gain.

LOL spend a bunch of money for what?!?! Oh yeah... Bling Bling!!

I heard you pu 1 to 3 mph from weight loss and improved flow

You'll get gains if the boat is really weight sensitive and/or your old exhaust is falling apart.

You might get some gains from more power if you are on the higher end / cammed up.

My brother did really good with a new exhaust on his old 22 Donzi, he picked up a couple hundred RPM when he went to CMI if memory serves. That was a Big Block though and I think they respond better to the exhaust. SB with the 4 inch exhaust already flows quite well for the engine.

On my old boat I did exhaust but I also did a new carb, fuel pump, among other things. I picked up a bunch of RPM... the old exhaust was rusted out junk so I don't know exactly where it all came from.

Yeah... with the 4 inch IMCO stainless risers i have and some new aluminum HGE manifolds will be fine for the time being... like i said... Im going for 350-400 hp... thats it. I dont want to be hurting my alpha SS...

I did the same with the 383 that was in my old boat, but I also had the risers extended to the transom tips (BIG roller cam... for a marine small block away). I had less than a grand in the whole exhaust system, and it supported close to 500 HP.

I'm now using Merc/Gil (496) manifolds on my 454 Mag.