stock exhaust change

[speeddmn]

Has anyone changed their stock exhaust to aftermarket on a merc 350 and if so how much of a performance gain if any?

[pocketchange 22]

Last summer I did a swap on my Pachanga, (EMI thunder exhaust) it was an easy swap they fit perfect, and came with all the brackets! Claimed a 10 % gain +/-. Noticed on take off motor wound quicker, gained 500 rpms.
stock exhaust has about 2'' hole to an easy 3'', plus manifolds are tuned.
You can run all day, risers, feel like bath h2o, You will see more benafits with a built motor of course, did originally for cool factor; and serious weight loss.
Stock: 120 lbs. EMI: 32 lbs. (including shipping box)
If bigger power is in future, this is where U start. Good luck on the swap!!!:devil:

[speeddmn]

thanks for the info

[Ryan00TJ]

I bought Glenwood aluminum powdercoat HP manifolds and 4" FastGlass stainless long risers back in 92. Pulled the motor, installed blockoff plate, cut transom holes installed tips, reinstalled motor. On a relatively stock Merc 260hp 350ci I gained about 2 mph and about 200rpms top end. Motor felt more responsive and sounded much better.
Like pocketchange 22 said it did save quite a bit of weight.
Just changing the exhaust is not a good buy in $ vs performance returned. If you plan on going with a stroker, cam and heads etc later on it will then be worth it.

[lradamson]

I put the EMI Thunder headers on my Essex 21 with the Mag 350. Black powder coat with stainless risers. Clean swap and gained about 500 RPM also. They have been on for 5 years with NO problems. Adds a nice sound to the small block.

[cfm]

I installed the Eddie SBC the other year. I can't say as to performance increase because I replaced an ill working Quadrajet at the same time and did a few other tuning mods including prop.
However, I weighed the stock and Eddie system during replacement/install:
Weight
OE Manifolds Weight = 64lbs each X 2 = 128lbs
Eddie Marine SBC w/ tails = 26lbs each x 2 = 52lbs
Net difference = 76lbs total
==========================
I can tell you that the boat ran 52.5mph before carb problems. Stock 5,7 Mag with a tough life (ie: WFO all the time) Added better intake, blocked intake gaskets, BG650 carb, and Eddie Marine exhaust. I did play with new carb and timing. Had to change props due to overrev (same style prop just 2" more pitch) and now boat runs close to 7mph faster in good conditions.

[71tahiti]

I have a set of EMI's for a small block that I would sell..... let me know...

[Megabite]

Id be intrested, how much are you asking? lcjdny@yahoo.com
Len