I have a '98 Formula 312 with stock 454 MAG MPI’s 385hp and stock Merc exhaust manifolds.

Has anyone replaced the stock exhaust on these engines with EMI or Stainless Marine manifolds and risers on these engines?

Did you notice a difference in performance, RPM’s and top speed? Was it worth the extra $$$$$$?

They are lighter & they breathe better than the factory manifolds. You wont see big speed increases, but you usually can feel the added torque and you may possibly get up to another 1-3mph at best.. We sell, install & ship both systems. Feel free to give me a shout if it still interests you. Jamie / Lakeside Restorations 570-639-2628

I like the Stainless Marine

I have the Stainless on my 311 and they are probably 10 years old, still look great. I don't think you'll see a huge change in speed but the piece of mind is great.

I had stainless on my Cig and the sparkplugs were a bi**h to get out. My new boat has EMI Thunder plus w dry tailpipes, sounds and performs better, and sparkplugs are easy to reach. I like the EMI better

I used EMI thunders on my Formula . No speed gains. I now have Keith Eickert header manifolds. Made a HUGE difference over the EMI,s. Jeff Wurl

I put a set on with ss risers on a friends 96 312 fastech, 310 hp efi engines. Didn'T make a lick of difference..What did was the maxims props, he uses way less fuel with them..

jwurl, you stated Keith Eickert manifolds made a huge difference, did they increase the top end speed?

Currently my exhaust manifolds are fine (fresh water) just looking to add a couple of MPH'S. Both motors run very strong with no problems, but i know the day is coming when they will need a rebuild. When that day comes i will have them tweaked. I had Stainless Marine on my last boat (630hp blower motor), they worked fine and looked good. Spark plugs were a pain but no worse than the stock Merc's.

Just looking for a little bang for my buck.

STAINLESS MARINE !!!!!!!!!!!

better top end, more bang for the buck and never break !

I think EMI and SM have their places. My personal opinion of the EMI's were the stainless tailpipes are of lesser quality and hence possibly the lesser cost of the system.

I have no personal experience with them but a friend installed them on his small blocks and had some issues with a new tailpipe leaking. EMI replaced it and took care of him, so for that they're A-OK in my book.

I had SM's on my Scarab with TRS. They were installed before I bought the boat and were on there for 10 years and never any issue with about 550 hp. Now have them on my Apache for 2 years and never any issues with 800+ hp. The service and quality has always been great.

I think they're both decent but my personal vote would go to the SM's.