No...I dont think the EMI's will make more HP that Gill's...Stainless Marine...Rex Marine or any of the others. The numbers that all these guys fabricate...key word here is fabricate...is nothing more than pure BS to me. All the manufactures "claim" more HP than their competition. If they really do add 25 more HP, or 50 HP more than the other guy, then why do we all need to change cams, intakes, carbs or distributors. Point is they can all do their dyno testing and come up with the numbers that they want...real or not. Hell...I can take your Briggs & Straton lawn more motor and put it on a dyno and show that it is making 600+ HP by doing exactly what all the manufactures do...as well as some high performance marine motorbuilder shops. Its more of a feel-good thing on the exhaust manifolds...one person might like brand A, and another likes brand B. They are all roughfully the same and they will all give you about the same. It just depends on whether or not you want to pay double for brand A over brand B or vice-versa.

That pretty much confirms with what Gellner had told me then. About 25 hp gain. Depending how efficient the hull is you pick up about 1 mph per 13 to 15 hp gain.

you serious?

There you go, but I wont believe anything the manufactures tell me anymore. I was told by CMI that I would be noticing something like 100 HP when I got the headers...then I pulled my head out of my @$$ and figured out that I had been had. I really wouldnt believe 25 HP either...more like 10 HP at the most in REAL life. As for how much HP to increase your speed...I have heard some doozies...10 HP to 25 HP per mile per hour. I will agree that it depends on your boat (hull) as some are more atuned to speed than others. I do not own a Fountain, but I would bet that it takes less HP to get a Fountain to run faster than it would a Baja or a Checkmate...but with some hulls, you could put the motor out of John Force's funny car in a boat and you will still have a sled.

I had gils and changed over to CMI because I got a great buy on them as well as the little extra HP. To me 2 MPH is huge and respectable with what I have for engines. There has been moments where I would have paid a boat load of cash to have that (2mph) just for a moment. I'll be on the dyno in the next two weeks and see just what it is. If the difference between the gils is anywhere from 20 to 25 HP I will be happy. If not I'm not to concerned about it. The guy that told you a 100 HP was on crack. That was very misleading if it's true. I can see why your not all about CMI however you should never have fallen for that either. We all learn the hard way unfortunately it sometimes hurts where it counts most.

I am running EMI thunders with long risers on a 693HP 540. When my boat had the stock 502 mag 415hp engine there was NO speed difference from the stock mercruiser iron exhaust. The only difference in EMI Thunder from most other manifolds is that they have individual runners like a header. Most other manifolds have just a large open area in them. In my opinion I would spend the extra money and get Keith Eckert manifolds next time. Jeff Wurl

Fixx
 

I have no idea,,just a sarcastic comment.. sounded funny to me :)