Hy-Velocity

Have just completed a exhaust swap from stock to the Eddie Marine system (EMI 511) on a 2004 Velocity 290 SC with a 496/425 Mercruiser engine. This was the first application of a Eddie Marine exhaust system on this engine so we were in uncharted waters but all went well, with great results. The boat has 31 hours on it and the exhaust exits straight out the transom. It went from 70 to 73 mph @ 5250 rpm and now it is up against the rev limiter so a prop change is in order. For the full story pick up a copy of the May issue of "FAMILY & PERFORMANCE BOATING MAG.

DiamondPerformance

iTrader: (2)

Can't beat the price also!

Hy-Velocity

Yup, you are right. Great bang for the buck.

bn

So the only modification was swapping out the exhaust?

Hy-Velocity

bn, yup thats all that was done.

KAAMA

iTrader: (1)

Hy-Vel,

Wow...that is a nice performance gain for just bolting on exhaust. I have heard that the stock Merc 496 exhaust is pretty crude. Congrats....money well spent! I am sure it must look better much better too. I am also sure it must have a much better tone/sound to it than the stock Merc exhaust too---right?

Indy

3 mph from just an exhaust Conventional wisdom says it would take 60 hp to get that extra 3 mph. I don't think the Merc engineers could be so off. I'll bet temp/humidity/water conditions had more to do with it. Sorry to be skeptical, but in case I'm off base here...congratulations, you made out well, people on the board here pay big bucks for 3 mph gains.

pullmytrigger

Thumbs up!!!!!!
have you ever been on the rev limiter before the swap in ANY conditions.....if not then Id say your gains are for real....doug

pullmytrigger

How did Fam/Perf Boating (my favourite mag) get ahold of the story???

Raylar

Glad to see some results in on 496 exhaust whatever they are. The Merc exhausts are not as crude as one would think, remove the restrictor, "turbulator plate " and you will see 10-15HP at 5250 on stock exhausts. We have some internal Merc manifold "secrets" that our kit people get. I think we have done more exhaust system testing on the 496 that anyone in the country and I am a little suspect at 3 miles per hour more under exactly same conditions. I think the test will have to be a little more scientific than this to show the exact gain. I am sure that any exhaust systems that flow better at 4000 rpm to 5400 rpm will add power to the top end of the 496 and hence should increase power and speed slightly. I also know that good longer tube 4 tube or TRI-Y systems will increase torque and horsepower over even modified stock 496 Merc manifolds. If you want a better look "bling" and some more power the polished tubular headers are the way to go, but for any of these conversions you have to look at the cost per HP and FT/lbs torque ratios if you are trying to get the most" bang for your buck". I met with the people from CMI at Miami and we had some serious discussions about developing a more cost effective 4 tube stainless header system for the 496 and we will be working with them this year to do just that. CMI undoubtably makes one of the finest tubular marine headers in thier long tube setup, but at about 5K per motor, that's not a lot of "bang for the buck" unless you are building a really highly modified motor for your "waterrod".

Ray @ Raylar