blackhawk

Thinking about upgrading my exhaust over the winter. Totally stock 415hp 502 EFI/MPI. I know there's not much to gain on a stock motor. Looking at it more for the weight savings and possible minor(500hp max) upgrades in the future.

Leaning toward EMI's right now cause they seem to be the best bang for the buck considering I am stock and don't plan on ever being over 500hp.

Also, I definitely want to keep my silent choice.

Opinions?

Chase910

Stainless over EMI because of warranty and construction. Lightning will be best performing of the 3 and will require an ECM recalibration. You'd have to get Lightning with their silent choice as yours won't hook up. Being you're in Mich. and hense fresh water, I'd opt for the Lightning, which would run $2200-2300.

Gordo

All the names you've listed are good, but do yourself a favor and look up Revolution Marine exhaust at www.revolutionmarine.com
Comparable performance at a better price.
Dealers are listed on the website and can answer any questions you may have about Revolution Marine exhaust as well as their other products.

blackhawk

Thanks guys, I actually found the revolution marine site after posting this. Also found Dennis Moore's site with his GLM manifolds. His could be the best bang for the buck!

cobra marty

CMI uni top platnum's are very nice and about $2,000.

Chase910

Well to me the question you want to ask is "Do I have to have the ecm recalibrated after the exhaust install?" If not, then the exhaust system is not much better than stock, because the stock merc ecu doesn't have much flexibility in it. If it has to be recalibrated its because the exhaust system flows so much better than stock that the engine will be in a lean condition. Most of the systems listed are close in price, you might as well put one on that's actually going to give you some performance along with the weight loss. Now, doesn't that make sense?

RaceRPM

CMI E-Top Platinum with tailpipes and cool collar, can be found for less than $2400/set

Have twin late 2000 502Mag EFI's stock with Vortech K&N filters and CMI's, and did NOT require ECM reprogram.

No black on transom and picked up 100 RPM, 2 mph

They look and sound great too.

blackhawk

RaceRPM, this is what I am hoping for. My motor is calibrated rich(black transom) from the factory so a better set of manifolds will lean it out slightly and hopefully give me better performance.

Chase 910, actually the systems listed vary quite a bit in price. This is why I am trying to get some advice. My motor will stay stock unless something happens to it and I have to tear into it(knock on wood). And even if I do I will not get radical at all. So, I guess my dilema is will a $1200 set of manifolds will perform as well as a set of $3000 manifolds on a STOCK motor?

Talked to Dennis about his GLM manifolds and he said the only real benefit is weight savings, price and easy installation. Also talked to Todd at Revolution and he states his manifolds work very well on the 502 EFI/MPI motors.

Chase910

What RaceRPM's results tell me is that the CMI E-Tops don't flow anybetter than a cast manifold, and not as well as other headers. Lets look at what I know the only back to back dyno test of a 502 mag mpi with different exhaust systems. This was printed in Hot Boat mag several years ago. The only exhausts that made the engine lean which required an ecu reprogram where the CMI and Eickert exhaust. Why did they make the engine lean? Because they were flowing so much better than stock that the ecu couldn't compensate enough with additional fuel. If you look back the E-Top wasn't tested...I think it was either the 2 piece tube top or sport tube. None of the cast exhaust systems, Imco, eddie, Stainless flowed enough to warrant a reprogram...yet they all did increase the hp, tho not as much as the Eickert or CMI.
Now, look at what Merc uses on the 525, that is not an E-Top exhaust, it is close or is a version of the Sport Tube. It would seem to me Merc found this exhaust is what they needed to support 525 hp. This is also what CMI states on their web site, that the Tube top and Sport Tube are for 1hp per cu in engines, and your goal is around 500hp/502ci or 1hp/1ci. Look at the Lightning exhaust, designed very close to the CMI Sport tube, the primary exhaust tubes are much longer than E-Tops, flowing back towards the transom before joining the collector, this seems to be a better flowing design. Stainless Marine's best header is the Hi-Torque Gen-III. This is what is raced and if you look at its design it is like a tubular header in that the exhaust is seperated until after it turns towards the stern. If you want performance as well as weight loss then these are basically your four options, CMI, Eickert, Stainless, Lightning. Only the Stainless might work with your stock silent choice, the others you will have to buy their silent choice system. For the Eickert you will have to get Corsa to build you a silent choice system. Not sure where in Mich you are but I know there are several people in the Monroe Boat Club that are running the Lightning Exhaust, so they could give you some feedback.
Tough to beat the price of the Revolution exhaust, I just don't think that will get you to 500hp with mild upgrades, ie. no blower.

blackhawk

Chase 910, thanks for the info and I totally agree with what your saying. Except for the fact that raceRPM's manifolds didn't flow any better than stock. Like he stated his black transom went away and he picked up some rpm and mph. I would say that means they are flowing better than stock. Maybe not a lot but they seem too have leaned out his rich condition. Do they flow as well as the CMI, Eickert, Stainless, Lightning? No, but am I really going to get that much more out of my stock motor running one of them? I guess that is the big question. Spend $1200, lose 50-60 lbs, don't re-program the ecu, keep my silent choice and pick up a mph or 2. Or spend over $3000, re-program my ecu, buy their silent choice and pick up how much mph? If it was 5-6 mph I would do it in a heartbeat. But we all know that it won't happen on my stock motor. And I totally agree that higher hp motors need the better flowing design. But, like I said, I want to keep my motor stock unless something happens(knock on wood again!)

Ah hell, now I'm confusing myself!