I installed (2)sets of Stainless Marine on my stock 502 MPI's last year. Pretty clean install with no mods required to accessories/brackets. There are cheaper products on the market, but IMHO, I thought they were the best bang for the buck.

I have 502s also, did you look at the EMIs? If so why did you go stainless over the EMIs...Thanks.

RE: "if you drain your exhaust after you run, you will greatly increase the life of your exhaust system."

How do you drain the exhaust?

I have ran CMI and Stellings. Both are decent exhaust. Hardly a "tuned" exhaust in most of their apps. Failures I experienced were in the middle of the collector with Stellings and at the flanges with CMI. I do not think the failures were corrosion related but "work/temperature" hardening with a fatigue failure eventually? Went to KE pipes and life has been excellent and I have probably as close as you can get to a "tuned" pipe. However, they definetly do not look as nice Then again, a dismantled engine doesn't look good either

you could pull the hose off the manifold, but I just flush them its 13yrs for me .and S/M said they tested there exhaust against others and made more power, there add was back in the 1990's they picked up 300rpm and one pitch 6.5mph with a 502 I think it said it was in hotboat or pb.

Open this valve after flushing and your exhaust will drain. If you don't have one put one in.

I am surprised at the reported SS tube style double wall exhaust header failures. I have been using these exhaust systems for over 12 yrs (fresh water only) with zero cracks or leak issues. My ***** is an mostly about an arrogant industry that provides poor service and an ongoing inability to custom fit the thru the transom tailpipes.
What is different in 2004-2006? Alloys? Import materials? Over heating?...or is it mostly salt water and lack of draining? Salt water seems like a lame excuse as it has been around a long time.
The power is on the OSO, who REALLY knows? Is it just me or is the whinning getting louder?

The title of this thread is really subjective, not objevtive enoughand really creates more negative issues than positive information here!

There are lots of good and possibly better exhaust headers/manifolds available for marine high performance engine. I can say with pretty good certainty that there are no perfect marine high performance header/manifold systems.

All of the manufacturers in this industry who make exhaust manifold/header upgrades are really making and marketing some good products. Each has its supporters and obviously detractors and each have products that differ in design, methodology and materials. Lets face it, all work better than most stock exhausts and offer some sort of measurable performance gain and certainly some added "BLING". Is one really better than another is a little to broad of a comparison.
If you are looking for all out performance it is tested and confirmed that equal length longer tube headers or manifold headers ( I've coined a new description here!) manifolds with individual runners leading all the way thru the riser to the actual collector, not manifolds with short runners leading into a single pipe riser will make more torque and more horsepower on a naturally asspirated motor. On a supercharged/blower motor thats not the case. The difference in these header/manifold header systems is "COST". Some are in stainless ie. CMI, Stellings, Hardin, etc. and some are cast ie. Kieth Eikert, Dana, Imco powerflo, and Stainless Big Torque three. For the most part both of these types of actual tube header/manifolds will produce 30-55 hp on big blocks over stock exhaust with retuning air/fuels in some cases. The cost differences here are roughly between $2500 to $5000 per set. The polished stainless units are usually at the top of the price range along with Kieth Eikerts and Hardin and the Dana flo-torques at the bottom.
Almost all the other exhaust aftermarket manifold replacement systems, ie, regular Stainless Marine, Imco (standard), Gil, Eddie Marine, Kodiak, etc. are cast manifolds with short runners merging into a common opening under the riser and with their improved runner size and riser diameters and in some cases riser length produce results better than most stock manifolds, not huge gains! just reasonable
15-30HP gains on average and their cost is generally in the $2000 to $2500K range .
Lets face it, you want more, THEN BE PREPARED TO SPEND MORE! Their are no cheap free deals in high performance!!

As for reliability and use, again here is a difficult area to always pin down! All headers and manifolds have a useful life and it generally depends on use, enviroment, care and installation. Take any good Marine high performance part or system, install it wrong, use it wrong, abuse it or ask it to last forever and your gonna get into trouble!! On the most part the manufacturers of todays high performance marine exhaust systems go to great expense, time and efffort to make sure their products are defect free and troublefree for their intended uses. Are they perfect! No! Just good stuff that when understood and properly applied and used will help make your performance boat run better, look better and add real value to your boating investment.

Rejoice in the fact you as boaters have so many good companies making such products for you that the choice of which to use becomes difficult sometimes. Don't bash or critisize so quckly when offering opionons and expierences with products. Realize that sometimes there may be some problems with any products, especially when it comes to performance marine systems. Also remember that these manufacturers are constantly improving their products with changes that generally come from customer issues and feedback!
I thought i would just try to offer some facts and information about marine high performance exhaust systems to interested fellow OSO'ers. Yes we have real working knowledge becuase we have tested and run so many we think we have a pretty good understanding of the differences in both construction and design as well as actual performance testing on 496 motors. I hope this sharing of information on exhaust will be helpful to readers of this thread.

Best Regards,

Ray @ Raylar

Thanks Ray.

I have a similar problem as the thread starter. I had gils on my engine. One of the gils leaked and caused reversion a couple of the cyclinders. (they still looked brand new from the outside, but we found the corrosion when we removed them).

I'm finishing building a new 540 to replace the old 454 and need to decide what to do for exhaust. I still have the gil risers which are in perfect condition. So do I buy new gil manifolds and save some money. Or do i go another route since the gils caused my woes in the first place.

Bottom line, is it worth the extra cost to go to headers? Not really looking for extra hp as the engine is already an overkill. Looking for long-term dependability.

i would go with the 5 year warranty and the exaust that every body is happy with (stainless marine)