2001 Stock 502 OM series motor.
OK, we have three major upgrades this winter once the boat returns, We will leave #2 and #3 upgrade alone at this point.
I am ready to purchase my exhaust.

I have read for two weeks, every post on the net, especially here on OSO on exhaust and now some new questions come to light today.
My motor head friend says "On the Stainless Marine's short SS risers you still get some reversion on the back two cylinders, minimal but there... spend the extra $175 for the long risers." Fact is that could be there now with stock risers for that point.
I called IMCO for their sales pitch, they agreed even in their own product (PowerFlo's) can have the same issue with short risers. IMCO swears to no welds, their claim to fame, they even told me their cheapest retailer (Teague, they buy volume).
Stainless Marine swears to their never failed 5 year warranty, but when you read their warranty, reversion is NOT covered even if caused by their exhaust, you need a law degree for their warranty.

ABOVE WARRANTIES WILL NOT APPLY TO
1. Haul-out, launching, towing, storage telephone or rental charges, loss of use, inconvenience, etc.
2. Removal or reinstallation.
3. Incidental or consequential damage, including but not limited to reversion and water ingestion.
4. Misused, abused, altered, or improperly installed equipment, of failures caused by third party repairs.

SO, Question is:
If I buy the short SS risers do you guys feel the back cylinders could be in jeopardy over time? And if Pro Charged does that change your thought process on which you would choose of the two? RISER Lengths?....
I am Through hull and can go longer on the SS risers in length if it will positively avoid a possible reversion issue.....
Looking for thoughts basically on the reversion possibility on short SS risers, like the ones QQuiet guys use, I would use them and hose to the transom..
I have an unheard of price on a set of each, saving about $400 each over net pricing, including all relocating hardware for the oil filter and all brackets, brand new, SO I am wondering before I mail a check.
Please give technical reasons in your replys, so I might throw them out to the manufactures before I make a decision.
I can stroke a check on the dumbest stuff easily, but on uneducated stuff I tend to be cautious and ask allot of questions....
Thanks, in advance....
Bryan

PS CMI's and other true headers are not affordable for me.

Hey Bryan,

I'm sure you must have seen my post re: questions about exhaust as well. I am interested in what you find out.

Before you go to upgrade #2 or #3 (if either is a charger) send me a pm or e-mail. I have put on an "Extreme Supercharger" from Livorsi Marine (Gaffrig) and I am extrememly pleased with my "new" Donzi. Even during the hotter months of summer I was able to get 77mph/gps out of the boat. We have put 170 hours on motor since charger.

Good luck on the upgrades. Get in touch if you want more info.

Tim

Bryan,
I did LOTS & LOTS of homework before I bought an exhaust for my old boat. If I did it again, I'd save up for REAL headers, it's only about $400 more. THEN you'd have some performance gains.
Don't know if you remember, but my gains vs money spent, wasn't worth while.

Yes I got SMALL amounts of water (back port cylinder) but I (nor the merc tech) don't think it was from reversion. More like condensation.

Good Morning Bill:
We had a great time last night, the seafood was unbeliveable!

Exhaust; I am looking at the Stainless Marine with the full stainless (long) riser now, I can't get into CMI's for a couple thousand. I can get these from a friend at a great price new.

Talk at ya later........ Bryan

It seems that all anyone talks about is performance gains or horsepower with aftermarket exhaust. For me, there were several other considerations. I opted for Stainless Marine long through transom risers. My engine builder detailed to me the chances and perils of reversion with the cam profile he chose if we did not address the risers. He really wanted me to go to CMI's but we ended up with Stainless Marine. There are many weak points in the stock system. Water through the flange between riser and manifold is one big point. The life of regular cast steel versus Aluminum and Stainless steel is certainly another. Weight is another. Performance is another. Longevity is another.

The Stainless Marine setup I ended up with was much lighter than the stock Merc stuff. It also will most likely last the life of the boat. That is something many exhaust system will not do. In my
opinion it looks pretty good too. Maybe not as cool as a set of tube CMI's, but still nice.

For me, the absolute trouble free operation of my Stainless Marine exhaust for over seven years is worth the slight difference in performance some other tube type systems might offer. In a 10,500 pound boat, how much difference will 30 or even 50 horsepower make ?

Not much !

I have enough things to work on with twin BBC and all the other maintenance items a boat comes with. For me, a no maintenance exhaust system is worth its weight in gold.

Bryan,
I think that worrying so much about reversion is a little premature without knowing the camshaft specs. If you have a supercharged engine everything is changed. Remember that reversion is caused by the exhaust valve being open when the intake valve is open (valve overlap). The intake manifold vacuum pulls the water into the exhaust port and the cylinder. With a supercharged engine you have positive pressure at the intake valve from the blower boost (you may have a little vacuum at idle but a lot less than a naturally aspirated engine). The beauty about superchargers is that you don't need a huge camshaft to make power (all you need are large intake ports). If you run a single pattern camshaft (same intake and exhaust duration) with a wide lobe separation angle (114-115 degrees) reversion isn't much of a problem with a blown motor. Hate to skirt your question about manifolds but what is the camshaft going to be? What is the compression ratio and how much boost are you going to run?
It is the same old adage, "It all must be a combination of correctly matched parts to get a good running engine."
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

What Dennis said. I run Gils with Silent choice and pick my cam to match the exhaust. Cant/Wont go to a bigger cam. You should post your cam specs and whether or not your gonna "blow" the engine.

These exhaust will go on a new Merc Gen VI 502 with 150 hours on it, totally stock, eventually procharged.
Thanks for the great info thus far.
Bryan

Bryan,
If you are going to use the stock camshaft (good choice) then I think you should go with the most economical exhaust system. I don't think you have anything to worry about!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Thanks Dennis, I am ready, just trying to decide if I want the longer custom fit long risers or the stand short risers on my Stainless Marine system.

Like I said the motor is stock in a 2001 26ZX Donzi, do you feel the shorter SS Risers will be fine also running a procharger? I hate to spend the extra $200 if not need.

Thanks, Bryan