Want to replace the stock cast iron manifolds on my 496 HO. Looking at Dana's w/ vortex risers, IMCO powerflows, EMI Thunders, Stainless Marine, etc.
Don't think I want a tubular welded header like Lightning. Would like to be able to still retain the stock Corsa Quick & Quiet system.
Any experience with which one sounds the best? They all appear to add 20-30 hp realistically although most claim 10%. The added power will help me run the next size prop I just bought, but I want it to sound louder too.

All of them are good choices. I've personally run Stainless Marine 4-5 years ago on 496's. Now I have Dana manifolds and I am pretty happy. I ran them on my engines when they were lightly modified and they added a little torque and the top end was maybe 1 or 2 mph at the very best.

If you want loud, go to the Dana website and look for the longer extended risers called 105's. You can run these for only a few $ bucks more or add to them yet another 5 inches and you will be dry to the transom. Even stock 105's, you are only 6 inches from the thru hull tips so they are mostly dry/or at least "dry" furthur back than some tubular setups. This is where you'll get your "loud"request since it doesnt mix with water till its wayyy back there. I added 5 inches to the 105's and my boat is really loud and realistically, too loud...

I understand longer, dry to the end risers would be the loudest, but I would like to retain the Corsa switchable option.
Not for me, but for resale I like every factory switch and option to work. Really just trying to decide if its even worth doing.
I'm going to swap out the water pump to a Hardin Marine SS unit, and thought it would might make sense to do it all at once.
Would the water pump be easier to access with the manifolds removed?

You can use stock Dana's and the sound might be a hint more throaty. On a single it wont make a difference if the manifold is off. The stainless pump is nice but for $99 you can buy the rebuild kit with the stainless inserts from R&R Industries. I've been running mine for 100 hours.

Check these out , great price . http://www.diamondperformanceparts.c...cat=282&page=1

Doesn't say they are for the 496. The KE website doesn't show them anymore and CP Performance has dropped them too.
Are they selling left over closeouts, or is this product still being produced I wonder.

Yes they are still being produced . Diamond Performance is an advertiser here and has purchased the design . Give them a call and they will fill you in as to application .

They are the baddest a$$ manifolds - always loved them. The problem with 496 is the temp sensor on the exhaust and the oil cooler mount. You can fab a mount and relocate the oil mount but the temp sensors have to work correctly or it wont run.

Ask me how I know this... LOL

I ran the KE's on one of my boats and they are noticeably louder than a Stainless Marines that they replaced, but you will never get them to work with a switchable exhaust set-up. They are just to long, even if you cut the tail's they are still to long. I'd stick with what you have, for a touch more power remove the tabulators, but I think that is only good for 8 hp. For extra speed you're better off getting your prop labbed. It's cheaper and will yield better results than new manifolds. The 496 manifold is pretty good.

Im confused, you want a louder exhaust but want to retain the silent choice? lol

Theres a couple ways to increase the decibel level. Reducing the amount of water in the exhaust, or build some high compression, big cammed, ported head engines.

I have Stellings headers with full dry 4.5 inch tails. Thank god I have a swim platform, otherwise it would be almost impossible to talk while idling around. Have you considered keeping the 496 exhaust, having custom dry to the tip tails made, and then add clamp on switchable mufflers at the end? Many times its not the exhaust itself that hurts power, its the amount of water in the exhaust that does. The exhaust pipes when filled with large volumes of water, not only reduces noise, it also reduces the volume of the pipes that can carry the exhaust gases.