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"Turn-downs" vs. Merc. Stage 1?

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Old 02-16-2010, 11:00 AM
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Default "Turn-downs" vs. Merc. Stage 1?

Just curious what peoples thoughts are in comparing the two of these to each other with regard to performance and effectiveness.

In looking at the Merc Stage 1 (essentially what NorTech offers and has made quite popular) it is basically an exhaust port exiting the boat under the water line. So, at idle it is like a traditional ski boat, and on plane - same set up - exhaust exiting above the water line. This allows a somewhat free-flow exhaust, albeit a 2-into-1 scenario, giving a reduction in noise around the harbor as well as on plane.

With the "turn-downs" you have a very similar over-all effect, below the water line at no-wake and above on plane, but with a 2-into-2 setup.

My question is - has anyone compared the two to see if there is a similar - equal - or disparate effect between them? Where as you have the option when building a new boat to go to the "Stage 1" style exhaust, if you buy a boat that is built without it, can you achieve the same effect with the turn downs? One additional side benefit would be - aside of no giant holes in your hull below the water line - you can pull the turn-downs off when running in a poker run or just off shore in general, if you wanted. Let's face it - as much as the noise police are clamping down, and a quieter boat is nice at times, who doesn't love the sound of good old fashioned thru hull once in a while!? And with states like NH outlawing any sort of "switchable on-the-fly" exhaust, I would think this option has some appeal? Put 'em on for some areas and take 'em off for others...
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Old 02-16-2010, 11:10 AM
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I have turndowns that I have used on my Tiger and am now using on my MTI.

This system is much more rudimentary than what Nortech installs and I imagine less expensive. I also think from having friends with Nortech boats with that system that it is much more stealthy than turn downs.

Also I would not put turndowns on a Nortech it would look a little weird I imagine.
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Old 02-16-2010, 11:19 AM
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I've only seen the Mercury exhaust on 1 boat. There are probably more, but I see turndowns all the time.
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Old 02-16-2010, 11:19 AM
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I run turndowns on my Skater and MTI. Very legal 86 DB on both at idle. The Nortech system is very nice but needs to be done at time of rigging and is expensive. The turndowns also direct the sound down at high speed but is still very loud. The sound seems to have less harshness that way. Not even close to being legal on a flyby test. Good thing is where we boat the big noise concerns are in the harbors and no wake zones.
CMI can make custom downturns for you. Call Ateco. ON the Skater I rigged the transom tips to exit underwater and have a slight downturn rather than go with the big downturns.
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Old 02-16-2010, 11:23 AM
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I used turndowns on my Ilmor 710 Lavey and loved them. I took them off for poker runs and any time I was up for "That" sound.

I found that the turndowns not only kept the noise low while off plane but the sound inside the boat was greatly reduced when running as well. That aspect could be boat specific but I'm going to use them on my new Lavey as well. I also had a set of Gibson mufflers and liked the trundown much better. Simple. Cost Effective.
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Old 02-17-2010, 09:56 AM
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This was the info that I was looking for... thanks guys! Basically, I was looking for first-hand experience on one vs. the other and if you went the turn-down route, would it be closely equivalent to the Stage 1 / NorTech set up?

I noticed in the pics of the new 1350 turbo Merc motor from the show that they are routing the tailpipes to exit down at the upper gearcase level, vs from the typical thru hull level. Clearly a nod to them meeting the stringent new noise laws that we are seeing, esp in EU.
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