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Old     (bigshow)      Join Date: Feb 2005       05-09-2008, 7:55 PM Reply   
I really miss my Fresh Air Exhaust. It worked well and significantly reduced noise. My new boat has Side Swipe (SS). SS also works well, it reduced CO exposure and exhaust smell. However Side swipe is too noisy for my tastes. So after some research I found a ďSilencerĒ that will easily fit inline between the SS control valve and flapper valve. Take a look at this link:

I installed the silencers on the starboard side this evening and I brought home a sound level meter from work.

It took all of 30 minutes to install one side. That's largely because I didn't know what I was doing and because I made several trips to the basement for tools. I used a large standard screw driver, I had a large Phillips screwdriver that I didnít need, and I used a coping saw.

Removing the old hose between the exhaust valve and the flapper valve was easy, just loosen four band clamps. I rolled the exhaust hose back and forth and pulled on it until it came off.

I removed the four screws on the SS flapper valve, the valve seen on the hull of the boat. It turns out I didnít need to remove the screws, I never removed the flapper valve.

The silencers are 5 inches long with a 4 inch diameter. I cut off a 4 inch long section of exhaust hose. I placed the silencer and 4 inch hose near the flapper valve. Then I laid some hose next to the silencer and the Side Swipe switched exhaust valve to see how long the other section of hose should be. I cut to fit, slid this longer section over the silencer and pushed the hose on until it went back over the SS switched exhaust valve. I had to add four new band clamps. I tighten up the band clamps and the starboard side was done. No big deal really.

Iím taking the Mighty Enzo to the Crush the Ice for Life event in Rome City Indiana tomorrow. I only installed the silencer on the starboard side so Iíll be able to compare the port and starboard side with the sound level meter. After that Iíll install the silencer on the port side.

I spent $119 plus shipping on the silencers. I spent another >$40 on extra 4 inch hose and band clamps. This addition is well under $200 and very easy to do. Iíll report on the noise improvement soon.

The silencers and new hose... Cutting a 4 inch section

The cover over the SS and the old hose

The finished conversion

Disclaimer: Iím not connected to Rex Marine, marine exhaust hose manufactures, or band clamp manufacturers. Fresh Air Exhaust donated a system to the 2007 Scioto Wakefest. I have received event funds from Centurion Boats which have been used to operate wakesurfing competitions.
Old     (surfdad)      Join Date: Sep 2004       05-09-2008, 8:31 PM Reply   
Nice mod Ed...I'll keep my fingers crossed that it reduces the noise substantially!
Old     (smedman)      Join Date: Feb 2006       05-09-2008, 8:33 PM Reply   
Ed - You are a mad scientist!! Never satisfied with the status quo. Excellent! I love it!!

Are the silencers specifically for the Sideswipe? Or just exhaust in general?
Old     (enzostyle)      Join Date: Aug 2006       05-10-2008, 7:46 AM Reply   
Ed what are you thinking? You can't just leave us hanging like that. I want results now dang it, I am no good at waiting.

Couldn't you run it on a hose and at least give us a preview of some @ idle db levels?
Old     (enzostyle)      Join Date: Aug 2006       05-10-2008, 7:54 AM Reply   
I wouldn't be so impatient if my season could get started. Because of all the rain we have been getting my lake has a no wake rule in effect cause of high water.

My dock and lift have been in the water for 3 weeks but the boat is still in my drive way. The forecast is not looking much better for the coming week either.

Good to see some of you are out riding, but it makes my wait all the more painful!
Old     (t_mann)      Join Date: Mar 2008       05-10-2008, 9:56 AM Reply   
Show Great idea. We sell a ton of side swipe but the noise is the one negative that it has. We have been trying to get Centurion to make a side swipe system that could run exhaust out the transom when your not surfing. Let us know how your system reduces the noise level and if you see any performance decrease because of the back pressure. If it works well I will be the first to talk with the factory about adding it to the boats, or at least having it as an option our service dept can install. Once again great idea.
Old     (bigshow)      Join Date: Feb 2005       05-10-2008, 8:29 PM Reply   
A very big disappointment.

There was no, noticeable difference in measured dB levels. None!

I brought a clipboard and was going to do some formal measurements. However, I didn't spend a lot of time testing with the dB meter. In fact we were closing out the day at the Crush the Ice for Life event in Rome City, Indiana. We were trying to recover the boat before the rain hit and so made measurements on the way back to the boat ramp. So my measurements were ad hock. Since we we're rushing I didn't take notes. I'll repeat this test and record the results.

Some of the folks on shore at the event thought that the sound was cool. Some of the young surfers on the boat also thought the loud sound was cool. I do not, my head rings. I really miss my FAE.

The boat had no ballast and only had a crew of two. I located the dB meter at the ski pylon and pointed the mic upward. We tested at 1,000 rpm, 2,000 rpm, and 3,000 rpm. Sound levels at 1,000 rpm were about 85 dB, over 90 at 2,000 rpm, and high 90s at 3,000 rpm.

My driver thought it sounded different form side to side. I pointed out that the drivers seat is asymmetrically located so naturally the sound level is different from side to side. I move the dB meter right by the drivers head. Again I pointed the mic on the meter upward. No difference in dB levels were measured.

Subjectively I'd say that the port and starboard sound different, but not much. I got confused a few times when the switch was thrown. By ear I couldn't tell the difference. So I'd say that there isn't a strong difference with the "Silencer" installed or not installed. The note of the system sounds different.

There are other muffler options for inboards but the layout of the SS doesn't appear to have the dimensions needed to accommodate them. I think that it should be possible to reduce noise with some sort of muffler. This isn't it. If it were designed in there should be more opportunities for reduction of noise.

Jason, Sorry to keep you hanging but I did the install after work, in the rain, and I was planning on abandoning the family all Saturday. So once I had the "Silencer" installed I spent a little quality time with my wife. She let me talk her in to buying the boat so you have to take care of girls like that:-)

(Message edited by bigshow on May 10, 2008)
Old     (enzostyle)      Join Date: Aug 2006       05-12-2008, 8:16 AM Reply   
That's too bad that didn't work out. I was really hoping you had a solution.

When I got my first Avalanche with sideswipe we were really into wakeboarding. After every outing I would have to suffer through my ears ringing as I am sensitive to loud noise. My wife would ride in the bow when we were up and running to avoid the noise.

Now that I am mostly surfing It doesn't bother me. My lake is small enough that we do not have to run on plane to get anywhere. I just run the exhaust out the port side so it is below the waterline till we start surfing.

When I need my wakeboard fix I just ride behind my friends non-sideswipe avy.
Old     (norris_laker)      Join Date: Aug 2006       05-12-2008, 8:52 AM Reply   
Hey Ed,

Is the solution to problem to do what Jason does? Run the exhaust out the side that is weighted down. I know that defeats the purpose of sideswipe but I think sideswipe is at best an OK idea with poor implementation. Would running the exhaust out the weighted side give you the same effect as Fresh Air? To date I'm not aware of any surfers that have been over come by fumes while surfing. The biggest problem is for people that hang out by the back on the boat near the exhaust. Besides the loud noise, my biggest complaint with side swipe is the tremendous amount of fumes that get blown back into the boat when the boat stops and turns to pick up the rider.
Old     (bigshow)      Join Date: Feb 2005       05-12-2008, 9:28 AM Reply   
Roy, I think he meant to only do that while driving back to pick up a rider.
Old     (enzostyle)      Join Date: Aug 2006       05-12-2008, 12:03 PM Reply   
I only do that while we are idleing around. If you exit the exhaust to the surf side it creates a ridge about half way up the wake that is very annoying. At surfing speeds the exhaust noise really isn't that much of a bother. It's the on plane cruising speeds that can get to you.

I love the sideswipe option, but like I mentioned befor, I don't have to go far to get to our riding area. When we don't have a rider in the water, my boat rarely makes plane. When we go out for "social hour" we just puts around.

(Message edited by enzostyle on May 12, 2008)

(Message edited by enzostyle on May 12, 2008)
Old     (deltaboy)      Join Date: Jan 2007       05-12-2008, 1:12 PM Reply   
Show we have a similar set up to the side swipe and when demoing the boat it was the only concern for me (the noise) especially for those sitting in the rear. I researched it and came up with a company that I think has since gone out of business HPI Silencers. They were or are suppliers of smaller exhaust parts for some of the Merced area manufacturers (Malibu, Fineline and possibly Calabria). Anyhow they colaborated with Pleasurecraft to make sure the restriction created was going to work within the tolerances set by PCM. They made a set of silencers similar to what your set up requires but they were too quiet (I wanted a little more rumble) so they said cool send em back and we'll make up another set and if you like em pay for em. They got it perfect the second set. Anyhow you may look em up they may still be around and willing to do the same for you. I think the cost was about $200 or $250. All made from stainless steel as well. You can hear them on youtube just type in wakecraft and we have some crapy video someone else asked for so they could hear the boat after the silencers were installed. Shoot me a PM if you have any questions. Sorry about the spelling im in a hurry.
Old     (bigshow)      Join Date: Feb 2005       05-12-2008, 6:59 PM Reply   

I heard that HPI designed and fabricated Side Swipe for Centurion, or maybe they just fabricated it. Any way I tried to look them up online but couldnít find them.

You can find other exhaust systems for inboards. Overtonís sells a system. Those systems are shaped like a snake eating something bigger than they are. Big in the middle and narrow at the ends.

There isnít any clearance at the flapper valve below the tube. Any other solution would have to move the muffler away from the flapper. My local dealer, no longer a Centurion dealer, said that he had a client with a son that had a hearing problem. The noise made his son ill. He said that he found a way to put a muffler on that boat. He also said that it was a bear to install and that he wanted $1,400 for the job. Thatís too step for me.

Iíd be interested in a solution but gas prices are kind of tapping my discretionary resources.
Old     (riverdog)      Join Date: Dec 2004       05-12-2008, 7:46 PM Reply   
How can the add claim 8-12 db reduction. Seems like false advertising. You would expect some sort of db reduction. I'd call and get my money back. It is a shame it didn't work.
Old     (tonyv420)      Join Date: Jul 2007       05-13-2008, 2:18 PM Reply   
Cant you go back to your FAE?
Old     (rallyart)      Join Date: Nov 2006       05-13-2008, 2:39 PM Reply   
Show, if you wanted to fidget, a lot, you could rig up something with Supertrapp plates to reduce noise significantly.
Just an idea and I don't know how I would do it but they have 5" and 4" systems that don't take much room and you trade off flow and noise level by adding or subtracting plates.
Old     (bigshow)      Join Date: Feb 2005       05-13-2008, 6:29 PM Reply   
Anthony I'd have to sell my boat and buy another without side swipe.

I have no idea what Supertrapp plates are. I've got a busy schedule I'm not sure how much time I have to fool around with another idea. I wonít have time for something like that until the fall.
Old     (surfdad)      Join Date: Sep 2004       05-13-2008, 6:53 PM Reply   
Killer exhasut system. The disc's at the end of the slip-on help quiet the exhaust note...but I do believe that Super-trapp's use a packing material inside that would get destroyed when "submerged" in water. I could see that as possible when listing and the engine is off. Most of the silencers for my dirt bikes all had this same packing - looks like fiberglass insulation. Very efective at quieting the exhaust note.

Old     (bigshow)      Join Date: Feb 2005       05-13-2008, 7:29 PM Reply   
Jeff, the coolant also goes out through the exhaust so glass would get wet anyway. I'm thinking about putting two of these silencers in line.
Old     (surfdad)      Join Date: Sep 2004       05-13-2008, 7:55 PM Reply   
I thought about that after posting! I don't think you can use any of the silencers that use the glass packing.

Two inline of the first ones you showed?
Old     (bigshow)      Join Date: Feb 2005       05-13-2008, 8:15 PM Reply   
The SS system has a kind of flapper valve. Traditional inboards also have flapper valves. It seems like a lot of Malibuís have turn downs. I donít think they have flapper valves. Fresh Air Exhaust has a down pipe and no flapper. All of these systems do something to with preventing water from backing up in to the engine, right?

Pushing water back up the engine might be possible when turning a SS equipped boat, I suppose?

You could keep a flapper and pack the tube with those super trap plates.
Old     (bigshow)      Join Date: Feb 2005       05-13-2008, 8:18 PM Reply   
I' sure there's enough room for two. The hose sections will be short. It will be hard to get the hose over without removing the flapper valve. I removed the mounting screws for the flapper last week. I pushed on the valve a little but it didn't budge.
Old     (riverdog)      Join Date: Dec 2004       05-13-2008, 8:55 PM Reply   
Hey Show ,would it possible to install before the ss after the manifold. Wonder if that would make a difference?
Old     (rallyart)      Join Date: Nov 2006       05-13-2008, 10:03 PM Reply   
Most of the Supertrapps can be disassembled to repack them. If you take out the fibreglass packing and repack it with stainless steel wool it would have some of the affect. You can also just use the plates with no tube. They can bolt onto a flange attached to anything.
I've run Supertrapps mufflers with plates and also just run plates on racing systems.
Old     (bigshow)      Join Date: Feb 2005       05-14-2008, 5:04 AM Reply   
Scott, it looks possible to put the silencers in just after the manifold but I think it would be a lot of work, might have to remove manifolds first. That's not too big of a deal I don't think.

I'll have to look in to the suppertrapps. I emailed them last night.
Old     (tonyv420)      Join Date: Jul 2007       05-14-2008, 10:52 AM Reply   
Yea I didn't think of that. My Bad.
Old     (surfdad)      Join Date: Sep 2004       05-14-2008, 12:27 PM Reply   
Art - I didn't realize there was SS packing - just did a search and it's cheap like 9.95. The blurb indicated it was unaffected by heat and absorbed more db's that 'glass. I've used steel wool before and that looks like it actually burns. :-)
Old     (rallyart)      Join Date: Nov 2006       05-14-2008, 12:52 PM Reply   
Ultramax used to make a 5 inch full race muffler with stainless packing. Maybe they still do.
I watched dyno runs with a straight pipe on the headers, a Flowmaster, and the Ultramax on a 750 hp GT V8. The Ultramax had the most power and was the quietest.
The quality of the stainless makes a difference in how long it will last as does it's minimum gauge.
Of course the trick on a boat is getting all the water out, or designing it so it won't pool in the muffler.
Old     (bigshow)      Join Date: Feb 2005       05-18-2008, 1:44 PM Reply   
It's cold and windy today so I canceled my crew. I did go over to the Mighty Enzo with the other "Silencer", band clamps, hose, saw, and a screw driver. I cut off an inch of hose between the SS valve and the tube that joins the left and right exhaust. Then I stuffed both "SilencersĒ in the hose between the butterfly valve and the SS valve. I connected the whole thing back together. So now I have two "SilencersĒ on the starboard exhaust. Iíll have to wait until next weekend to see if two in series ďSilencersĒ has any effect.
Old     (bigshow)      Join Date: Feb 2005       05-23-2008, 6:32 PM Reply   
Looks like I need to buy two more:-)
Old     (rallyart)      Join Date: Nov 2006       05-23-2008, 7:09 PM Reply   
Old     (bigshow)      Join Date: Feb 2005       05-23-2008, 7:28 PM Reply   
I have two on the starboard side. By ear itís much more quiet. I'll measure dB levels tomorrow.

What's weird is that it's loudest with both sides open. Must be some resonance?

(Message edited by Bigshow on May 23, 2008)
Old     (surfdad)      Join Date: Sep 2004       05-23-2008, 9:14 PM Reply   
Ed, do the slip on's get hot at all? Just wondering if they would affect your ballast / bladder in anyway?

Congrats on getting it quite!
Old     (bigshow)      Join Date: Feb 2005       05-24-2008, 6:41 PM Reply   
They are more of a slip under rather than slip on. I havenít measured temperature. The exhaust exists with a lot of water from the cooling loop. I donít think the temps will ever reach boiling.

I did a little power experiment today. I got the Mighty Enzo running around 3,300 RPMs with the silenced exhaust. Then I flipped the SS switch to the other side. The RPMs climbed. Then I set the SS switch to both. RPMs climbed again. At the end I think it reached 3,800 RMPs but by ten we really got on plane. I think the only conclusion you can make is yes, there is come constriction and loss of performance. As long as Iím not hurting the engine itís worth it.

Iíll post the dB readings soon. The short information is that the levels are noticeably lower with the hush pipes.

(Message edited by Bigshow on May 24, 2008)
Old     (t_mann)      Join Date: Mar 2008       05-30-2008, 1:30 PM Reply   
Show Did you test the dB rating. I am dying to know.



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