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drh

Installing Slip in Exhaust Silencers

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drh

I've realized that while the straight through exhaust on the Sportster sounds nice, it would also be nice to be able to carry on a conversation inside the boat while underway or hear the music inside/behind the boat without blasting it. I've done some looking around here and I think I've settled on installing these 4" slip in silencers: http://www.cpperformance.com/p-12622-4-slip-in-silencer.aspx

I think I remember reading that @Woodski has this set up so I'd be curious on feedback from him or others how much these actually silence the exhaust and what is necessary to make this work. Also, I couldn't find specifics on the diameter of these silencers - I know sometimes 4" doesn't always mean 4" exactly.

Thanks in advance for any suggestions.

 

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Woodski

@drh:  What?  Sorry couldn't resist. Do you currently have a straight through system w/o any muffling?  What are your tips? 

The slip in silencers work quite well, slightly less sound suppression compared to a Primex fiberglass (original) muffler but not really very noticeable.  Actually, the biggest difference is not really between the fiberglass silencer and the slip in, it is the difference in the stainless tip v the original plastic tip with the rubber baffle.  What I did was add a rubber baffle to the 4" stainless tip, that made the most noticeable difference as my tips are straight ones (the turn downs were not offered at that time).  They are very close to 4" diameter IIRC, I did a whole home made exhaust system, the outlet at the riser is 4" all the way to the tips.  Slip ins + rubber baffles are all the sound suppression I use.  Boat sounds slightly different to others but not really louder (different because my engine is not stock compression ratio so it changes the tone).

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drh

Haha funny man...yes I have straight through exhaust without any muffling and the straight black plastic tips with rubber baffles. Are you saying that the stainless tips are louder that the plastic because they didn't have a baffle originally?

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Woodski

@drh:  Correct, the stainless tips do not have rubber baffles, most have a swinging stainless steel anti surge (or back flow) device that does not do as well a job with noise suppression.  The rubber baffles do a good job of noise absorption due to pliability and material.  I added a rubber flapper and was surprised at how well it reduced the noise level, pretty simple to construct using a PVC ring as the attachment device.

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drh

So given that I have the rubber baffles already will I notice much difference with the slip ins? They claim noise reduction of 8-10db.

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Chaabo

Did you look at this thread?

Looks like your best option here.

mf_3.jpg

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drh

@Chaabo: No I haven't seen that. That's almost exactly what I was thinking; thank you. I wonder it if wouldn't be too difficult to fab up something like those canisters myself with either ABS or PVC pipe and fittings? Looks like they have the same slip in silencers inside.

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oldjeep
2 minutes ago, drh said:

@Chaabo: No I haven't seen that. That's almost exactly what I was thinking; thank you. I wonder it if wouldn't be too difficult to fab up something like those canisters myself with either ABS or PVC pipe and fittings? Looks like they have the same slip in silencers inside.

Those are exhaust pipes, pretty sure ABS/PVC would be a really bad idea.

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Chaabo
1 hour ago, drh said:

@Chaabo: No I haven't seen that. That's almost exactly what I was thinking; thank you. I wonder it if wouldn't be too difficult to fab up something like those canisters myself with either ABS or PVC pipe and fittings? Looks like they have the same slip in silencers inside.

Problem is - inner hose diameter is 3.5 the slip in's are for a 4 inch ID application.

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drh
On 6/24/2017 at 9:10 AM, oldjeep said:

Those are exhaust pipes, pretty sure ABS/PVC would be a really bad idea.

You're right. I guess I was thinking CPVC or whatever material is used for hot water supply. I think it would be more trouble than it's worth though. I'll probably go with the stainless option from Eddie Marine.

Any suggestions for cutting the exhaust hose? Could I cut it in the boat or should I go ahead and take it out? I was also thinking of putting some material between the stainless and bilge to prevent vibration.

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Woodski

@drh:  Actually not a bad idea IMO, seems works just fine.  500 hours and going strong on my home made exhaust system.  You can get the black ABS pipe and simply bolt the slip ins in the pipes.  The ABS has a higher melt temperature than rubber hoses from exhaust manifolds to the pipes themselves and it won't collapse.  The 4" ones fit in the pipe just fine, you will need some reducers to match to rubber hose on each end.  There is plenty of cooling water running through the pipes, you can rest your hand on them all the time.

@oldjeep:  why are you thinking a bad idea?

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oldjeep
9 minutes ago, Woodski said:

@drh:  Actually not a bad idea IMO, seems works just fine.  500 hours and going strong on my home made exhaust system.  You can get the black ABS pipe and simply bolt the slip ins in the pipes.  The ABS has a higher melt temperature than rubber hoses from exhaust manifolds to the pipes themselves and it won't collapse.  The 4" ones fit in the pipe just fine, you will need some reducers to match to rubber hose on each end.  There is plenty of cooling water running through the pipes, you can rest your hand on them all the time.

@oldjeep:  why are you thinking a bad idea?

ABS max operating temp is 180F and PVC is 140F in a non pressure application.  And ABS tends to get more brittle over time, which is not great in an environment where there is heavy vibration like an exhaust.  The cheap exhaust hose is around 250F max temp and the good blue stuff is 350F

Edited by oldjeep

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Luckylindy

When I bought my '99 Sportster I couldn't stand how loud it was. I know it sounds ghetto but I found a 4" clay to pvc rubber boot and a 90* pvc elbow on each tip to do the trick. The boot goes around the stock tip and has enough room inside to clear the stock flapper and the elbow directs the noise down so way quieter. The only issue is it has a little spray off the tip, I tried to cut them down and ended up cutting too much off and it got noisy again. I put new elbows on but haven't trimmed them to reduce spray yet. Will post a pic tomorrow if anyone is interested 

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Michigan boarder
5 hours ago, Luckylindy said:

When I bought my '99 Sportster I couldn't stand how loud it was. I know it sounds ghetto but I found a 4" clay to pvc rubber boot and a 90* pvc elbow on each tip to do the trick. The boot goes around the stock tip and has enough room inside to clear the stock flapper and the elbow directs the noise down so way quieter. The only issue is it has a little spray off the tip, I tried to cut them down and ended up cutting too much off and it got noisy again. I put new elbows on but haven't trimmed them to reduce spray yet. Will post a pic tomorrow if anyone is interested 

I'm very interested!

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Michigan boarder

Here's my exhaust build, did this a few years ago.  ETX manifolds into silicone elbows, into a Silent Rider with the guts removed, into wet exhaust hose, into PVC elbows, into wet exhaust hose, into STE's.  Sounds fantastic, quiet inside the boat with a nice rumble on the outside.

Exhaust complete compressed.JPGExhaust 45 degree elbows.JPGSTE installed 002 compressed.JPG

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Luckylindy

https://vault.myvzw.com/webcs/app/share/invite/Bl9dznIclE

https://vault.myvzw.com/webcs/app/share/invite/YIYlQ7t85l

The boot is a 4" clay to 4" pvc. The elbow is a 4" to 3" street elbow after slipping the tip into the boot a added a few screws through the boot before the clamp went on the help hold it in, not sure if it was necessary, but it made me feel better. I considered using a 4" both end elbow but thought the 3" tip looked less bulky and the hole in the existing tip is only 3" so I knew it wouldn't choke the flow. The way these are now there is a bit of spray off them. I had a set before that i trimmed the last 2" or so step off of to get rid of the spray, but it made it louder so I replaced them and just deal with it , it's really not that bad.  

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Luckylindy

Also I will add, i had to shave the boot where it goes between the tip and the wedge bracket. It is very thick and i had to make it thinner to fit between. Also yes i know the pitot tube is broken. As soon as i bought the boat I added marriage saving Stargazer perfect pass. I plan to add underwater lights where the pitot tubes currently are, just haven't done it yet. it may not be the prettiest way to quiet the boat, but it took like 30min and is very effective, much more pleasant in the boat now and dont need to turn the stereo up nearly as loud to hear it

 

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UWSkier
On 6/30/2017 at 6:44 AM, Michigan boarder said:

Here's my exhaust build, did this a few years ago.  ETX manifolds into silicone elbows, into a Silent Rider with the guts removed, into wet exhaust hose, into PVC elbows, into wet exhaust hose, into STE's.  Sounds fantastic, quiet inside the boat with a nice rumble on the outside.

Exhaust complete compressed.JPGExhaust 45 degree elbows.JPGSTE installed 002 compressed.JPG

I've often wondered if the v-drive style silentrider could fit under a dogbox.  That's where the ECM sits on the Monsoon.  Would be awesome if it could though.  They're nice and quiet.  I love the sound of our VLX.

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Luckylindy

P.S.S I just realized those eddie marine mufflers are a PAIR for $139. At $280 i wasn't interested but for 139 i may still add something like that. the boat is fine the way it is, but as a boat mechanic I hear boats running ALL DAY and i don't need to hear mine when I'm NOT working.  

 

Edited by Luckylindy

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solorex
On 6/30/2017 at 4:44 AM, Michigan boarder said:

Here's my exhaust build, did this a few years ago.  ETX manifolds into silicone elbows, into a Silent Rider with the guts removed, into wet exhaust hose, into PVC elbows, into wet exhaust hose, into STE's.  Sounds fantastic, quiet inside the boat with a nice rumble on the outside.

Exhaust complete compressed.JPGExhaust 45 degree elbows.JPGSTE installed 002 compressed.JPG

Will these manifolds fit on my 350 Mercruiser (non-vortec 1997) in my Tantrum?  Any clearance issues since mine is not an Indmar?  My manifolds are due to be replaced... these seem to be well priced without having to spend $2000+ on stainless marine manifolds etc...

Edited by solorex

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Michigan boarder
19 hours ago, solorex said:

Will these manifolds fit on my 350 Mercruiser (non-vortec 1997) in my Tantrum?  Any clearance issues since mine is not an Indmar?  My manifolds are due to be replaced... these seem to be well priced without having to spend $2000+ on stainless marine manifolds etc...

I think they should.  The heads on mine were replaced with the engine rebuild, can't recall what we went with, but they are a Vortec head.Valve cover clearance.jpg

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solorex

Hmm... thanks I am sure Bakes will know.  I assume I don't have a Vortec, mines a 1997 boat with the Magnum 350.

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Michigan boarder
30 minutes ago, solorex said:

Hmm... thanks I am sure Bakes will know.  I assume I don't have a Vortec, mines a 1997 boat with the Magnum 350.

I thought everything was Vortec after 1996? 

I agree, check with Bakes.  I would also assume that if they don't fit Bakes would take them back as a return.

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MadMan
23 hours ago, solorex said:

Will these manifolds fit on my 350 Mercruiser (non-vortec 1997) in my Tantrum?  Any clearance issues since mine is not an Indmar?  My manifolds are due to be replaced... these seem to be well priced without having to spend $2000+ on stainless marine manifolds etc...

I would think those manifolds would fit every small block Chevy since 1955.

The exhaust flow in those manifolds are like tri-y headers form the '60s.  A reason for the tri-y design is to split up the exhaust flow between cylinders 5 & 7 since they are back to back in the firing order.  Indmar didn't do this on their design, 5 & 7 are on the same Y.

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