Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Sign in to follow this  
Ndawg12

"under water exhaust" without Butterfly valves and Silent Rider

Recommended Posts

Ndawg12

The welders at my shop are just about finished with my newest version of my home made stainless steel "under water exhaust" .  I got to thinking that while I'm at it maybe I'd pull out the silent rider and run straight from the exhaust manifolds to the outlet ports.  The question is I don't have the butterfly valves between the outlet ports and the external exhaust assembly so I'm wondering if I shouldn't leave the silent rider in place as another obstacle for the backflow of water to navigate and prevent hydro-lock situation.

 

Edited by Ndawg12

Share this post


Link to post
kerpluxal

I would like to see pics of your FAE... and is it changing your wake up.. and more curious on higher speed.. like slalom speed ;)...

I am not an hydro engineer.. but to me I would think not... but again.. I could be very wrong.. It would seem there would be more exhaust pressure exiting out of and FAE then water pressure trying to come up the pipe... I know when you do not have a FAE or turn downs that you better have butterflies... but it seems that with all the external piping that it would be difficult to work it's way up.. How does Malibu do their new system with their surfpipe?

Edited by kerpluxal

Share this post


Link to post
Ndawg12
3 minutes ago, kerpluxal said:

I would like to see pics of your FAE... and is it changing your wake up.. and more curious on higher speed.. like slalom speed ;)

My first attempt dropped my speed by 2 mph max.  I threw it together quickly myself and used cheap muffler pipe knowing that some day I'd use it as a template for a nice stainless steel version that our company welders could fabricate in their down time.  Welders love tinkering around on stuff like this, I missed my calling :biggrin:

Share this post


Link to post
formulaben

I would think it would be quite difficult to get water back up in there all the way to the top of the risers.  Somewhere I read of owners removing the muffler and going straight to the FAE and it got even quieter.  I'm planning on doing the same, as it will open up some space and make impeller changes much easier.

Share this post


Link to post
Ndawg12

BTW it's not FAE, it's "under water exhaust" :biggrin:

Share this post


Link to post
Ndawg12
1 minute ago, formulaben said:

I would think it would be quite difficult to get water back up in there all the way to the top of the risers.  Somewhere I read of owners removing the muffler and going straight to the FAE and it got even quieter.  I'm planning on doing the same, as it will open up some space and make impeller changes much easier.

Excatly, and my reversibles are back there!!  Just seems like it would make a lot of things much easier.

Share this post


Link to post
kerpluxal

@Ndawg12 .. are you losing 2 mph due to exhaust restrictions or drag??? if to exhaust restrictions @formulaben will the removal of the silent rider gain back you lost restrictions? My answer is yes.. but I am not sure how restrictive the silent rider is...

Share this post


Link to post
kerpluxal
Just now, Ndawg12 said:

BTW it's not FAE, it's "under water exhaust" :biggrin:

still want pics ;) ... unless... new company about.. called UWE coming out :whistle:

Share this post


Link to post
formulaben

My answer is yes too...but I doubt it is substantial.  All I know is the CO mitigation is of course important but I really like how quiet the boat is.

Share this post


Link to post
Ndawg12

I'll get pics up when I can.  I'd imagine the loss in speed was due to drag.  I can't see a 3" port choking anything. BICBW

Share this post


Link to post
That Guy

Wanna build me one too? LOL

I had a FAE on my last boat and am looking into ordering it on my new boat, love how quiet it makes the boat and cleaner is safer!

Share this post


Link to post
kerpluxal

Well... IMHO.. FAE uses the scare tactic of CO entering boat... I know it is plausible and has happened.. but I have been in boats for 40 years and have not had an issue yet... 

Now.. I am looking for stereo enhancement behind the boat (a quieter boat in cabin and behind boat)... but not lose my slalom speed nor wake (friend put one on his MB and it honestly changed things up to the point he just took it off and never got another one for any of his boats.)

Edited by kerpluxal

Share this post


Link to post
BlindSquirrel

sub'ed for the photos, sounds cool.

Share this post


Link to post
Woodski

@Ndawg12:  fabbing up stainless projects is always fun.  A couple of things to consider on the exhaust system and backflow, first the amount that will enter the system when you cut the throttle and the boat settles to rest and probably more important is the amount of water that would enter the system while operating in reverse (with little throttle application and thus little exhaust volume to counter the incoming water).  The flappers do their job in these conditions or really stopping water coming up from the opposite direction of forward travel.  If your configuration does not really have a rearward facing opening you have a lot less to worry / think about.   The silent rider would offer the extra volume as protection but not a lot of an obstacle as the water is already in the system and it is not like closing a door to stop something coming in which is pretty much what the flappers do.

To see if it is water drag (most probable) or perhaps exhaust restriction, simply calculate the area of the riser exits v the exhaust exit to see if you lose or gain effective area.  You do need additional area past the riser as water gets mixed in taking up some of the available volume.  You can also calculate losses due to bends, there are tables that identify % flow loss or restriction based on # of bends and angles.

Share this post


Link to post
MadMan

At one time I considered fabing one of these up that had flexible joints and was supported by the wedge.  If the wedge was up, it would pick the exhaust up out of the water. wedge down-exhaust down.  This was because I wanted to hear the engine sound at cruise.

Also, I'm an empirical kind of guy, it I wanted to see if the mph loss was because of drag (instead of exhaust restriction), I'd construct a test that had the same size pipe in the water (just attached to the swim platform) but the exhaust came out the factory exits.

Share this post


Link to post
Steve B.

Now that I think about it, idling around the stereo should be heard better too.

Steve B.

Share this post


Link to post
Ndawg12

We should be done today or tomorrrow.

 

sfgasfagsfg_zpsuazjx6s4.jpg

Share this post


Link to post
Falko

Has any inboard sport boat done exhaust out the bottom of the boat? There are some inboard pleasure boats that do this. 

Share this post


Link to post
shawndoggy
2 minutes ago, Falko said:

Has any inboard sport boat done exhaust out the bottom of the boat? There are some inboard pleasure boats that do this. 

the new sea ray does

Share this post


Link to post
Falko

They have pipes that go down into the water. The ones I've seen terminate just through a hole in the bottom of the boat, usually to the side of the prop to not cause cavitation. Not sure it would help with fumes as the exhaust could run along the bottom of the boat and then be released, but for noise purposes it should help considerably.

Share this post


Link to post
Cole2001

what are you guys making the diameter of the pipe? What I found from FAE the standard was 3in

Share this post


Link to post
Ndawg12

Yes, mine is 3" .065 wall stainless.  

asdfasdf_zpsz0t2xbh5.jpg

Share this post


Link to post
shawndoggy

you are gonna support it with more than just screws through the transom tho right?

Share this post


Link to post
Ndawg12
46 minutes ago, shawndoggy said:

you are gonna support it with more than just screws through the transom tho right?

Yes, you can barely see it but there's a hefty piece of 1" square bar running across the top of the wedge mount.

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...