Reply
 
Thread Tools Display Modes
 
Old 04-21-2016, 10:12 AM   #1
Guru
 
City: Seaford Va on Poquoson River, VA
Country: United States
Vessel Name: Old Glory
Vessel Model: 1970 Egg Harbor 37 extended salon model
Join Date: Jan 2016
Posts: 1,306
Underwater exhaust exit.

Instead of above water exhaust, why not exhaust completely underwater?
Advantages are less soot, less fumes, less engine exhaust smells, less CO, less air pollution for you to breathe in.
I was thinking a contoured or angled pipe type through hull, as long as you can not reverse siphon, so might have to have a small exhaust air hole above the water?
__________________
Advertisement

sdowney717 is offline   Reply With Quote
Old 04-21-2016, 10:32 AM   #2
Senior Member
 
Old deckhand's Avatar
 
City: Sitka
Country: Same
Vessel Model: Transpacific Marine Eagle 32
Join Date: Dec 2014
Posts: 497
Sudbury did make an exhaust muffler that a person could place over the existing transom exhaust which would direct the exhaust down into the water. The muffler had several small relief holes above the water line in order to not direct the entire exhaust under water. I place one on a boat and it did work well.
__________________

Old deckhand is offline   Reply With Quote
Old 04-21-2016, 10:41 AM   #3
Senior Member
 
capt jerry's Avatar
 
Join Date: Oct 2007
Posts: 321
i run a 58 hatteres with 16 92s DD that has a under water EX but it also has small ones above water to lessen pres.when running slow,never a problem
capt jerry is online now   Reply With Quote
Old 04-21-2016, 11:26 AM   #4
Guru
 
refugio's Avatar
 
City: Meydenbauer Bay Yacht Club
Country: USA
Vessel Name: Refugio
Join Date: Mar 2012
Posts: 1,141
Quote:
Originally Posted by Old deckhand View Post
Sudbury did make an exhaust muffler that a person could place over the existing transom exhaust which would direct the exhaust down into the water. The muffler had several small relief holes above the water line in order to not direct the entire exhaust under water. I place one on a boat and it did work well.
Salisbury Hydro-Vac. I installed one a number of years back - it bolted right over the exhaust port flange. It made the aft deck somewhat more pleasant underway, but the exhaust gas still bubbles up and drafts back towards the boat. Since I already had a large Aqualift muffler it did almost nothing for sound underway - and burbling rather than splashing at idle.


Keith
__________________
Keith
refugio is offline   Reply With Quote
Old 04-21-2016, 12:07 PM   #5
Senior Member
 
Keysdisease's Avatar
 
City: South Florida
Country: USA
Join Date: Sep 2014
Posts: 461
Underwater exhaust is common on larger boats and yachts. There is always a slow speed bypass as described in previous posts because without the bypass relief backpressure would become excessive and could damage engine.

Outboard motors with thru-hub exhaust have bypasses too on the back of the leg below the cowling as an example.

I have seen on smaller boats (approx. 40 ft) an exhaust pipe extending just below the hull bottom and turning aft 90* as in pic 1 and 3 below

What this does and what larger boats do with a cowl (pic 2) is create low pressure at speed that sucks exhaust gasses out the bottom. This creates kind of an automatic switch from the low speed bypass to the underwater exhaust path as the vessel increases speed as exhaust gasses will travel the path of least resistance.

Attached Images
   
Keysdisease is offline   Reply With Quote
Old 04-21-2016, 12:32 PM   #6
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,924
Lots of boats with them...early 2000's Sea Rays had them..

Can't say they were terrific.
psneeld is offline   Reply With Quote
Old 04-21-2016, 12:46 PM   #7
Senior Member
 
Keysdisease's Avatar
 
City: South Florida
Country: USA
Join Date: Sep 2014
Posts: 461
Very common on Sea Rays from about the Sundancer 34 and up. Sea Ray actually has a patent on what they use:

Patent US5700172 - Submerged marine exhaust system - Google Patents



Quote:
Originally Posted by psneeld View Post
Lots of boats with them...early 2000's Sea Rays had them..
Can't say they were terrific.
Keysdisease is offline   Reply With Quote
Old 04-21-2016, 01:24 PM   #8
Guru
 
Brooksie's Avatar
 
City: Cape Cod, MA
Country: USA
Vessel Name: Island Seeker
Vessel Model: Willard 36 Sedan
Join Date: Oct 2007
Posts: 954
I have a Salisbury HydroVac muffler on my lobsterboat. Its been installed for 30 seasons now and I would not be without it. My exhaust was originally offset on the transom but I moved it to the center. Now it is inline with the propeller race and works even better.
My HydroVac is made of heavy neoprene, streamlined, and fits right over the exhaust flange. It came with neoprene shims so it could be aligned with the flow when offset on a curved transom. It does have a small relief hole so that water is not drawn in as the exhaust cools after shutdown.
I am sure I have run over things over the years but the neoprene is flexible enough that it has never been knocked off.
Brooksie is offline   Reply With Quote
Old 04-21-2016, 08:29 PM   #9
GFC
Guru
 
GFC's Avatar
 
City: Tri Cities, WA
Country: USA
Vessel Name: Beachcomber
Vessel Model: Sea Ray 550 Sedan Bridge
Join Date: Nov 2012
Posts: 2,705
I don't know if this is what you're looking for, but when we bought our boat I had an "exhaust water separator" installed on the gen exhaust. It takes the water component out of the exhaust and sends it down below the boat via a thru hull. What comes out the back of the boat (above the water) has the sound of just a quiet hum. If you're standing on the dock next to it you don't even notice it is running unless you look down and see the ripples on the water.
__________________
Mike and Tina
Beachcomber 1995 Sea Ray 550 Sedan Bridge
GFC is offline   Reply With Quote
Old 04-21-2016, 08:39 PM   #10
Senior Member
 
101TUG's Avatar
 
City: Gustavia
Country: St Barth
Vessel Name: Super MAN
Vessel Model: Terranova Explorer
Join Date: Apr 2016
Posts: 321
Quote:
Originally Posted by sdowney717 View Post
Instead of above water exhaust, why not exhaust completely underwater?
Advantages are less soot, less fumes, less engine exhaust smells, less CO, less air pollution for you to breathe in.
I was thinking a contoured or angled pipe type through hull, as long as you can not reverse siphon, so might have to have a small exhaust air hole above the water?
the problem is back-pressure on exhaust system kill you engine if you underway with specific exhaust underwater that ok but at low speed or no speed you need system with by-pass to go up of waterline.
problem is also noise and spray for exhaust air coming at the surface.

Hugues
101TUG is offline   Reply With Quote
Old 04-21-2016, 11:28 PM   #11
Guru
 
refugio's Avatar
 
City: Meydenbauer Bay Yacht Club
Country: USA
Vessel Name: Refugio
Join Date: Mar 2012
Posts: 1,141
Quote:
Originally Posted by Brooksie View Post
I have a Salisbury HydroVac muffler on my lobsterboat. Its been installed for 30 seasons now and I would not be without it. My exhaust was originally offset on the transom but I moved it to the center. Now it is inline with the propeller race and works even better.
You had the HydroVac in both settings? My exhaust is also offset and I would consider moving it. What percentage "better" after moving?


Keith
__________________
Keith
refugio is offline   Reply With Quote
Old 04-22-2016, 07:15 AM   #12
Guru
 
City: Seaford Va on Poquoson River, VA
Country: United States
Vessel Name: Old Glory
Vessel Model: 1970 Egg Harbor 37 extended salon model
Join Date: Jan 2016
Posts: 1,306
I actually have 2 of these underwater devices, similar to Salisbury HydroVac.
I dont know who manufactured these, but did find their patent number US3162171A.
these came off an 1966 wooden cruiser that was being crushed at the marina.
http://www.freepatentsonline.com/3162171.pdf
https://patents.google.com/patent/US3162171A/en

I traced them by their embossed patent number. They are heavy hard rubber.
My transom has a curve, and these came with a piece to allow for the curve.


Do these devices cause an exhaust restriction?
Reading the patent info, they do not.
I painted mine but they are not on the boat.
These wont snag, the bottom is inline with the hull.
Actually I am trying to convince myself to put them on the boat.









photo sharing websites
sdowney717 is offline   Reply With Quote
Old 04-23-2016, 09:29 PM   #13
Guru
 
Pgitug's Avatar
 
City: Punta Gorda, fl
Country: Usa
Vessel Name: Escapade
Vessel Model: Nordic Tug 37 2002
Join Date: Jan 2015
Posts: 989
Nordic Tugs have under water exhaust systems with a three inch above water bypass.
Pgitug is offline   Reply With Quote
Old 04-23-2016, 11:03 PM   #14
Senior Member
 
IRENE's Avatar
 
City: Port Angeles, WA
Country: USA
Vessel Name: Irene
Vessel Model: Skagit Orca 27XLC
Join Date: Jan 2016
Posts: 316
We have a Volvo Penta D4-260 attached to a DPH drive. The exhaust is completely underwater at displacement speeds. It is at the cavitation plate level, so basically at water level when on plane.

We have had no issues with this system. It bubbles quite a bit while idling in neutral - there is a lot of air going through that engine. The engine is electronically controlled, so theres little/no smoke produced and I have never seen any.
IRENE is online now   Reply With Quote
Old 04-24-2016, 11:23 AM   #15
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,890
I've been on lots of boats with underwater exhaust. They can work, but not a big fan. Unless designed right, backpressure can be pretty high or even over spec. I prefer a good muffler and tailpipe above waterline. Nice to be able to see, at a quick glance, that you have good water flow and a clean burn.

The IPS really needs a relief line. Constantly blowing bubbles under the boat is annoying.
Ski in NC is offline   Reply With Quote
Old 04-24-2016, 12:37 PM   #16
Guru
 
City: Seaford Va on Poquoson River, VA
Country: United States
Vessel Name: Old Glory
Vessel Model: 1970 Egg Harbor 37 extended salon model
Join Date: Jan 2016
Posts: 1,306
Quote:
Originally Posted by Ski in NC View Post
I've been on lots of boats with underwater exhaust. They can work, but not a big fan. Unless designed right, backpressure can be pretty high or even over spec. I prefer a good muffler and tailpipe above waterline. Nice to be able to see, at a quick glance, that you have good water flow and a clean burn.

The IPS really needs a relief line. Constantly blowing bubbles under the boat is annoying.
Run a tell tale, a 1/4 inch polyethylene (ice maker) plastic tubing shunting some water flow from the end where it dumps before the mixer out the hull near the exhaust outlet, that way when you see water coming out the little tube, you know the raw water pump is pumping.


These ones I have, a hole exists above the waterline in them. Hole is about 1/2 inch. I think it modifies the idling sound, less gurgling.

I think if your burn is really bad, you would still notice even with underwater exhaust.
To me the entire purpose is reduce the air pollution you will be breathing from exhaust fumes. I know some boats suck exhaust fumes back into the boat. Or wind blows back into the boat exhaust fumes.
__________________

sdowney717 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 08:31 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012