Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-16-2020, 05:41 PM   #1
Veteran Member
 
City: Grand Rapids, MI
Vessel Model: 1973 Concorde 41 DC
Join Date: Sep 2020
Posts: 81
Exhaust water bypass hose

I'm replacing the engine water hoses on the new-to-me boat with twin Perkins 6.354MGT's. In the hose from the heat exchanger to the mixing elbow on each there's a tee with another hose going to a separate through hull with an above waterline closed seacock. It seems if the seacock were opened the raw water would bypass the muffler and exhaust pipes and discharge directly overboard. I've never seen this before and can't imagine why one would to do that. Anyone know what this is for and can I safely eliminate it? Thanks.
__________________
Advertisement

jgwinks is offline   Reply With Quote
Old 11-16-2020, 07:12 PM   #2
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,985
Common way to do wet exhaust. Often done when exhaust backpressure is high due to too much water in the muffler. So some is diverted overboard. Only about 25% of engine cooling water is needed to cool the exhaust.

Might also reduce the whoosh-whoosh sound of water being expelled from the tailpipes.

But you have to actually throttle that bypass valve. If left full open, exhaust may get too hot and that is a problem you do not want to have. Some previous owner might have said "screw it" with regards to modulating that flow. Just closed it and was done with it.

If running engines at light load, back pressure is a non-issue.
__________________

Ski in NC is offline   Reply With Quote
Old 11-16-2020, 09:43 PM   #3
Veteran Member
 
City: Grand Rapids, MI
Vessel Model: 1973 Concorde 41 DC
Join Date: Sep 2020
Posts: 81
Ok thanks. This is the first larger boat I've owned. None of my commercial boats have this setup and I don't think it's ever done on the smaller engines in sailboats. The seacocks appear to be fully closed, and we didn't see water coming out of those outlets on the sea trial. I think I'll keep the setup as is. The engines are the high hp version and the boat will plane at about 18 know, but I don't intend to run out anywhere near that fast. I'll just leave them closed.
jgwinks is offline   Reply With Quote
Old 11-16-2020, 09:48 PM   #4
Guru
 
BruceK's Avatar
 
Join Date: Oct 2011
Posts: 11,724
This thread might be of interest: https://www.trawlerforum.com/forums/...ust-34924.html
__________________
BruceK
2005 Integrity 386 "Sojourn"
Sydney Australia
BruceK is offline   Reply With Quote
Old 11-17-2020, 05:51 AM   #5
Guru
 
Keysdisease's Avatar
 
City: South Florida
Join Date: Sep 2014
Posts: 835
Excellent, someone that actually understands exhaust bypass. Human nature leads many an yacht engineer or boat owner to come aboard or purchase a new to them boat, see a valve that is neither fully open or closed, and feel it necessary to "fix" it by either fully opening or closing.

On some boats to eliminate that compulsion after "dialing in" the valve setting using a back pressure gauge the valve handle is removed.





Quote:
Originally Posted by Ski in NC View Post
Common way to do wet exhaust. Often done when exhaust backpressure is high due to too much water in the muffler. So some is diverted overboard. Only about 25% of engine cooling water is needed to cool the exhaust.

Might also reduce the whoosh-whoosh sound of water being expelled from the tailpipes.

But you have to actually throttle that bypass valve. If left full open, exhaust may get too hot and that is a problem you do not want to have. Some previous owner might have said "screw it" with regards to modulating that flow. Just closed it and was done with it.

If running engines at light load, back pressure is a non-issue.
Keysdisease is offline   Reply With Quote
Old 11-26-2020, 05:19 PM   #6
Guru
 
kapnd's Avatar
 
City: hawaii
Vessel Name: #31
Vessel Model: ex-Navy MUB 50 fish/cruise
Join Date: Aug 2013
Posts: 659
Perkins raw water systems don’t move an excessive amount of water, so I wouldn’t think you’d need to bypass any water unless there’s some serious restriction issues in the exhaust.
Perkins Cast iron exhaust elbows (and exhaust manifolds) are a known sore spot, prone to corrosion and plugging up the spray holes with rust, so make sure that this isn’t the reason for the bypass!
__________________
You can lead a horse to water,
But you can't make him ski...
kapnd is offline   Reply With Quote
Old 11-26-2020, 07:13 PM   #7
Veteran Member
 
City: Grand Rapids, MI
Vessel Model: 1973 Concorde 41 DC
Join Date: Sep 2020
Posts: 81
Thanks. I'm planning to take all that apart anyway. Only 600 hours on the 1973 engines, so I'm more concerned with things being clogged up rather than worn out.
__________________

jgwinks is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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



» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 06:35 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×