Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 20-08-2013, 19:03   #1
Registered User

Join Date: Nov 2009
Posts: 5
Water Jacket or Hot Exhaust?

Need advice on my current exhaust configuration. I have an universal m4-30 located in the bilge. A custom fabricated water jacketed exhaust pipe leaves the manifold and runs 2.5 feet in the bilge and 3 feet vertically behind the aft bulkhead. Raw water then leaves the jacket entering the top of the exhaust riser falls to the muffler and exits the boat. The water jacketed section has failed, leaking raw water in the manifold. No major damage this time but I hate this system. Question? Is 5.5 feet of wrapped hot exhaust to long/ to hot? Am I stuck rebuilding the current pipe? Thanks for any advice.



Click image for larger version

Name:	image-4201544699.jpg
Views:	160
Size:	392.8 KB
ID:	65795
__________________

__________________
ffjme is offline   Reply With Quote
Old 20-08-2013, 20:57   #2
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 1,373
Images: 7
Re: Water jacket or hot exhaust?

Both my engines have had exhaust water locks connected to the exhaust/water mixer directly behind the engine with about 5m of hose rising to just under the deck and then through the transom and I have never had a problem with water back into the engine. I have an anti siphon loop with rubber air bleed in valve between the raw water outlet on the water cooled manifold and the exhaust/water mixer.
__________________

__________________
RaymondR is offline   Reply With Quote
Old 21-08-2013, 06:12   #3
Registered User

Join Date: Dec 2008
Location: Oriental, NC
Boat: Mainship Pilot 34
Posts: 1,429
Re: Water jacket or hot exhaust?

5-6' of wrapped hot exhaust pipe is certainly unusual. But if you ventilate that compartment well and keep the pipe away from adjacent structures, you should be OK. Replacing that jacketed pipe in kind will be expensive, but better.
__________________
djmarchand is offline   Reply With Quote
Old 21-08-2013, 15:28   #4
Registered User

Join Date: Apr 2007
Location: Australia
Boat: Island Packet 40
Posts: 1,373
Images: 7
Re: Water jacket or hot exhaust?

If you have room to install a mixer immediately following the exhaust manifold and a waterfall device immediately after the mixer you should not require the water jacketed intermediate pipe or lagging as the cool raw water cools the exhaust gasses when they mix in the mixer. Can you provide an overhead image of the back end of your engine?
__________________
RaymondR is offline   Reply With Quote
Old 22-08-2013, 08:23   #5
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Water jacket or hot exhaust?

We had the exact engine and exact mounting location and exact runs in our previous boat. While not ideal from a maintenance standpoint, it was never a problem.

I replaced it once in 15 years. The beauty of that engine is the exhaust flange is a simple female NPT fitting. So you can make your own exhaust riser and injector out of common inexpensive pipe and fittings. Black pipe is best. Galvanized pipe will release fumes - so run it hot with a lot of ventilation for the first few hours until they stop.

McMaster-Carr sells the fiberglass heat wrap for the standing part very cheaply (just bought some for a similar project).

Mark
__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 22-08-2013, 09:37   #6
Registered User

Join Date: Nov 2009
Posts: 5
Mark how hot would that pipe get? Thanks
__________________
ffjme is offline   Reply With Quote
Old 22-08-2013, 10:05   #7
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,347
Re: Water jacket or hot exhaust?

The other thing to consider is you should install a bellows or two to avoid vibration cracking on that dry exhaust link. i would definitely stay wet. Water jackets go bad occassionally, just get 'er replaced.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 22-08-2013, 10:10   #8
Registered User
 
rw58ph's Avatar

Join Date: Jun 2013
Location: Seattle WA
Boat: Roughwater, pilot house, 58 ft
Posts: 485
Re: Water jacket or hot exhaust?

What you might want to move the whole exhaust closer/next to the engine which would eliminate the 2 ft horizontal jacket, so would be only the 3 ft vertical. Where is the boats water line so the raw water injection might be lower? So you might be able to shorten the total length of the hot exhaust. Would still have to have to heat wrap or water jacket the exhaust but no as much.
__________________
rw58ph is offline   Reply With Quote
Old 22-08-2013, 10:44   #9
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Water Jacket or Hot Exhaust?

The pipe before the water injection will get hot enough to burn things.

If your installation is like mine, you don't have many choices because the engine is mounted to close to a bulkhead to shorten the horizontal run and too low to shorten the vertical rise. And there is not enough room beneath it to make a close water injection with anti-syphon loop.

Mark
__________________

__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Reply

Tags
water, exhaust

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fresh Water Tank Cleaning Dougfuller Plumbing Systems and Fixtures 76 23-07-2014 09:00
Laundry and Hot Water Showers sailor49 Meets & Greets 31 25-05-2013 07:06
Replaced Water Heater, Only Seems To Work From Shore Power Not Engine bstowers Plumbing Systems and Fixtures 7 25-04-2013 13:21
Exhaust Refit wgh52 Construction, Maintenance & Refit 7 01-03-2013 13:31
If You Don't Drink the Water? thompsonisland Provisioning: Food & Drink 174 09-11-2012 17:18



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:31.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.