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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel > exhaust woes
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Topic Review (Newest First)
08-05-2009 07:36 PM
OldColumbia Dear Jhack,

You're absolutely right, it's "raw" water from the heat exchanger cicuit. I comes from the pump driven by the V belt supplied by the seacock typically by a 3/4' or 1" hose that enters the exhaust on the " down" side of either your homemade or manufactured exhaust riser or elbow.

Some water lock mufflers are metal, some are plastic some have drains to winterize or drain the exhaust system but most are about the same size for small diesel auxiallary engines less than 40HP. the key issue is whether the remaining water in the exhaust can be drained away from the engine when it isn't running.
You can buy manufactured exhaust elbows and risers from Original Equipment manufacturers or aftermarket manufacturers since almost every inboard powered boat needs one except for "drystack" exhausts used on fishing boats and trawlers.
It really depends on whether your engine is above or below the waterline to determine if you need a riser or not. Westerbeke has great Adobe manuals on line foor the 25XP to locate parts numbers. The elbows for the 3 cylinder M30 might work as well.
08-05-2009 07:00 PM
DwayneSpeer
exhaust

Quote:
Originally Posted by jhack82 View Post
oldcolumbia, thank you for all the help, this does't make sense then, or I am not understanding how this works. I had accidentally left my bilge pump off when the exhaust piece finally decided to break off, so the bottom of my boat was covered in warm water that had escaped out of the exhaust. i did not taste it, and it was black too, but there was so much of it, it had to be seawater, and I just traced the hose to the saltwater intake as well. looking at my manual, I see it is a freshwater system, but I am pretty sure its seawater from the heat exchanger that is flowing into the exhaust, and overboard from the water lift muffler, not the engine coolant. also, this prompted me to look more thoroughly at the waterlift muffler, it has no water outlet, is this right? does the exhaust and the water all exit through the exhaust hose? I am thoroughly confused now. where do you get the manufactured elbow? again thanks

regards,
jhack82
s/v Firefly
Yes, it's salt water. All engines inject water into the exhaust system just after it exits the engine to cool the exhaust. The waterlift muffler just adds a place where the water collects temporarily to provide a muffling effect so that your exhaust isn't too loud. That water is then blown out of the boat exhaust along with all the exhaust gasses.

One of the things you need to get into the habit of doing is checking the exhaust a few seconds after you start the engine to assure that water is in fact coming out of the exhaust. That assures you that the cooling system is working before you harm something by running too long without it.
08-05-2009 06:36 PM
jhack82 oldcolumbia, thank you for all the help, this does't make sense then, or I am not understanding how this works. I had accidentally left my bilge pump off when the exhaust piece finally decided to break off, so the bottom of my boat was covered in warm water that had escaped out of the exhaust. i did not taste it, and it was black too, but there was so much of it, it had to be seawater, and I just traced the hose to the saltwater intake as well. looking at my manual, I see it is a freshwater system, but I am pretty sure its seawater from the heat exchanger that is flowing into the exhaust, and overboard from the water lift muffler, not the engine coolant. also, this prompted me to look more thoroughly at the waterlift muffler, it has no water outlet, is this right? does the exhaust and the water all exit through the exhaust hose? I am thoroughly confused now. where do you get the manufactured elbow? again thanks

regards,
jhack82
s/v Firefly
08-05-2009 01:51 PM
OldColumbia Dear Jhack,

I apologize, since I misread that you had an Atomic 4. I replaced my last Atomic 4 with a remanufactured Universal 25XP (because I could, based on the footprint) and the riser elbow/anti-syphon system that had been installed after A4 rebulid number two (except for the galvanized nipple between the manifold and riser/elbow) works fine.
Since the 25XP is freshwater cooled you shouldn't have the corrosion inherent with salt water and heat that ate my former wrapped "homemade" riser. The manufactured elbow cost about $130 and I bought brass fittings threaded to hose bib for the connection to the exhaust hose to the Vetus water pot muffler/back flow preventer. Likewise, brass fittings were used for the water injection port.
Since the water injection portion of the elbow is molded above and around the hot gas section, the only "hot" section is the nipple between the manifold and the elbow approximately 2" between threaded ends.
Because my engine is just at or below the water line, anti siphon breaks are important to keep from "sucking water" into the block by excessive cranking that can fill the pot muffler. It's better to close the seacock and reopen when the engine starts than ruin an engine that tries to compress water.
Hope this helps.
08-05-2009 12:22 PM
jhack82 OldColumbia, I have a univesal 25XP, do you still recommend an A4 elbow? I was planning on replacing the setup I described earlier once every three years, at roughly $50 a pop, it's a minimal cost and from what I gather that is about the expected life cycle of any setup(4-5 years). also, the same thing happend to me, the nipple that caried the dexhaust/raw water to the pipe corroded away and that is where my leak started. I do not quite understand how having the cooling come from atop means yuou don't have a heat wrap, do you mean only on the seawater side? thanks for the help, i apprecaite it.

regards,
Jhack82
S/v Firefly
08-04-2009 05:44 PM
OldColumbia Dear Jhack,

I would recommend getting a manufactured exhaust elbow for the A4. After 3 rebuilds of A4's I went diesel but the original exhaust (dry jacket) weighed too much and corroded, the hand built galvanized elbow wrapped in heatshield disintegrated within the wrap from raw salt water cooling, and after replacing that with the manufactured elbow and anti siphon set up the galvanized joint between the manifold and elbow fractured after being attached to the diesel.
If you're running raw water the best setup will probably last 5 years if you don't asphyxiate yourself with CO before it rusts through.
The advantage of the precast elbows is that the cooling water come in over the top of the elbow so it is cool on top ( where it usually is below the underside of the cockpit sole) and obviates the need for the heat wrap that can hide a leak.
Thank goodness when the galvanized section fractured I was towed to a yard that honestly assessed the problem as a $5.00 pipe joint that could be removed from the manifold with a pipe wrench and didn't require a new manifold end.I suggest a fresh water system and the less metal in the exhaust the better.
08-03-2009 11:04 PM
jhack82 Hello, thank you for all the advice. I noticed something else when i was working on it yesterday, the exhaust riser has a copper tube that comes down from the inlet nipple from the water inlet. Is that standard? Also, I have been looking around and is there a problem with building a new system myself? I found a reducing Tee at plumbing fittings direct that would replace the old elbow. Is this a bad idea? Looking at it, it doesnít seem to be any different, the exhaust still comes in from the top, and I could get a spare to have handy when it corrodes again. This does raise one issue, what should the fittings be made of? Will galvanized pipe be enough, or should I go with stainless or brass? I have read stainless is bad, but is commonly used as long s welds can be avoided, or done properly. I have only heard of a guy redoing his A4 system using brass, and some people just say to use the black pipe and replace it every 4-5 years. I only plan on using the motor sparingly, I have a sailboat, not a motorboat and I like my quiet. Any advice would be appreciated.


Regards,
Jhack82
S/V firefly
08-01-2009 09:46 PM
BarryL Hello,

I went through this last month. The mechanic at my boat yard replaced the exhaust system from the exhaust manifold to the hose that leads to the waterlift muffler. The price was $350.

Barry
08-01-2009 06:49 PM
trantor12020 where the cooling water connects to the exhaust is the mixing elbow. you're better off getting a new mixing elbow. beside corrosion & leak of the joint, its likely you have fouling and particle blockage of the elbow, leading to the muffler. with new assembly your engine will breathe better.
08-01-2009 04:44 PM
fordo I believe that the corroded fitting is where the raw cooling water is injected into the exhaust, cooling it and providing water for the waterlift muffler (the "black round thing"). The black should just be the exhaust and the water is the raw water from the heat exchanger (if you have one) or the engine block (if you are raw water cooled). The elbow that the fitting goes into is usually cast metal and difficult, though not impossible, to tap with new threads. look to see if the threads in the elbow are ok, if they are you just need a new fitting. If the're corroded you could try to drill out the corrosion and retap; or spring for a new elbow.

There should not be any oil there at all. Diesel exhaust is pretty dirty stuff, good luck cleaning it up!
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