Wet Exhaust Question

[oakman]

So we have to do this without a picture for the moment. The basic question is can the muffler be installed above to outlet from the exhaust riser?

The situation is this: Universal Diesel model 5411, a little two cylinder job. I had to replace the heat riser where the cooling water is added to the exhaust gases. The only model available is different enough that I can no longer fit the muffler, Vetus waterlock LP 40, where it was. I can get it level with the waterline but the inlet is above the heat riser outlet. I can get a loop in the exhaust hose such that it will be the lowest point in the system so water will not sit in the riser.

Opinions please, thanks.
Oakman

[Ed Burnett]

Assuming this is an installation in a sailing boat, with the engine near or below the waterline, the rule of thumb is that the water trap should be 300mm (12") below the high point of the injection elbow. One of the things the water trap does is provide a low point for water in the exhaust system to drain down to when the engine is stopped. As a rough guide, you can consider there to be about 20% of the internal volume of the hose sloshing about at any one time, and this should no more than one third fill the water trap.

In practice, it can be tricky to get the trap low enough, particularly in small sailing boats where the engine tends to be pushed as far aft as possible. Sometimes you can get the trap down under the shaft, otherwise I have in the past put it in front of the engine to get it low enough. I have seen installations where the hose coils around under the engine to provide sufficient volume low down, but this never strikes me as a nice solution.

There is some good general guidance on exhausts here: http://www.halyard.eu.com/Knowledge/low_mounted_engines.html

[oakman]

Ed

Thanks for the reply. Yes, it is a small sailboat. Crocker Stonehorse in wood built by the Apprenticeshop back when she was in Bath.

The previous installation was a little lower than the injection elbow, but not 12" by any means and it was canted to the side. I may have to go loop route as there is no room in front of the engine for muffler. I will check out the link.

Thanks again
Oakman

[wizbang 13]

This is something I cannot follow WO pics and diagram.
But it sounds crazy to put a waterlock muffler above exhaust riser. The muffler is filling with water while the engine is cranking over ( untill it starts)
Why do you need a riser, a high point in the exhaust hose after the muffler is all I have ever done?

[Ed Burnett]

In an ideal world the exhaust would drop down from the engine to the water trap, then straight up to a high point under the deck somewhere, and finally down to the outlet. The problems start when you can't get the water trap low enough, so you need a high rise elbow to gain a bit of height (prior to injecting the cooling water) and thus be able to drop a sensible distance down to the water trap.

It is indeed not that good to have the water trap higher than the engine. As you say, the engine will be pumping water through into the exhaust if you have to crank it for a while to start it, and there is already the water in there from the last time the engine was run. The water trap's purpose is to be a high volume collection point for water at the lowest point of the system, and to keep this water safely contained sufficiently low down to prevent it getting back into the engine whatever the boat might do.

Exhaust systems can be surprisingly tricky to make reliable, and we haven't even got on to siphon breaks yet.....

[oakman]

Well, I spoke to the Vetus man today and sure enough, muffler is to be lowest point in the system, just as Ed has suggested. There are a couple other models that may work with our configuration, BUT!

"so you need a high rise elbow"

Sparked and idea. I have room above the engine, two 90 degree elbows and a nipple and I can raise the injection elbow enough to get the job done. There is a siphon break between the engine and the injection elbow, old fashioned, but it gets the job done. Might not be as pretty as the elbow right at the exhaust manifold, but I take function over form most days. Any issues with adding a few inches of vertical run on the dry side of the exhaust?

Oakman

[kulas44]

Make the riser as high as possible. Dry and lagged heavily. Injection point as low on riser as possible aft of highest point. Simple stuff, usually overlooked or ignored.

[wizbang 13]

I just recently looked at a little diesel to troubleshoot steam coming out the exhaust. Chap thought he might have a gasket leak. It was caused by the riser loop getting very hot, cuz it was dry, heavy iron pipe.Plus it was wrapped with dry tape. By the time the x gasses reached the water injection they (the gasses) were hotter, and steamed up the injected raw water.

(I recommended he begin by removing the tape, then building the riser of lighter weight metal to let heat off the dry exhaust part)

[oakman]

"lagged heavily" What does this mean please?

O

[Breakaway]

Lagging means insulation.

[ramillett]

If you can keep your riser simple , I would recommend that you water cool it . I had a dry stack for years , and burned a lot of stuff like me :)
Even though my riser comes to the deck , I need to use a valve on windy days to keep the water out of the engine .
After jacketing , I did not need a muffler anymore .

http://i697.photobucket.com/albums/vv332/ramillett/millett/IMG_8799.jpg

[Ed Burnett]

Sparked and idea. I have room above the engine, two 90 degree elbows and a nipple and I can raise the injection elbow enough to get the job done. There is a siphon break between the engine and the injection elbow, old fashioned, but it gets the job done. Might not be as pretty as the elbow right at the exhaust manifold, but I take function over form most days. Any issues with adding a few inches of vertical run on the dry side of the exhaust?

Oakman

Well if you have space that is a nice way to solve the problem. The issues surrounding the dry bit of the exhaust are mainly about heat (ie. not setting fire to things) and vibration. A good bit of lagging deals with the heat. The thing to watch for vibration wise is the potential for failure of a long and unsupported section of rigid piping hanging off the back of the engine - in your case it doesn't sound like it will be large enough to be problematic, but were it to be longer you might want to consider a dry exhaust bellows of some kind and support brackets for the far end of the riser.

Siphon break nice and high I trust, and accessible for checking and cleaning every now and again. One of the more critical components in a seaworthy exhaust system and frequently under-appreciated!

[oakman]

Again, thanks for the replies.

There would not be much pipe to speak of. There is a close nipple on the exhaust manifold, I would add a 90 degree elbow, approx 3" nipple and another 90 degree elbow, then the injection elbow, or heat riser.

OK, another question, "dry exhaust bellows" going to google now.

I will definitely pay attention to heat and support. Not sure when I will be able to get down and put this together but I will post the outcome if this solution works.

Oakman

[wizbang 13]

I do not put a siphon break in the x haust. Mine goes in the raw water import, after the impeller.

[kulas44]

No need for a bellows on your setup, but do try to make the riser as tall as space allows. Also if the entire riser is water cooled saltwater will stand in the jacket close to the engine where it can't get out do to being "uphill", eventually it will corrode thru allowing water into the engine, not good. A better aproach is to build in the injection point on the "downhill" side so even if it does corrode thru it can't ruin your engine. A waterlift muffler of the largest possible size will allow for a lot of engine cranking time, you can easily build this yourself. I disagree with using a lighter and uninsulated exhaust to reduce steam. The dry riser is not the problem as the exhaust gas is not going to get hotter because of it, it's as hot as it will ever be when it leaves the engine. I suggest reading Gerr's book on boat mechanical systems, he covers all of this (and much more) in great detail.

[oakman]

The entire riser is not water cooled, it is a factory part and about 10" long. The cooling water enters at the top of the fitting but travels to the bottom in its own channel and is mixed with the gasses about 1/2" from the end of the fitting or about 9 1/2" below the highest point in the system. I will look up Gerr's book, have been using Nigel Calder's book for reference so far.

Oakman

[Ed Burnett]

I do not put a siphon break in the x haust. Mine goes in the raw water import, after the impeller.

Quite right - the siphon break is in the cooling system, not the exhaust.

One thing to bear in mind is that if you put it before the heat exhanger, in some installations this will lead to the heat exchanger draining down into the exhuast water trap when the engine is stopped. I don't know if this is preferable for the heat exchanger or not, but it may have a bearing on the size of water trap that you need.

[Todd D]

My exhaust riser is made from black iron pipe. The riser is 12" high and has an elbow at the bottom that connects to the adapter that matches the titting on the exhaust manifold. At the top I simply screwed the standard Westerbeke exhaust injection elbow on. I don't have a siphon break because the injection point is above the waterline AND above the exhaust port on the transom.

[oakman]

Just wanted to update the thread and say thanks for all the input. Problem solved very nicely. This is the dry fit.

http://pic60.picturetrail.com/VOL1663/8744944/22231356/393163250.jpg

Oakman

[wizbang 13]

CHINA????!!!
missin a coupl o hose clamps?
Well, that is nice n short and I do think that is desirable.
Are we looking straight DOWN on it ? it would appear the camera is downside up?

[oakman]

No, this is the side view, I didn't check the image before posting, I'll have to flip it later.

As I said, this is a dry fit. 2 hose clamps per fitting now in place and works great.

China, I know, but they are ul listed.

[wizbang 13]

where the orange meets black, 'way de hoze clomp mon?"

[oakman]

This is a DRY fit, just put together to make sure it all fits. All the hose clamps are in place now, just not in the pic.

O

[wizbang 13]

sorry sorry ,I mixed up dry fit with dry exhaust in my brain

[oakman]

No problem at all, now I can put my stick away :D

O

[KAIROS]

http://pic60.picturetrail.com/VOL1663/8744944/22231356/393163250.jpg

I used a similar rig to keep the water input point far enough above my plastic Vetus box....and to raise the input point above the at-rest waterline to avoid siphoning. I have a longer nipple between the two elbows than you do.

My concern is that, at certain rpms, the motor movement (mostly side-to-side) whips this fitting around lots, and the bolts connecting it all to the motor/manifold are not engineered for this added weight and leverage. I am considering putting a bracket from the upper elbow over to an anchor point on the engine to help minimize the excess movement. But, I probably won't get to it until after it breaks loose once.

[oakman]

Kairos

I had thought of engine vibration and its effect. As this is relatively short, I am not very worried about it in this case, no real movement at the slower rpms where we get our worst vibration and these are seated very well.

However, if you can see movement than I would consider support, remember to plan your support in plane with your movement direction. ie side to side movement won't be helped much by a support in the vertical plane. Maybe you have already thought of that. Anyway, this is working great for me, very happy with the results.

O

[Ed Burnett]

That looks pretty good Oakman - maybe a bit of lagging on the dry section to prevent the underside of your cockpit sole beams getting too warm, but otherwise it's a neat solution.

[oakman]

Ed, thanks very much. Yes, lagging is in order and will be coming soon.

On another note I love this engine, laid up for a year, adjusted valves and decompression lever, turned over a few times by hand, couple seconds with starter, release decompression lever and fired up on the first revolution. Awesome!

O