Water "drop" muffler-replace with same??

[brad@elevated.org]

On my Cal 34, I have a muffler that looks nothing like the water lift mufflers--it is about the size of my heat exchanger (4"x16"). Exhaust enters at the bottom end--which is higher than the engine. Cooling water enters at the side-top of the muffler. Water-exhaust mix exits at the side bottom of the muffler. and drains straight to a thru-hull. I assume there is an internal riser that directs the gas to the top and a deflector cap at the top to keep the incoming water from getting into the exhaust inflow tub. So it seems to me that this is a completely different approach to getting exhaust and cooling water out of the system-hence my term water drop muffler.

Well the muffler broke from the connection to the engine exhaust pipe, so replacement time. I have no model to copy for a new water lift muffler and the whole concept of lifting water seems like it is ripe for getting it wrong.

Does anyone know where I can get a straight across replacement for what I have?

If not, is there a better diagram/description/how to design and install a waterlift than what I find in the catalogues (I haven't been to the boat to look at my Moyer repair manual)?

any help is appareciated

[rigspelt]

http://www.abycinc.org/committees/P-01.pdf
http://www.boatus.com/goodoldboat/Marine_exhaust.asp
http://www.yachtsurvey.com/exhaust_risers.htm
http://www.yanmarhelp.com/i_exhaust.htm
and a search for exhaust posts here in Don's forum might be of interest too.

[High Hopes]

Ever the divergent thinker, will putting the siphon break on the pump make for more trouble-free vacuum valve operation? Would the water pressure be higher right after the pump? Would breaking the siphon closer to the seacock, before the engine, be better?

[Don Moyer]

Steve,

As a short answer, I'm not sure, but I don't think so because it places the whole engine in the downhill side of the suction loop of the system, which seems to me will dampen the negative pressure surge necessary to reliably open the anti-siphon valve.

For a longer answer: One of the biggest problems in designing a successful siphon break is that the valve (which is nothing more than a very low head one-way check valve) has to operate in such a very low pressure environment - in both suction and positive pressure. One-way check valves tend to operate much more reliably in systems involving high negative and positive pressure to sequentially suck them open and slam them closed. Anti-siphon valves have neither.

The first valve we used in our anti-siphon kits many years ago was a little "0" head valve which used a small Delrin disk (a type of plastic) with no springs involved. This valve worked very well to open and allow the downhill side of the water hose to suck air into the line when the engine was shut off, but it didn't handle the second function of a good anti-siphon valve very well, which is to close (under very low positive pressure) when you start the engine so that engine cooling water won't flow back out through the valve and into the bilge all the time the engine is running. If an anti-siphon valve doesn't do the second part of its job well, you can actually find your boat sinking under your feet unless you have a good warning system to warn you that you're taking on serious water as you're motoring along.

Back to your sketch; I think that elevating the loop above the water line (to block hydrostatic flow) after the engine (as in the conventional way) allows the weight of the water in the downhill side of the water hose to act more directly on the anti-siphon valve rather than having to suck through the entire engine to open the valve.

As a somewhat separate but related matter, you should always plumb the hot section of the exhaust system as high as possible between the back of the manifold and the point where you introduce the engine cooling water. If you can get that part of the hot section higher than the theoretical water line, it reduces some (but not all) of the risk of a failed anti-siphon valve. I'll attach a pdf file of our generic sketch that tries to show this feature.

Don

[Don Moyer]

I don't know if you've seen our generic sketch or not. I'll try to attach it to this message.



Don

[High Hopes]

it places the whole engine in the downhill side of the suction loop of the system, which seems to me will dampen the negative pressure surge necessary to reliably open the anti-siphon valve.

Rats. Makes perfect sense to me. Oh well.

I suppose the best answer is to make sure the seacock valve is closed when docked, install a bilge alarm, and to use a siphon break for decenecy sake.

Steve

[High Hopes]

you should always plumb the hot section of the exhaust system as high as possible between the back of the manifold and the point where you introduce the engine cooling water.

Don,

My engine exhaust system uses a water jacketed pipe. At least that's what I think. I can not find any design descriptions of this pipe. Here is a more accurate drawing of the exhaust system on my boat. I assume the top of the pipe has something like a anti-siphon trap inside, like the kind you used to see on kitchen sinks with dishwasher drain connections.

Steve

[Mark S]

Steve,

That's what my exhaust system looks like. My surveyor told me that it is an older design and suggested in his survey that it looked to be original equipment with the engine and that it be replaced with "an elevated riser, water lock muffler, and reinforced exhaust hose." He called the vertical piece to which you call attention in your diagram a "standpipe" and I believe it is the functional equivolent of a stack in a residential plumbing system. My exhaust system functions perfectly and so long as that's the case replacement is way down on my list of things to do.

Mark

[High Hopes]

Hi Mark,

You may never need to replace it. I found some information on the net about someone who brought his standpipe to a welder because he wrenched off a fitting. The machinist was amazed as the inside pipe was bronze. The outside is copper. The machinist said, "Don't even think about replacing this."

Here is an updated picture that shows how it works. The dark blue, to medium blue, to lighter blue is the heating water; the bright red to dark red is the cooling exhaust.

Steve

[Don Moyer]

Steve,

I can't be completely sure what happens at the top of your riser pipe, but in general, it has to involve a way (hopefully safe way) for the water to get from the water jacket to the exhaust path to leave with the exhaust.

Unless I'm missing something, as long as the inner pipe remains intact, your system should be completely safe. However, if the inner pipe should corrode through, the water will have a direct path to the inside of your engine in the same manner that exists in the earlier Pearson fleet of Tritons and Vanguards.

Don

[Don Moyer]

Sorry, Steve, I forgot to comment on your question regarding anti-siphon protection. I would agree that the pathway from your water jacket to the exhaust path appears to be well above the waterline, which poses no immediate siphon potential.

Don

[Mark S]

Hi Steve.

Once again, a great diagram. So much for my thinking the standpipe was a stack. The standpipe must be sealed at the top or exhaust would vent inside the boat, and the exhaust tube out of the standpipe must be wide enough to provide whatever atmosphere is necessary at the top of the standpipe. I knew the outside is copper but I didn't know the inside is bronze. My surveyor seemed dubious about it although he found no defect and stated no reason other than its age for suggesting its replacement. Made of those materials, it ought to continue working well for quite a while, as should yours.

Mark

[Mark S]

Now I see Don's replies. I wonder how one inspects the inner pipe?

Mark S

[Kelly]

Maybe a description of my exhaust system coupled with some photos will help with visualizing your set-ups. I, too, was amazed at the lack of corrosion or wear once I had everything disassembled and cleaned up.

Photo 1) Wrapped hot exhaust (iron pipe) entering the bottom of a riser. Cooling water is injected into the riser at the lower fixture just visible at the bottom of the photo and circulates around the central hot exhaust pipe before arriving at the muffler/mixer.

Photo 2) Same, disassembled and cleaned up.

Photo 3) Riser arriving under the mixer. Wrapped pipe is the continuation of the hot exhaust system after the cooling section while the small copper pipe carries the cooling water from the riser up to the top of the mixer.

Photo 4) Mixer cleaned up.

Photo 5) Looking down into the mixer. The center pipe is for the arriving hot exhaust while on the right you can see the "crown" that sits over the top of the arriving hot gases and allows the cooling water to arrive in a "shower" configuration over the top, without entering the hot pipe. The mixed water/gases exit the chamber about half-way up the side and then head for the transom, staying above water line the rest of the way.

As you see, this older system (1964) is constructed of extremely solid/thick copper. The only problematic pieces were the attaching hardware.

Hope this helps.

Kelly