View Full Version : 2 stage muffler question
06-26-2009, 01:05 PM
I'm thinking of getting a 2 stage muffler like the one shown here:
My exhaust setup is going to have the engine hook up to the muffler input. The output will go up and back for a distance of around 7 or 8 feet to feed into the top of a gooseneck which will then connect to the exhaust.
The hose is 2" and at 8 feet could theoretically and in the worst case hold just over a gallon of water that will come running back to the muffler when the engine stops. In this 2 stage setup I'm thinking all of this water will flow back into the top of the muffler where it will stay and not have a chance to slosh up the exhaust riser as the boat pitches. Also the new engine is lower in profile than the old hence a shorter exhaust hose coming out of the elbow. A muffler inlet that is positioned lower would help meet the requirement for the length of hose from the riser.
Does anyone have this type of muffler? Are you happy with it? Do you see any potential issues with this as opposed to a simpler water lift muffler?
Thanks for any good inputs.
06-26-2009, 01:14 PM
Vetus are quite good about replying to inquires, and they have sold LOTS of these. Sounds good for your instalation.
06-26-2009, 03:02 PM
I have about 12' of 2" exhaust hose from my engine back to a Vetus gooseneck. I used a large capacity Vetus LP50S waterlock muffler. It's worked fine and has been trouble free. The other advantage is that it costs less than the one you're considering. It's in the lower left corner here:
07-29-2009, 11:31 PM
Thanks for the suggestions.
I've been playing around with possible muffler setups. First, I found some installation guidelines from Centek here:
I have about 77 inches of hose giving 248 cubic inches of potential water. I'm converting volumes to cubic inches for easy comparison. Whatever muffler I get needs to hold at least this much water.
Per the guidelines there needs to be about 2 feet of hose between the engine and muffler for adequate mixing of water and exhaust gases. Also the drop from the exhaust to the top of the muffler needs to be about 12 inches. I think I can cut the first to 18" and be ok with it but I cannot skimp on the 12" neight requirement. It looks like I need to use a riser elbow to get extra height.
Behind the motor I have about 24 inches of working area measured fore to aft. From forward to aft the bottom of this area rises since it the inside bottom of the hull. The muffler needs to go directly behind the exhaust port so the hose is in a vertical plane parallel to the centerline of the boat. I can place a muffler close to the engine and get more height but the hose is shorter. Or I can put it further aft but it is higher and I need to add a riser elbow like the one here: http://shop.torresen.com/ships_store/?p=details&ident=148573&mfc=Westerbeke&sku=37403&prod_name=90+DEGREE+EXHAUST+ELBOW+RISER+KIT§ionid=10479
Now I list some options and pros and cons that I see.
1) kc8pql's suggestion: The LP50S - about 20" long. It will definitely hold sufficient water - 2.77 gallons or 639 cubic inches. However it is about 20" long and needs to lie fore and aft on a horizontal shelf. The hose between the exhaust and the muffler is going to be a bit short.
2) Vernalift 15R2200 - this is rectangular and roughly 12x7x7. It sits on a base so the actual dimensions are more like 10x7x5 inches. Deduct for the thickness of fiberglass and it is more like 250 cubic inches. I considered this when considering putting it forward in the space behind the motor. That would get me my 12" drop but maybe not enough hose between it and the engine. Also its volume is about what the downstream exhaust hose would hold. So it's out of the running.
3) The two stage muffler I originally asked about: I went ahead and ordered it. It came in and I looked it over. Just from looking at it and picturing how the water is going to sit and flow inside the unit it looks like its going to end up with a lot of water in the top half at all times when the engine is running. The bottom of it holds roughly 300 cubic inches. And so does the top. It would sit in the very back of the space behind the engine and require a riser.
4) I am also looking at a Centek 1500107 which is round 10.5 diameter x 10.16 high. It has a side in and top out hose connections. This holds roughly 700 cubic inches which is plenty. I can put it toward the back and use a riser elbow on the engine to get the required height and hose length. At the moment I am thinking this is the choice I will make. Or I could use a top in top out model.
5) I had considered making one. There's an article in Good Old Boat May/June 2007 that talks about this. If I did this it would be triangular to sit in the bottom of the area behind the engine to accomodate the aft rise and the deadrise in the hull. It is my desire to make one of the other options work so I don't do this.
Please comment if you see anything that would add constructively to the considerations here. Thanks.
07-31-2009, 07:53 AM
I went online and generated some graph paper with grids representing 1" and bolder grids representing 1 foot here:
I then measured the space and plotted it out on the graph paper so I can play around with various arrangements on paper. I can see where this website is quite useful for generating even esoteric types of graph paper that would be otherwise hard to find.
07-31-2009, 08:11 AM
You may be making this harder than it really is. You may have already seen this drawing somewhere else, but if not, it covers the bases well. It's from the Westerbeke installation manual. Stay at or above the minimums and you wont have any problems.
07-31-2009, 09:39 AM
You are probably right that I'm making it harder than it should be.
The 6" minimum height requirement shown between the exhaust outlet and the muffler is quite doable in my case with what I have on hand at this point.
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