Aboard Astraea

Invest in experiences, not things

Engine Difficulties

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One of the hardest things to deal with on a sailboat doesn’t have to do with the masts, sails, or the rigging. It’s the darn engine. It’s how we get in and out of the slip, charge the batteries and keep the fridge cool when we’re away from the dock. We use it once or twice a week to go to the pump out dock to get rid of our waste water. Right now if Astraea is without an engine we’re out of luck.

Since the engine is so important to running the boat there has to be a problem with it. The engine exhausts air and water to a water lift muffler that mixes the two and then pushes it overboard. The current water lift muffler is made out of stainless steel and lives underneath the water heater down in the bilge. Two weeks ago, after our trip to LaPlaya, I had to run the bilge pump to empty water out of the bilge. At the time, I thought maybe I needed to repack the packing gland around the propellor shaft like I did on Airborne in June. Last week we took a trip over to Fiddlers Cove Marina so I could be race committee with Navy Yacht Club. On the trip back the high water level bilge pump alarm went off letting me know we had a lot of water in the bilge. I found water leaking from our water lift muffler. I patched the hole I could see with putty so we can keep using the boat. It slowed the leak, but doesn’t completely prevent the water and exhaust from escaping.

First off, how does this water lift muffler thing work? Take a look at the diagram below.

A water lift muffler. Credit: http://mintoart.com

Here’s how it works. The engine discharges the raw cooling water mixed with exhaust through a hose in to the water lift muffler. Water collects in the bottom and the pressure from the exhaust forces the water up and out through a pipe inside the water lift muffler and eventually out through the hose to the overboard discharge. Pretty simple. Once the engine is turned off any water left in the engine exhaust and overboard discharge hoses drain down in to the water lift muffler.

Since the old stainless steel water lift muffler failed after about two and a half years I decided that a better solution would be to replace it with one that won’t corrode away while we’re cruising. I’m replacing it with some trepidation because Astraea has had two new Westerbeke engines installed by the previous owner. The first engine was ruined because of an improperly installed exhaust system. The water lift muffler wasn’t large enough to hold all the discharge water left in the engine exhaust and overboard discharge hoses so water backed up in to the engine.

Things start to get nerdy here because I’m talking about math, so read on if you’d like to see how I figured how large of a water lift muffler I need.

To prevent water from backing up in to the engine, a new custom 5 gallon stainless steel water lift muffler was installed. I did a calculation on the volume required for the water lift muffler by finding the volume of water that could be in the hose. The formula is Πr² * h. For my installation the hose is 2 inch internal diameter, or 1″ radius. There’s 21 feet of hose from the engine to the overboard discharge so to keep everything in the same in the same units 21 feet * 12 inches is 252 inches. Π is reasonably rounded to 3.14159 for this calculation. Now substitute and solve. 3.14159 * 1 * 252 = 791.6. OK, that’s good, but how many gallons is that? I used google to convert that volume in cubic inches to gallons and got that it’s just shy of 3.5 gallons.

Now I had to find an appropriately sized water lift muffler that would fit the bilge. I went to West Marine and asked about water lift mufflers from Centek after looking online and not finding an appropriately sized one. Today I eneded up ordering a 4.5 gallon water lift muffler from Vetus Marine. The extra gallon of capacity will be a safety buffer. This water lift replacement job is going to be a big one, so stay tuned to see how it turns out.

Don’t worry, we still have fun! Natalie and I took a walk to Pepper Park by our marina with Sullivan and Koku. We played on the swings.

Comment

8 Comments

  1. Thanx for sharing … however, the engine video is “private” and we can’t see it! However, we did see Natalie and Sullivan swinging … how did Sullivan like the swing?

    Hope all your calculations are correct and all will be fixed soon! Wish we could help!

    Hugs!

  2. Water lift muffler leak video works!

  3. Just goes to show that even a brand new engine isn’t free of problems, sadly.

  4. At least you are discovering these problems now .. instead of 2 years from now! You’ll get things in good working order for your “dream sail”!

  5. I am trying to learn the systems on boats as well and the water lift muffler is an interesting component. The question I wanted to ask is inside the muffler itself, the tube in the muffler that feeds the overboard discharge line. How far above the bottom of the muffler does this tube sit. It seems that the best the muffler can do it empty down to that level, say a remaining 1/2 gallon and your 3.5 gallons would refill on top of that. Just want to make sure your extra gallon of room in the tank is sufficient. Thanks for the explanation of the workings of the muffler. –Dan

    • I haven’t taken apart my old muffler yet. I will take it to Cogswell Marine in San Diego for them to look at. The new muffler has a check valve to prevent water from coming back in to the engine too. My biggest concern is if the engine doesn’t start and I need to drain the muffler. The drain will be buried deep in the bilge where I can’t reach it so I’ll need to devise some kind of hose setup to get the water out.

  6. Hi,

    This is to inform you that you are using my artwork (water-lift muffler) without permission. I’m not opposed to the use of my illustration as content of your blog, but I would like proper credit. Mirto Art Studio owns the artwork, not Power & Motoryacht. Please credit http://www.mirtoart.com, with a link to my website. The same applies to any other illustrations that you may have used.

    Please confirm receipt of this notice and your intention.

    Thank you,

    Paul Mirto
    Mirto Art Studio

  7. Paul: Thanks for letting me know about your art. I’ve credited it properly now.

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