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Old 09-23-2021, 02:44 PM   #1
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Waterlift Muffler (Loop or not to loop?)

Good day!

I'm back with another questions about the mysteries of my vessel that we're in the middle of refit on up here in Southeast Alaska.

As we are tearing through systems we are discovering (or realizing) quirky things that I'm wondering if I can get some clarification on.

Our STBD waterlift muffler has a loop in it and attaches from the top before heading aft and out the exhaust port on the transom. However, to our surprise the PORT side attaches low to the side of it's waterlift muffler and has no loop on it at all. Just a straight shot aft and out the transom.

To further confuse us - there is a 1.5" exhaust hose that is spliced into the port main exhaust line (aft of the waterlift muffler) that bypasses the port waterlift muffler altogether and goes into the engine room (below the waterline) where it attaches to a much smaller waterlift muffler for the generator.

The generator was removed as it was a huge ball of rust and was no longer working (surprise, surprise) and a co-captain reported possibly seeing drips from the 1.5" exhaust hose during an engine check while underway during our vessel delivery from Seattle.

Wouldn't the splice bypassing the waterlift muffler be a big issue for water intrusion? Why would there be a loop on one side but not the other?

We can't make sense of the previous owners work.

As always, I appreciate the insight and help!

Kyle
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Old 09-23-2021, 04:35 PM   #2
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WaterLIFT mufflers typically have inlets on top or in the lower part of the muffler body, and outlets out the top or the upper part of the muffler body.

Best practice would call for raising the outlet run as high as practical (max 4ft conservative) to make the exhaust quieter and reduce the possibility of backflooding.

Not sure I follow your gen setup, but:

Combining generator exhaust and main engine exhaust should be frowned upon for a variety of reasons. One common treatment is to dump the gen exhaust into the main near the transom outlet. This creates a megaphone effect with the gen exhaust when the mains are off.

These are separate systems, maybe with different backpressure limits, and gas and water flows. They should be plumbed seperately.

It's just bad practice to combine these exhaust systems, and whatever reason for it, just doesn't fly.

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Old 09-23-2021, 04:49 PM   #3
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Generator exhaust into main exhaust can cause CO and other gases to pass thru one of the main cylinders and into the engineroom if the main isn't running. Depending on the muffler, etc. I'd remove the old generator line.

The two mufflers and exhaust should be exactly the same if the engines are the same. Otherwise they wear differently.
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Old 09-24-2021, 11:43 AM   #4
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I appreciate the help. It seems common sense to me that they should both be the same (because, yes, they are the same engines) but sometimes I have to stop and ask myself if I'm looking at the full picture. Then a seemingly simply concept gets a little murky.

I've attached a rough go at diagram I've whipped up to better explain the setup. The main waterlift mufflers are at or a couple inches below just the waterline. The exhaust is submerged at the outlet on the transom.

I don't pretend to know everything about exhaust system design but this is too strange to me.
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File Type: pdf Waterlift Rough Diagram.pdf (161.7 KB, 33 views)
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Old 09-24-2021, 12:23 PM   #5
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A sketch showing the engines and exhaust elbow would be helpful.
If the muffler if below the waterline, and the exhaust is at or below the waterline, then you need a riser coming out of the muffler at least 18" above the waterline. I believe the 'loop' sort of accomplished this.)

From the riser the exhaust hose would slope down to the exhaust port. This will eliminate any back filling of the muffler, and prevent any potential siphoning that might end up flooding your cylinders if the engine doesn't start.

Google design of waterlift muffler systems and you will find a number of images that display this concept. Centek makes a number of splices and 90 elbows to make the design possible. Exhaust hose is obscenely expensive but all you need are the riser pieces. (with an unknown configuration between exhaust elbow and muffler)
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Old 09-27-2021, 11:53 AM   #6
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Here's a look at the port side splice I was talking about. The Y split goes to PVC (which bypasses the lift muffler) leads into the engine room where it drops down to a smaller waterlift for the generator. The main waterlift muffler (at the waterline, photo #2) is in a closet and shows no loop. It goes through the bulkhead into the engine room where it tilts downward and attaches to the port engine exhaust . I didn't have a chance to get photos of that yet but I will post as soon as I can.

I don't see how water can't flow back into the engine in a following see or in a roll at anchor.

Insight? Thoughts? Appreciate it!
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IMG_3014.jpg   IMG_3015.jpg  
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Old 09-27-2021, 12:31 PM   #7
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Quote:
Originally Posted by Keysdisease View Post

Best practice would call for raising the outlet run as high as practical (max 4ft conservative) to make the exhaust quieter and reduce the possibility of backflooding.

Not sure I follow your gen setup, but:

Combining generator exhaust and main engine exhaust should be frowned upon for a variety of reasons. One common treatment is to dump the gen exhaust into the main near the transom outlet. This creates a megaphone effect with the gen exhaust when the mains are off.

These are separate systems, maybe with different backpressure limits, and gas and water flows. They should be plumbed seperately.

It's just bad practice to combine these exhaust systems, and whatever reason for it, just doesn't fly.

$0.02
Quote:
Originally Posted by Lepke View Post
Generator exhaust into main exhaust can cause CO and other gases to pass thru one of the main cylinders and into the engineroom if the main isn't running. Depending on the muffler, etc. I'd remove the old generator line.

The two mufflers and exhaust should be exactly the same if the engines are the same. Otherwise they wear differently.
My genny exhaust is plumbed and designed this way. I have found it quitter and you can hardly hear it running. The genny exhaust runs through a wet muffler, then dumps into the port engine exhaust.

As for safety, no one should be swimming near the exhaust of a running generator.
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