Water in Cylinders

Jan 30, 2012
1,093
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
The waterlift is a muffler for sure. Exhaust gases are mixed with water inside the chamber and noise is reduced.

More important - the waterlock chamber also accommodates all the water in the large tubes that go from the waterlock to overboard.

When the motor is shut off, there is water in the tubes downstream of the waterlock discharge. That water flows back into the water lock chamber - thus the backflow water volume gets stored/trapped/contained within the waterlock chamber itself. If there were no waterlock that water would flow back onto the the motor instead.

So the waterlock attenuates noise when the motor is running and (more important) stores surplus water when the motor is turned off thus protecting the motor from water back flows.

Charles
 
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T Dunn

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May 23, 2018
16
Allied Princess Southwest Harbor
You might want to check the siphon break on the raw water line between the heat exchanger and the injection point into the exhaust line. If that siphon break is plugged you could easily siphon water into the engine. Of course since your exhaust exits below the waterline (a stupid design if you ask me) you could also siphon water in that way. If it was my boat I would raise the exit point so that it was always above the waterline and glass over the old exhaust exit. My exhaust exits the boat near the bottom of the transom more than a foot above the waterline where it is never submerged unless the boat is seriously pooped - hasn't happened yet.

Also if you have a waterlift type muffler, the muffler should be sized so that all the water in the hoses can drain into it without filling it. 1.5" hose can hold up to 0.092 gallons per foot and 2" hose can hold up to 0.16 gallons per foot.
 

RoyS

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Jun 3, 2012
1,216
Hunter 33 Steamboat Wharf, Hull, MA
Thank you, Tom. In my case there is no vacuum break in the cooling water line, however, that injection point is above the waterline. Water cannot siphon in that case. The hose volume to lift muffler volume is an issue as it is with most boats. I took some of the advice offered in this thread and ordered a cast stainless exhaust elbow by HDI that raises the spill point into the engine by about 6". I ordered a 2" exhaust elbow to replace the large bent hose loop where the exhaust exits under the boat. After these modifications the engine spill point should be about 4" above the exit spill point and gravity should drain exhaust system before it floods back into the engine. Still unsure about the vented loop. With the engine off, seawater cannot drain without breaking the vacuum at the engine exhaust elbow. On the other hand seawater cannot reverse flow toward the engine without venting the air in the elbow. Still pondering that. Remember, I have owned this forty year old boat for almost twenty years and there was only the one hydrolock event and that was after I lowered the idle speed and stopped revving the engine before shutdown. I do not think that many boats meet the hose volume to lift muffler volume that you (and others) describe. A typical lift muffler holds less than 1 gallon of water. Using your calculations, that translates to no more than 6 feet of exhaust hose. Most boats, including mine, have more than 6 feet of exhaust hose.
 
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Feb 14, 2014
5,714
Hunter 430 Waveland, MS
On the other hand seawater cannot reverse flow toward the engine without venting the air in the elbow.
Engine off, sailing in heavy seas, can back flow water in your exhaust loop and into your open engine exhaust valve.
Jim...
 
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RoyS

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Jun 3, 2012
1,216
Hunter 33 Steamboat Wharf, Hull, MA
James, ABYC and others advocate a 1' high raised loop in the exhaust hose before exiting at the transom. The reason given is in case following large seas enter the exhaust hose at the transom, the 1' loop is supposed to prevent that. However, in my case, like it or not, my exhaust exits about 1" under the sea level through a port on the hull bottom. I do not think the following seas scenario applies here. In addition there is a lift muffler between the engine and the exhaust exit. Still working on this problem.
 
Jun 25, 2004
288
Hunter 306 Pasadena MD
I think all this about “the exhause must exit above the waterline” is not correct. Lots and lots of boats have a below waterline exhaust exit. Like almost all modern production sailboats.
 
Feb 14, 2014
5,714
Hunter 430 Waveland, MS
Lots and lots of boats have a below waterline exhaust exit. Like almost all modern production sailboats.
No issue on Bellow Waterline Exhaust except that I expect the comforting "Spit" that is basically water flow detection.

New models can even have a water flow meter installed.;)

No muffler is needed as long your exhaust is below waterline.
Jim...