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Old 08-11-2022, 04:21 PM   #1
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2000 Mainship 39, waterlock muffler

Hi All: I had posted in the Spring about having my Cat 3126 Diesel engine rebuilt due to hydrolock. I received a number of work arounds to avoid this occurring again, as the exhaust lends itself to sea water backing up into the turbo injectors when the engine is not running, so thank you to all that responded. I am still trying to source a more permanent fix and would like to know if any one has had any history with installing a Vetus Waterlock type MGS, MGS6456A. Alternatively I have seen a custom fibreglass waterlock muffler but there is no name or identifying numbers on the actual muffler, hence thinking this Vetus model may do the trick. Much appreciate any feedback. Sovereign
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Old 08-17-2022, 01:20 AM   #2
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Lacking necessary details for diagnosis, I’d say you have an exhaust engineering problem that must be addressed now.
A water lock muffler is not going to change the way gravity works.
The only real solution is to build a dry riser that is high enough to raise the spillover height to 12” or more above the waterline.
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Old 08-17-2022, 07:18 AM   #3
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Yes a dry riser as high as possible is the only reliable solution. You could also add a surge tube.
This has been a design problem on the 390s when they started putting the 3116 engines in these boats.
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Old 08-17-2022, 07:41 AM   #4
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Extending the riser so it is at least 12" above the water line is one solution, but there may not be room and it is expensive. But it is what I did on my MS Pilot 34 and solved the problem.

But there may be a cheaper way. On the MS 34T which I owned for several years and is a successor of sorts to the 390, it has a conventional water lift muffler with the bottom located near the water line. If water were to build up in that muffler, it could go over the riser and into the engine. But Mainship installed an equalization line, a 3/4 or maybe 1" hose that is attached near the bottom of the water lift muffler and exists the side of the hull near the water line.

This equalization line assures that the water in the muffler can never go above the water line outside. Most mufflers, at least Centek's have a nozzle built in for this purpose. You just remove the plug, attach a barb fitting and hook up the hose. It probably would require a haul out to install the hull penetration.

There are other band aids available like a surge tube which absorbs each slug of water coming in the exhaust hose but these are not as positive as the riser height increase or the equalization hose.

And FWIW I looked at the Vetus you mention. It is no different functionally to the Centek which is what I expect that you already have. Yes it has an angled outlet and the top rotates to make hose connections more straightforward, but functionally, it does the same thing as the Centek.

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Old 08-17-2022, 11:00 AM   #5
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Quote:
Originally Posted by kapnd View Post
Lacking necessary details for diagnosis, Id say you have an exhaust engineering problem that must be addressed now.
A water lock muffler is not going to change the way gravity works.
The only real solution is to build a dry riser that is high enough to raise the spillover height to 12 or more above the waterline.
I installed Centek (vernalift) waterlift mufflers with exit hose that is well above the waterline before it takes a 90 turn to long down sloping exhaust hose. Maybe not 12" above WL but close. No risk of hydrolock.
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Old 08-17-2022, 01:21 PM   #6
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Hi Kapnd, much appreciate your info, unfortunately I do think my space is limited to look at installing a riser, I have very little room in the engine compartment, and have even looked at removing one of my water tanks and generator to install a riser that would sit nicely in the space under the stairs to the fly bridge. I’ve decided that was a bad idea. At present the exhaust hose coming off of the turbo cooler only has space to angle down about 15 degrees at most. But thank you for your input, it’s great having the ability to ask questions.
Nancy
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Old 08-17-2022, 01:39 PM   #7
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Hi David: hey, I hadn’t heard of an equalization line, and from your own experience it seems that it was a fix. I actually don’t think that I have a waterlock muffler, looking at my system the exhaust hose runs off of the turbo cooler, and angles down about 12-15 degrees for about 3 feet and then hooks onto a rigid 6” plastic pipe, that looks about 8 feet long, which I believe then exists the boat. I have seen a fibreglass waterlock muffler, which I assume was custom on a 2002 Mainship, the boat is at the same Club as I, unfortunately the owner does not know who installed the fibreglass muffler, and it is all one piece, there is no removable parts to see how the exhaust is vented inside.
I will be hauling out in October, in the interim I will check out further how one would go about installing an equalization line.
Great info, thank you
Nancy
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