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Old 10-05-2024, 22:26   #1
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Following seas flooding engines

L40 when sailing with following seas and wind 120 to 180 especially on the starboard side have found water is coming up the exhaust .. some people are trying to tell me that is from the cooling water not having a siphon loop. That small amount of water from the heat exchanger tubes that might possibly trickle in the muffler is nothing compared to what can be stuffed up that exhaust by a hard following seas.. there's some other posts and threads in other sections people experiencing this. Considering exhaust flaps but facing the wrong way they become a scoop. Is the wave coming up from the bottom as the boat goes down from the back from a wave breaking on quarter ?? There is also some good illustrations on good exhaust design like the North Sea system that has a poor on both sides and the water can flow through while the exhaust has to come down from the top into that passage. I'll be the best but not the easiest solution. Some experts talk about putting a valve to close the exhaust outlet.. in the meantime I know when I'm sailing in that position I'm running that engine. ...
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Old 11-05-2024, 02:02   #2
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Re: Following seas flooding engines

The exhaust hose needs to loop well above the waterline on all points of sail and load. Sailboats are challenging because the engine is often low in the hull, the exhaust outlet is often mounted off the centerline which makes it more vulnerable on one tack, and getting the exhaust loop high enough is difficult or ignored (note, exhaust loop vs vented loop). An exhaust flap or check valve is not a substitute for proper exhaust installation.

See attached picture from a Northern Lights white paper "Don't Drown Me."

https://www.northern-lights.com/media/PDFs/misc_pdfs/dont_drown_me.pdf
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Old 11-05-2024, 02:52   #3
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Re: Following seas flooding engines

Thanks mvweebles.

“Please Don’t Drown Me” ~ Northern Lights Technical Information Paper [© 2017]
Important Exhaust System Installation Information
https://www.northern-lights.com/medi...t_drown_me.pdf

See also: “Risk of Engine Drowning” ~ by Steve D'Antonio, ‘PBB’ 2010
https://www.proboat.com/2010/03/risk...gine-drowning/
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Old 11-05-2024, 04:19   #4
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Re: Following seas flooding engines

Quote:
Originally Posted by GordMay View Post
Thanks mvweebles.

“Please Don’t Drown Me” ~ Northern Lights Technical Information Paper [© 2017]
Important Exhaust System Installation Information
https://www.northern-lights.com/medi...t_drown_me.pdf

See also: “Risk of Engine Drowning” ~ by Steve D'Antonio, ‘PBB’ 2010
https://www.proboat.com/2010/03/risk...gine-drowning/
Steve D's article references back to Northern Lights article written by Bob Senter of Northern Lights. Two people who are top respected experts in marine construction. Steve frequently seeks input from Bob on mechanical topics.

My favorite quote from Steve's article is "don't assume it is correct just because it was originally installed by manufacturer."
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Old 11-05-2024, 05:20   #5
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Re: Following seas flooding engines

Quote:
Originally Posted by yachtski View Post
L40 when sailing with following seas and wind 120 to 180 especially on the starboard side have found water is coming up the exhaust .. some people are trying to tell me that is from the cooling water not having a siphon loop. That small amount of water from the heat exchanger tubes that might possibly trickle in the muffler is nothing compared to what can be stuffed up that exhaust by a hard following seas.. there's some other posts and threads in other sections people experiencing this. Considering exhaust flaps but facing the wrong way they become a scoop. Is the wave coming up from the bottom as the boat goes down from the back from a wave breaking on quarter ?? There is also some good illustrations on good exhaust design like the North Sea system that has a poor on both sides and the water can flow through while the exhaust has to come down from the top into that passage. I'll be the best but not the easiest solution. Some experts talk about putting a valve to close the exhaust outlet.. in the meantime I know when I'm sailing in that position I'm running that engine. ...
Hi, what yacht is that? Have seen Lagoon and Leopard 40’s referred to as L40, along with some others. Year??
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Old 11-05-2024, 07:05   #6
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Re: Following seas flooding engines

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Originally Posted by yachtski View Post
L40 when sailing with following seas and wind 120 to 180 especially on the starboard side have found water is coming up the exhaust .. some people are trying to tell me that is from the cooling water not having a siphon loop. That small amount of water from the heat exchanger tubes that might possibly trickle in the muffler is nothing compared to what can be stuffed up that exhaust by a hard following seas.. there's some other posts and threads in other sections people experiencing this. Considering exhaust flaps but facing the wrong way they become a scoop. Is the wave coming up from the bottom as the boat goes down from the back from a wave breaking on quarter ?? There is also some good illustrations on good exhaust design like the North Sea system that has a poor on both sides and the water can flow through while the exhaust has to come down from the top into that passage. I'll be the best but not the easiest solution. Some experts talk about putting a valve to close the exhaust outlet.. in the meantime I know when I'm sailing in that position I'm running that engine. ...
A siphon is a different problem than waves induced flooding. If a boat has an engine below the load waterline and was built without a siphon break, it is highly unlikely that the builder got anything else right.

The FIRST cure that must be applied to the wave problem is to loop the incoming exhaust as high as possible. Different engine makers will have different limits on how high you can go. I have seen from 4 feet to 6.5 feet. Unfortunately, some boats are designed that even small amounts of lift here are difficult or impossible to achieve. Only after that has been done should other fixes be applied.

An external flap works if of good quality and maintained well. Some waterlifts also have internal flaps that help keep water from pushing through in quantity.

Even with good quality system components and designs under some "lively" sailing conditions water can slowly make its way in. It is a good idea when sailing in rough conditions to start the engine every 24 hours or so to blow out any accumulating water, or leave the drain on the waterlock open if you are going to be sailing for an extended time.
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Old 11-05-2024, 11:11   #7
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Re: Following seas flooding engines

I have had to custom make exhaust elbows to get the height needed at the water injection Go as high as you can. In my Pearson 30 I have a 36 inch lift from my muffler to the final hose out the transom and a flap there that has been holding out well for 7 years.

Sounds like it was never installed right.
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Old 14-05-2024, 12:25   #8
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Re: Following seas flooding engines

Very true and can be confused leopard 40 2019.
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Old 14-05-2024, 12:34   #9
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Re: Following seas flooding engines

Thank you all for input. Although everything that you have posted is pretty redundant I have installed many generators in boats and fully aware of the don't drown me by one of my favorite generator company Northern lights. The issue is only as I stated in a following sea where the water comes way over the exhaust outlets. Elsewhere in this forum people have talked about installing valves to close off your exhaust when in such conditions. But that can be an issue in itself as we all know. I am seriously considering raising the outlet , Or the loop on the inside as high as possible. Otherwise I am considering a drain from the muffler to a container with a bilge pump...
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Old 14-05-2024, 13:01   #10
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Re: Following seas flooding engines

I'm of the opinion that any water-lift muffler should have a drain on it.
It's the right thing to do, no excuses, no ifs, ands, or buts.
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Old 15-05-2024, 02:13   #11
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Re: Following seas flooding engines

Quote:
Originally Posted by yachtski View Post
... I am seriously considering raising the outlet [min. 6" above WL], Or the [vented siphon break] loop on the inside as high as possible [min. 18" above WL]. ...
Raising both, would be a good idea.

Or, you might, if space allows, try a “North Sea Exhaust” [Transverse] system, where the exhaust exits through [both P & S] the hull sides , rather than stern transom.
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Old 15-05-2024, 03:12   #12
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Re: Following seas flooding engines

Quote:
Originally Posted by yachtski View Post
Thank you all for input. Although everything that you have posted is pretty redundant I have installed many generators in boats and fully aware of the don't drown me by one of my favorite generator company Northern lights. The issue is only as I stated in a following sea where the water comes way over the exhaust outlets. Elsewhere in this forum people have talked about installing valves to close off your exhaust when in such conditions. But that can be an issue in itself as we all know. I am seriously considering raising the outlet , Or the loop on the inside as high as possible. Otherwise I am considering a drain from the muffler to a container with a bilge pump...
The only issue with exhaust outlet being submerged is back pressure. Many exhaust systems are designed with submerged outlets to reduce noise, including very large engines on sport fishers. As long as the loop on the exhaust is high enough, water into the engine isn't a problem except in potentially extreme submerged situations (e.g. boat is sinking). As others have said, siphon loop is a different topic altogether.

BTW, the most effective flap on an exhaust I've seen is a 12-ibch length of inner tube. Collapses when pushed from astern. Looks hokey, but works well.
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Old 15-05-2024, 04:57   #13
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Re: Following seas flooding engines

Quote:
Originally Posted by mvweebles View Post
...
BTW, the most effective flap on an exhaust I've seen is a 12-ibch length of inner tube. Collapses when pushed from astern. Looks hokey, but works well.
Hose, used in wet exhaust systems, shall comply with the performance requirements of SAE 12006 or UL 1129. All other exhaust system components shall meet the performance requirements of UL 1129.

"Inner Tube", effective though it may be, in preventing back flooding, will NOT meet the required 'standards'.

“Internal Combustion’s Backside” ~ by Steve D’Antonio, in ‘PBB’, Dec/Jan 2018
For new and refit vessels, here are the fundamentals of exhaust system design and analysis.
https://stevedmarineconsulting.com/w...s170-FINAL.pdf

ABYC P-01 [very old version]:
“P-l INSTALLATION OF EXHAUST SYSTEMS FOR PROPULSION AND AUXILIARY ENGINES” ➥ https://law.resource.org/pub/us/cfr/....P-01.1993.pdf
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Old 15-05-2024, 10:42   #14
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Re: Following seas flooding engines

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Very true and can be confused leopard 40 2019.
SAW IT ON A LAGOON, WITH THE BOAT IN GEAR AND NO FOLDING PROP...
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Old 17-05-2024, 10:25   #15
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Re: Following seas flooding engines

I have an IP29. An Island Packet. When I first bought the boat, I was delivering it home from NYC to the Cape, and the weather got real nasty. Following seas. The boat started taking on water, and we couldn't figure out where it was coming from. We were sinking. Both bilges clogged up. Eventually, after calling the Coast Guard, they followed us to port, and then helped us pump out the water, which was just below the floorboards. The boat stayed dry!
A mechanic searched hard for the problem, Eventually, he found that both hoses leading from the cockpit skuppers to the stern had corroded on the underside of the hoses. Water had come in, after hitting the stern repeatedly, and just drained into the boat. Surveyor never saw the cracks because they were on the underside. A good lesson. We replaced them, and it's been fine sailing since. I'll be sure to check them and carry spares when I go cruising.
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