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Old 18-02-2021, 21:51   #31
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Re: Do you have an exhaust out the midship side?

Yes Pelagic very similar looking yacht this build is a Bollard. Excellent information thank you. Pelagic may I ask do you have a blog or anywhere I can see a photos of your deck and rigging for ideas too please? Thank you John (Auspain) Go Diving Western Australia
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Old 18-02-2021, 23:27   #32
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Re: Do you have an exhaust out the midship side?

My generator exhausted midship no worries at all all
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Old 19-02-2021, 02:54   #33
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Re: Do you have an exhaust out the midship side?

A side exhaust for a generator is problematic for two reasons.

Wave slap can jet water through the exhaust hoses even with a loop up to the level of the deck. Remember that the exhaust hose run is short, half the width of the hull. The wave jet can eventually flood the exhaust system resulting in sea water in the cylinders via an open exhaust valve.

When the boat heels and rocks, excess sea water in the exhaust hoses and water lift can drain into the head.

The head and valves eventually corrode and fail. Hydraulic lock was not seen because an exhaust valve is only open on the up-stroke.

There is a exhaust exit fitting with a rubber flap having beveled sides that can be purchased to minimize the problem however we found that it may not make a perfect seal.

A side exhaust system needs to be well engineered to give trouble free use. Ask me how I know!
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Old 19-02-2021, 03:11   #34
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Re: Do you have an exhaust out the midship side?

Quote:
Originally Posted by auspain View Post
All the replies have been excellent and I am very grateful for your time and input. The vessel is a steel 60' (18m) motorsailor ketch yacht and is currently 42 tonne when loaded 50. Building started around 1980 and was never finished by the builder and or launched. I have been working for the past few years making the required changes to meet commercial survey standards. An issue I ran into with the survey is running the exhaust under accommodation to the transom. If run through accommodation spaces the hose must be in a redundant gas tight housing. I was prepared to do this, however both the surveyor and a retired marine servicemen have said put it out the side. Which saves a lot! Except I have not been able to find anyone until now that had done it and was concerned about fumes on deck. The vessels engine room is mid ship under a bridge deck which makes up 1 of 3 watertight compartments. And if anything was to fail its defiantly in the engine room where I would like it to happen where its accessible.
Surprises at the focus on fumes in this thread. Very little mention of what is the best operational configuration that allows the engine to breath and not risk backup with water. It can be very difficult to correctly run exhaust out the transom.

OP has two professional opinions recommending side exhaust. Gordmay offered a diagram of a North Sea Exhaust early in this thread.

Exhaust system issues are more common than most think. Whenever I hear of a sucked valve or similar, I just wait for the final analysis - often an exhaust design issue.

Peter
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Old 19-02-2021, 06:59   #35
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Re: Do you have an exhaust out the midship side?

mvweebles this thread is about fumes only due to have read the other threads on the forum re exhaust engineering. Read and studied all the technical information available, working with local plus remote professional. What I could not find was anyone with practical experience with regards to fumes. And as a charter fumes its a major consideration to to go ahead with this recommendation.
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Old 19-02-2021, 07:05   #36
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Re: Do you have an exhaust out the midship side?

Long time ago I was part owner of a Morgan 41 OI. One of the first Catalina Morgans. Midship exhaust discharge. Anchored at night, calm, the exhaust would push the boat around in a circle.
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Old 19-02-2021, 07:46   #37
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Re: Do you have an exhaust out the midship side?

Quote:
Originally Posted by LakeSuperior View Post
A side exhaust for a generator is problematic for two reasons.

Wave slap can jet water through the exhaust hoses even with a loop up to the level of the deck. Remember that the exhaust hose run is short, half the width of the hull. The wave jet can eventually flood the exhaust system resulting in sea water in the cylinders via an open exhaust valve.

When the boat heels and rocks, excess sea water in the exhaust hoses and water lift can drain into the head.

The head and valves eventually corrode and fail. Hydraulic lock was not seen because an exhaust valve is only open on the up-stroke.

There is a exhaust exit fitting with a rubber flap having beveled sides that can be purchased to minimize the problem however we found that it may not make a perfect seal.

A side exhaust system needs to be well engineered to give trouble free use. Ask me how I know!
My generator side exhaust is not set up exactly that way. My generator is on the starboard side of my boat, the exhausts exits on the port side. We have a fifteen foot beam. There is a water lift muffler in between. It's been that way for 48 years without water ever getting to the engine.
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Old 19-02-2021, 08:15   #38
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Re: Do you have an exhaust out the midship side?

Quote:
Originally Posted by auspain View Post
mvweebles this thread is about fumes only due to have read the other threads on the forum re exhaust engineering. Read and studied all the technical information available, working with local plus remote professional. What I could not find was anyone with practical experience with regards to fumes. And as a charter fumes its a major consideration to to go ahead with this recommendation.
For Trawlers and such, 90% have generators. I'd guess 80%+ exit the side. I do not recall any complaints on a modern generator/install with gen-sep and below-water exhaust. But if you're swinging on an anchor or a mooring where you're always pointed upwind, having the exhaust mid-ships will increase chance of fumes to passengers. How much? With my little 6kw NL, near zero. An older 20kw Onan or something....could be a problem.

It's uncommon for side-exhaust is recommended on recreational-class vessels. Surprised you have two independent opinions recommending it. Sailboats have a fairly high incidence of exhaust screw-ups that damage their engine. If your engine manifold is at/below waterline, you are at-risk. If you are carrying extra weight at the stern such as passengers waiting to dive or disembark or similar, you are at-risk.

Peter
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Old 19-02-2021, 12:51   #39
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Re: Do you have an exhaust out the midship side?

As in a previous post, my exhaust is side-exit, below waterline. From the exit point (skin fitting), the exhaust pipe goes right up to against the underside of the deck then down to a waterlift in the engine room bilge and along floor level the the back of the motor where it again loops up vertically to the mixer elbow.

I believe there is zero chance of seawater making its way from the skin fitting to the engine. Well, it hasnít in the 14 years Iíve had the boat.
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Old 19-02-2021, 17:47   #40
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Re: Do you have an exhaust out the midship side?

mvweebles we will run a 35 KVA Cummins in the late afternoon and evening for filling cylinders and cooking. West Australia is a windy place, we do get maybe 3 months of nice low winds. Genset exhaust outlet will be 2 or 3 meters forward of salon portlight hatch opposite the galley and passengers will be mostly on deck at that time. Main engine will go with the North Sea design and not concerned with as will be underway. We are going to use a Gas-Water separator on the generator. To confirm do we exhaust the dry cooled exhaust gas bellow or above the waterline please? (from reading here I am believing bellow is the way to go?)
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Old 19-02-2021, 20:51   #41
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Re: Do you have an exhaust out the midship side?

Quote:
Originally Posted by auspain View Post
mvweebles we will run a 35 KVA Cummins in the late afternoon and evening for filling cylinders and cooking. West Australia is a windy place, we do get maybe 3 months of nice low winds. Genset exhaust outlet will be 2 or 3 meters forward of salon portlight hatch opposite the galley and passengers will be mostly on deck at that time. Main engine will go with the North Sea design and not concerned with as will be underway. We are going to use a Gas-Water separator on the generator. To confirm do we exhaust the dry cooled exhaust gas bellow or above the waterline please? (from reading here I am believing bellow is the way to go?)
Why would you separate the wet exhaust to wet and dry, then discharge the dry underwater?
Does not make sense

Purpose of separator is to have a whisper quiet dry exhaust with no water splashing.

Careful with back pressure if you tried to put the exhaust underwater
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Old 01-03-2021, 07:52   #42
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Re: Do you have an exhaust out the midship side?

Hi I have a 54' center cockpit both main engine and generator exhaust from the port midship (same thru hull) no smell in the cockpit even with the Bimini up and a hard dodger. CHeers
Courtney
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Old 01-03-2021, 08:29   #43
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Re: Do you have an exhaust out the midship side?

SeaLife, Endeavour Ketch 43 has the generator exhaust on the port side midships. We don't run the gen when heeling to port and the exhaust is under water.
The danger is when shutting the gen off and you suck in water.
We never had a problem
We also have a shutt off valve but never used that.
Also run the gen after sailing and heeling strongly to port, just to dry out the exhaust
Wolfgang
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Old 01-03-2021, 10:10   #44
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Re: Do you have an exhaust out the midship side?

On my vessel the exhaust was vented just below the water line and in front of the two rear cabins.

I very rarely had any complaints about diesel exhaust smell, however, when cruising I was mostly under sail. Further, if I was on engine, the reason was I was going mostly upwind in which case the wind carried the fumes backwards without any fumes reaching the rear cabins.
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Old 01-03-2021, 10:15   #45
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Re: Do you have an exhaust out the midship side?

Quote:
Originally Posted by LakeSuperior View Post
A side exhaust for a generator is problematic for two reasons.

Wave slap can jet water through the exhaust hoses even with a loop up to the level of the deck. Remember that the exhaust hose run is short, half the width of the hull. The wave jet can eventually flood the exhaust system resulting in sea water in the cylinders via an open exhaust valve.

When the boat heels and rocks, excess sea water in the exhaust hoses and water lift can drain into the head.

The head and valves eventually corrode and fail. Hydraulic lock was not seen because an exhaust valve is only open on the up-stroke.

There is a exhaust exit fitting with a rubber flap having beveled sides that can be purchased to minimize the problem however we found that it may not make a perfect seal.

A side exhaust system needs to be well engineered to give trouble free use. Ask me how I know!
While crossing the Pacific I learned the hard way this can happen. I am not 100% certain if the water entered my engine from the exhaust just as you describe or if it came up the raw water line. However, I most certainly had an oil pan full of saltwater when I approached Palau.

Fortunately I knew to test the engine oil level before running and had one more day before reaching Palau to drain the oil, and flush some older oil for a few minutes...drain again, then add fresh oil. I specifically traveled with 40 liters of oil aboard just in case this occurred.

I only add this problem once and we were in some pretty heavy waves. High enough I had water in the pilot house.
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