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Old 01-24-2020, 12:04 PM   #21
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Many sailboats, and your hull looks kind of like a sailboat, run their exhaust up inside the gunnel to get way up above the water line then back down again. Looks like you could get maybe 3' above the water line if you could do that.


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Old 01-24-2020, 12:40 PM   #22
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On my generator exhaust, the hose exits the waterlift muffler and goes up vertically through the floor to a loop. The hose from the loop goes back through the floor and slopes to the transom.

Having the top of the loop above the floor allowed for a greater slope to the transom outlet.

The loop is hidden with an enclosure.
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Old 01-24-2020, 01:09 PM   #23
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What about dumping it out the side? My generator dumps a few inches above waterline, 2/3 of the way forward on one side with a downward and aft facing clamshell over the output. Exhaust slopes down from the injection elbow to the muffler, up out of the lift muffler, then a fairly steep slope down to the discharge. It's worked well for years (and even self drains enough that it doesn't have a flooding risk during long cranking). The clamshell makes it fairly hard to push water back into the outlet.
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Old 01-31-2020, 09:14 PM   #24
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Centek makes great products, I've used them for years and routinely send my boat building clients to them for design assistance. Having said that, I'll echo the thoughts of others by expressing concern about exhaust check valves, primarily because there's no way to be sure they are working. I've removed a handful that were literally hollow, the guts had disintegrated. I would not want to rely on it. As an alternative, you might simply go with an external flap, at least that you can monitor.

This article covers a range of exhaust design details, you might find it helpful. https://stevedmarineconsulting.com/w...s170-FINAL.pdf

While you are refitting the exhaust, I would strongly recommend the addition of a wet exhaust temp alarm, they have saved many operators from damage and expensive repair bills when cooling water is lost.
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Old 01-31-2020, 09:44 PM   #25
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Quote:
Originally Posted by Steve DAntonio View Post
Centek makes great products, I've used them for years and routinely send my boat building clients to them for design assistance. Having said that, I'll echo the thoughts of others by expressing concern about exhaust check valves, primarily because there's no way to be sure they are working. I've removed a handful that were literally hollow, the guts had disintegrated. I would not want to rely on it. As an alternative, you might simply go with an external flap, at least that you can monitor.

This article covers a range of exhaust design details, you might find it helpful. https://stevedmarineconsulting.com/w...s170-FINAL.pdf

While you are refitting the exhaust, I would strongly recommend the addition of a wet exhaust temp alarm, they have saved many operators from damage and expensive repair bills when cooling water is lost.
First, thanks so much for taking the time to assist. Based on input from several others, I had abandoned the check valve idea and am working to understand how to get a better slope into my exhaust hose. Boat is in Ensenada and I'm in Florida right now, so need to wait for my next trip there in a few weeks

Second, your article talks about using a thermistor set at around 165 on the hose, just after the mixing elbow. Any guidance on sourcing this? Is this an off the shelf item?
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Old 01-31-2020, 11:27 PM   #26
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Someone may have suggested a thermister but that also needs a proper unit to read it.

Tony Athens strongly recommended the Airpax snap switches which will simply close setting off the simple alarm. You just have to chose the temp needed for it to close.

http://airpax.sensata.com/pdfs/5003.pdf

YOu can contact Seaboard Marine to buy them or chase them.

www.sbmar.com

If you go to Seaboard tell them what it is for. You should be able to find and read TOny's article about setting up the alarm.

Installed in the proper spot on the exhaust it will warn of a loss of raw water long before the coolant will tell you anything is wrong.
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Old 02-01-2020, 09:04 PM   #27
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Originally Posted by mvweebles View Post
First, thanks so much for taking the time to assist. Based on input from several others, I had abandoned the check valve idea and am working to understand how to get a better slope into my exhaust hose. Boat is in Ensenada and I'm in Florida right now, so need to wait for my next trip there in a few weeks

Second, your article talks about using a thermistor set at around 165 on the hose, just after the mixing elbow. Any guidance on sourcing this? Is this an off the shelf item?
Yes, it is an off the shelf system, affordable too. This article will give you a hint... https://stevedmarineconsulting.com/o...alarms-part-i/ Pay special attention to the photo captions.
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Old 02-02-2020, 04:41 PM   #28
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The exhaust hose alarm (just as shown in Steve's article) looks like a zap strap that goes around the exhaust hose right after the mixing elbow (water injection point). I know of 2 brands, Borel and Aqualarm (there could be more). I installed the Borel on my boat because it goes into alarm about 10 degrees earlier than the Aqualarm. For either, you will need the panel with audible alarm (it is loud) to mount near the helm. It will alarm with a buzzer and a warning light, and it can be muted. For a type of redundancy, I also installed an Aqualarm flow alarm that goes in the raw water hose between the sea strainer and the raw water pump. This one could save having to replace an impeller if you forget to open the strainer intake. These alarms cost in the ball park of $100 each, plus the panel (about another $100) so they are very well worth the expense.
My exhaust alarm was the only thing that warned me that my exhaust hose was overheating from a failing exhaust elbow. At all other locations (as verified by IR gun) the (engine) temperatures were great! This saved me from possible turbo or even engine damage.
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Old 02-03-2020, 02:06 PM   #29
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I have a similar but different make boat and I ran dry exhaust up to 18 inches above the waterline and looped it down to attach the water injection elbow. from there it's pretty standard with a Centek waterlift leading to a Vetus gooseneck at the stern (no transom, double ender). There's plenty of system volume to contain the backflow when shutting the engine down and plenty of height to ensure zero water gets even near the exhaust manifold. The dry portion is simply black pipe fittings with custom made exhaust blanket covering it, cheap and easily replaced. The pipe fitting at the manifold is a tee with a reducer on the down side and an all metallic drain valve to open when shut down to prevent any condensation or moisture getting into the engine.
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Old 02-04-2020, 01:52 PM   #30
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Exhaust System Design - Comments?

[QUOTE=mvweebles;840281]Attached is an original line drawing from a 1960's era brochure of the W36. Note how low the sole (red dashed line) is compared to the waterline - maybe 14-inches, and thus the issue of getting adequate slope.



At this point, I'm looking at lowering the outlet a bit, and will make a decision on the check valve at that point.



Thanks to all - the NL article was also helpful


Peter




Peter,
I thought I would pass on a modification a previous owner made to Hull No 34.
The sea water is injected at an elbow directly on the manifold, with a hose to a water lift aft of the Velvet Drive. The discharge from the water lift goes vertical to a 3 fabricated fiberglass goose neck pipe that penetrates the cabin sole vertically to a point about 16 above the water line, then back down to a horizontal run immediately below the sole. A hose then slopes gently down to a discharge just above the water line at a point about half way between the boarding door and the aft point of the stern.
The gooseneck blocks part of the door as it has to be located inboard of the water tank. The stbd door half is fixed, held on by screws and angle brackets so it can be removed to take something large in or out.
While we loose half the door, we gained a large cabinet with space for microwave and Kuerig, and extra storage. The cabinet is more useful than the double door.
The goal of course was to get the 16 drop from the high point of the exhaust pipe to the water line.
I will try to post some photos, my attempt to attach them to this post failed miserably!
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Old 02-04-2020, 02:07 PM   #31
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Exhaust System Design - Comments?

The photos, I hope:
Peters drawing with my configuration added.
As you can see the gooseneck gets the exhaust run up high enough that a check valve is not required.Click image for larger version

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Old 02-04-2020, 02:11 PM   #32
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The gooseneck protruding above the sole, and blocking the stbd half of the double door.
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Old 02-04-2020, 02:14 PM   #33
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The cabinet covering the gooseneck with space for microwave and Keurig coffee maker.Click image for larger version

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Old 02-04-2020, 03:10 PM   #34
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Originally Posted by Island Cessna View Post
The photos, I hope:
Peter’s drawing with my configuration added.
As you can see the gooseneck gets the exhaust run up high enough that a check valve is not required.Attachment 99033

That install is similar to the exhaust for my generator. The top of the loop on the exhaust is 16" above the cockpit floor in an enclosure.

And what I use for a loop is a Centek Gen Sep.
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Old 02-04-2020, 03:31 PM   #35
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I put a new exhaust system in Island Seeker when I first got her.
1) I had no problem going from manifold right down to a 45 degree side entrance waterlift mounted beside the shaft just ahead of the bulkhead. Thus nothing above the manifold to leak back into the engine nor expensive jacketed elbows.
2) Then straight up to under the deck and back to the transom.
3) I placed a gooseneck there, at the transom, about 12" high b/c I planned to be anchored in a seaway in the trades. Then out the original outlet.
4) for coastal cruising this gooseneck would not be necessary.
I never had a moment of trouble with this system over 9 years.
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Old 02-04-2020, 04:56 PM   #36
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The gooseneck protruding above the sole, and blocking the stbd half of the double door.
Attachment 99034
Thanks Bill - Looks like the type of modification that has a back-story to it. What engine does your W36 have? I didn't quite follow where your exhaust outlet through the hull is and how high off the waterline.

Attached is the graphic from the Steve D article showing proper exhaust installs based on engine placement relative to waterline. Bill - I'm thinking the W36 is the middle one - exhaust manifold is near waterline. Based on advice from my mechanic, I had an exhaust elbow fabricated that rises-up then makes a u-turn down where the water is mixed-in, more or less the bottom diagram in the attached. Not sure I needed to do that - was pretty expensive to have fabricated.

What I'm still a bit confused about is I would think the mixing elbow coming out of the engine should be the high-point of the system, not the loop coming off the lift muffler. If the 'wet/cool' loop is slightly lower, I would think the chance of back-filling the engine is greatly reduced. I certainly accept that ABYC states this is proper, I just don't understand why.

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Old 02-04-2020, 05:06 PM   #37
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Interestingly, on both my engines and generator the post-muffler loop is the high point. And I know my generator won't back-flood from extended cranking. It actually manages to push water out the exhaust during cranking.
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Old 02-04-2020, 08:32 PM   #38
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Thanks Bill - Looks like the type of modification that has a back-story to it. What engine does your W36 have? I didn't quite follow where your exhaust outlet through the hull is and how high off the waterline.


The engine is a Perkins 4-236. It was installed new in the late 90s, and is equipped with a full set of Murphy Switchgauges, so Id do suspect there is at least one back-story, but I have not heard it! Location of exhaust outlet and waterline in photo. I do not se any evidence of a past outlet on the stern centerline like most W36S have, so I assume this is the original location. BillClick image for larger version

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Old 02-05-2020, 06:18 AM   #39
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The engine is a Perkins 4-236. It was installed new in the late 90s, and is equipped with a full set of Murphy Switchgauges, so Id do suspect there is at least one back-story, but I have not heard it! Location of exhaust outlet and waterline in photo. I do not se any evidence of a past outlet on the stern centerline like most W36S have, so I assume this is the original location. BillAttachment 99039
Interesting. My 1970 W36 has a 1989 4.236 so something changed on my boat too. Most W36s had 6.354s in them, though there is a smattering of other engines including GMs and old Gray Marines (a GM variant). In my opinion, the 80hp 4.236 is perfectly matched to W36, though my preference would be a JD 4045NA, but not enough of a preference to repower.

But back to the exhaust, these boats were built from 1961 through 1970. I'm guessing the original exhaust systems were mostly galvanized pipe which probably had a hand in why our boats were repowered along the way.

My current plan is to lower the hull outlet to provide some slope aftward, though may not go as close to the waterline as your Island Seeker has. And I'll replace the rubber hose run with fiberglass as much as possible. I have always had a flap on my exhaust so will retain, of course. No other check valve or gooseneck.
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Old 02-05-2020, 08:33 AM   #40
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On boats with low exhaust outlets, I've installed the Vetus gooseneck with great results.

I've mixed Vetus Goosenecks with Centek mufflers and Gen Seps or used the Vetus mufflers.
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