Exhaust System Design - Comments?

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.

The gooseneck protruding above the sole, and blocking the stbd half of the double door.

The cabinet covering the gooseneck with space for microwave and Keurig coffee maker.

Island Cessna said:

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.View attachment 99033

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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.

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.

Island Cessna said:

The gooseneck protruding above the sole, and blocking the stbd half of the double door.
View attachment 99034

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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.

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.

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.

mvweebles said:

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.

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The engine is a Perkins 4-236. It was installed new in the late ‘90’s, and is equipped with a full set of Murphy Switchgauges, so I’d 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. Bill

Island Cessna said:

The engine is a Perkins 4-236. It was installed new in the late ‘90’s, and is equipped with a full set of Murphy Switchgauges, so I’d 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. BillView attachment 99039

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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.

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.

I am quite sure mine (The Grey Goose) was fitted with a 4-236 ab-initio. It has a unique drive system with a custom thrust bearing/drip less shaft seal designed for the original owner, a cardan shaft and very soft motor mounts as well.
I also owned hull No 6, which was unfortunately lost in a disastrous boathouse fire in 2012. It had what I consider the best engine for the hull, which was the Gray Marine conversion of a Continental HD277 engine. This engine made 50 hp @ 2000 rpm, (intermittent rating of 60@2000) had a sophisticated 2 shaft balancer, a heavy (about 3” thick) flywheel, and special precombustion chambers to smooth the cylinder pressured (or so the advert said!). The package with a velvet drive as supplied from Gray Marine weighed 1450 pounds! That was a sweet engine, and I believe was specified by Bill Garden in the original plans. Unfortunately Continental quit making the base engine in about 1963, hence I assume the change to Perkins. This change was fortuitous for us as Perkins parts and service are fully available 50+ years later, Continental not so much!
I have no idea why they used so many 6-354’s in this hull, the 4 is more than adequate. Perhaps the smoother running of the 6. Bill

syjos said:

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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This is the perfect setup for the W36S. The gooseneck will fit perfectly in the tiller compartment under the cockpit seat!

Bill

Island Cessna said:

This is the perfect setup for the W36S. The gooseneck will fit perfectly in the tiller compartment under the cockpit seat!

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I looked at these - there is indeed a very good place to install one on a Willard 36 that would get the exhaust well above the waterline (and the cabin sole). But it would only be a high-point just inside the hull. Obviously, it would keep water out, but would also keep water in. On the engine-side of this high-point is 8-10 feet of 3"D hose plus the muffler lift muffler. I'm struggling to understand how that's a good thing. It's an honest question - I just don't understand. Maybe it's only a problem if the engine is over-cranked and I shouldn't worry. But it just seems like having so much of the exhaust system where water can collect just doesn't seem like a good idea. What am I missing?

Peter

mvweebles said:

I looked at these - there is indeed a very good place to install one on a Willard 36 that would get the exhaust well above the waterline (and the cabin sole). But it would only be a high-point just inside the hull. Obviously, it would keep water out, but would also keep water in. On the engine-side of this high-point is 8-10 feet of 3"D hose plus the muffler lift muffler. I'm struggling to understand how that's a good thing. It's an honest question - I just don't understand. Maybe it's only a problem if the engine is over-cranked and I shouldn't worry. But it just seems like having so much of the exhaust system where water can collect just doesn't seem like a good idea. What am I missing?



Peter

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I think the only practical answer to overcranking might be... don’t over crank. My gooseneck directly above the water lift has the minimum amount of water to run back to the water lift, but still would fill up to the manifold if cranking speed did not generate enough exhaust flow to lift the water clear of the water lift.

By the way, the Vetus gooseneck would fit nicely where my custom one is, and probably be more effective.

To protect against the overcrank concern you can always add a drain valve to the muffler. Then if you get a no-start, you can just drain the system before another attempt.

https://www.sbmar.com/category/articles/exhaust-systems/

I have shown above a link to Tony Athens' articles about marine exhaust systems. This is just the start. Take a serious look at his articles and examples.

He is strongly of the opinion that the highest point in the system should be immediately AFTER the turbo, NOT after the waterlift muffler. The cooling exhaust shower head should be just after the highest point downturn so even should that shower head leak the water cannot go back to the engine.

THis setup will not allow the engine to be flooded even if the waterlift is filled.



I strongly suggest you Read his articles, study them.

C lectric said:

https://www.sbmar.com/category/articles/exhaust-systems/

I have shown above a link to Tony Athens' articles about marine exhaust systems. This is just the start. Take a serious look at his articles and examples.

He is strongly of the opinion that the highest point in the system should be immediately AFTER the turbo, NOT after the waterlift muffler. The cooling exhaust shower head should be just after the highest point downturn so even should that shower head leak the water cannot go back to the engine.

THis setup will not allow the engine to be flooded even if the waterlift is filled.



I strongly suggest you Read his articles, study them.

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I haven't read everything, but this makes sense to me. I noticed in one of the diagrams that the lift muffler is actually raises up so that waterline is roughly midway up the muffler.

I really appreciate this. I'll read when I'm at a PC. I'll likely reach out to them as well.

Peter.

There is no requirement that, after leaving the waterlift that the hose travels downhill at all (mine is nearly level under the sole then turns up & down 12" at the transom in a gooseneck)

The purpose of the gooseneck is to prevent dipping up water in the outlet while hobby horsing at anchor, rolling it down the hose, filling the waterlift and eventually the engine. Flaps and check valves are not reliable enough to prevent this long term.



As long at the waterlift is large enough to hold any water that may be in the hose when the engine is shut down, it need not run out the outlet.


Sorry to chime in again on this but I have put a trouble free system in the exact same vessel...

Brooksie said:

There is no requirement that, after leaving the waterlift that the hose travels downhill at all (mine is nearly level under the sole then turns up & down 12" at the transom in a gooseneck)

The purpose of the gooseneck is to prevent dipping up water in the outlet while hobby horsing at anchor, rolling it down the hose, filling the waterlift and eventually the engine. Flaps and check valves are not reliable enough to prevent this long term.



As long at the waterlift is large enough to hold any water that may be in the hose when the engine is shut down, it need not run out the outlet.


Sorry to chime in again on this but I have put a trouble free system in the exact same vessel...

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Brooksie - I don't disagree, I'm just confused. There's a piece of me that says that if the second loop (after the muffler) is lower than the exhaust/mixing loop, there is no way it can back up onto the engine anyway. Not sure that's possible on the W36.

I'll get some measurements on the boat (will ping the Willard owners to see if anyone is on/near their boat as I'm 3000 miles away from mine). I'd like to ping the Tony guy cited by a previous post. Seems pretty sharp too. And get a feel for ABYC. Both he and Steve D cite those standards. Finally, have to figure out what physical constraints there are such as very low deck.

Thanks all - though in still confused, has been helpful.

Peter

mvweebles said:

Brooksie - I don't disagree, I'm just confused. There's a piece of me that says that if the second loop (after the muffler) is lower than the exhaust/mixing loop, there is no way it can back up onto the engine anyway. Not sure that's possible on the W36.

I'll get some measurements on the boat (will ping the Willard owners to see if anyone is on/near their boat as I'm 3000 miles away from mine). I'd like to ping the Tony guy cited by a previous post. Seems pretty sharp too. And get a feel for ABYC. Both he and Steve D cite those standards. Finally, have to figure out what physical constraints there are such as very low deck.

Thanks all - though in still confused, has been helpful.

Peter

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Peter,
I'm quite sure that all the sedans, like yours and mine, measure the same except that there have been different discharge openings depending on engine. On mine, where the hose ran under the aft deck, it could connect directly with the outlet, a straight shot with a little down slope. And all would have been well while running and at dockside.
But anchored in a seaway, water would have been picked up and rolled down the hose eventually filling the waterlift and then the engine. I did not want to rely on flaps or check valves to prevent this, thus the 12" gooseneck right b/4 the outlet.

C lectric said:

https://www.sbmar.com/category/articles/exhaust-systems/

I have shown above a link to Tony Athens' articles about marine exhaust systems. This is just the start. Take a serious look at his articles and examples.

He is strongly of the opinion that the highest point in the system should be immediately AFTER the turbo, NOT after the waterlift muffler. The cooling exhaust shower head should be just after the highest point downturn so even should that shower head leak the water cannot go back to the engine.

THis setup will not allow the engine to be flooded even if the waterlift is filled.



I strongly suggest you Read his articles, study them.

Click to expand...

That's referred to as a dry, as opposed to "jacketed" (example shown on page 61 of this article https://stevedmarineconsulting.com/wp-content/uploads/2014/03/ExhaustSystems170-FINAL.pdf), riser and unless the vessel design doesn't allow it, the case on some express cruisers, I agree, it is by far the preferred approach. Its drawback is you have a fairly large, dry section of exhaust in the engine room, which can produce a considerable amount of heat. It must be properly insulated (two examples shown on page 65 of the same article) to ensure its surface does not exceed 200F, preferably lower, at WOT. The third diagram down on page 63 also depicts a dry riser.

I've seen jacketed risers corrode, and leak water into the turbo, and through open exhaust valves, into cylinders, and seize engines.

I marked our exhaust path on the attached (probably clearer if you double-tap) and am curious if it’s considered inherently safe or unsafe. The outlets are several inches above the waterline with full tanks and the highest point—after the water lift—is about 2 ft above the WL. The elbow is at or below the waterline and there are siphon breaks on the raw water injection hoses. Are there cases of systems like this back-flooding?

I was at the Vancouver Boat Show yesterday and saw one of these: https://www.vetus.com/en/exhaust-systems/waterlock-muffler.html .

Certainly a way to put a high loop in the tiller compartment to avoid sloshing back from discharge without worrying whether the water lift could hold any drain-back from the long horizontal run of hose under cockpit deck. Bill

Island Cessna said:

I was at the Vancouver Boat Show yesterday and saw one of these: https://www.vetus.com/en/exhaust-systems/waterlock-muffler.html .

Certainly a way to put a high loop in the tiller compartment to avoid sloshing back from discharge without worrying whether the water lift could hold any drain-back from the long horizontal run of hose under cockpit deck. Bill

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UPDATE - I reached out to "Ask Steve" in the Q&A section of Steve D's website. His recommendation carries caveats, but best he can tell, his recommendation was to install the gooseneck at the stern of the boat as the other TF/Willard 36 owners have suggested (Island Cessna & Brooksie). Below is his verbatim message: