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I am revising this C&C 27 Mk II's A4 exhaust. I found lots of info on sailboat specs and design in general, but would appreciate some specifics on the C&C 27. What layouts are used in this model with an Atomic 4?
This Mark II 27 has a 12" x 12" Onan water lift muffler. It seems solid enough, but I'll remove the bushings and inspect inside over the winter. It sits on a plywood base just to port of the aft end of the engine, against the bulkhead.
I'm probably going to design and have built a SS pipe run from the manifold to the muffler. I know I could use black steel from the hardware store, but I have access to a good welder.
On this boat, the muffler base is a few inches higher than the base of the engine. The manifold dry exhaust outlet is about level with the muffler inlet. Currently there is an 8" high loop in the 1-1/4" pipe from manifold to muffler. I plan to run a longer coolant hose from the manifold to the pipe, with an antisiphon valve at the top of the loop.
The current exhaust hose from muffler to transom is 1-1/2". It loops up the port bulkhead near the engine to the gunwale, then aft just under the toerail to loop midship at the transom and then down to the throughull outlet: 12.5 feet. Seems long to me. I'm wondering why I can't just go vertical from the muffler (I have 18") and then come along the inboard edge of the locker to angle down under the ignition panel and out more directly to the transom. That should cut off 4-5 feet, helping to reduce backpressure.
Any thoughts?
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"New" 1974 C&C 27 Mk II undergoing refit
Last edited by (2008-09-30 19:08:46)
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1974 Mark II C&C 27
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Hi.i am refiting myself my new mkIII 76 and i had to replace the ss pipe by a nother one i found at keate marine for 175$ but it is desing a bit diferent L shape so i ad to fit with couples niples . You can also look at vetus they carry a swan type wich is close to the original.I am sure you will find something that will fit your atomic four.For my consern it took me couples weeks before i found the rigth piece .hope that will help you. Good lok
From what I can tell on the Internet, it looks like the original A4 exhaust on these boats ran directly aft to the transom, which makes more sense. Perhaps they used a jacketed muffler that sloped down and directly aft?
I found the photos of Hyperion and Towser's systems for their diesels, and the stuff on Moyer's site, but I am interested in other ideas folks have about optimum design of A4 exhaust for this boat.
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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Towser's original exhaust used a waterlift muffler (a stainless coffee can with inlet and outlet on top) mounted on a plywood platform over the stuffing box. Exhaust hose ran from the water-injection elbow down to the inlet, then from the outlet through the under-cockpit bulkhead up in a loop into the space between the cockpit and transom and down to the stern outlet.
Since the hose was all under the cockpit, the lockers were clear and the exhaust hose was safe from chafe by locker junk. As most of the length was hose, there was little to resonate with exhaust noise. The hose didn't go very high into the transom, nor was there a siphon-break anywhere, which isn't ideal, but there was no indication water had ever been siphoned.
The diesel's exhaust, in addition to what can be seen in the photos, now includes a 180-degree elbow with siphon break on the exhaust line. This passes through a hole conveniently located high up in the plywood brace between the cockpit and transom.
David Weatherston
Towser, Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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David, I like that plan the best. MMI's waterlift is smaller and should fit in there well, allowing me to build a proper SS elbow that runs downhill to the waterlift from the manifold keeping everything midships with fewer bends and shorter runs, all of which seems to be the preferred design.
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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David, in that original setup, was the waterlift's inlet lower than the manifold outlet? Yesterday evening I studied the dimensions carefully on this boat, and I cannot picture a waterlift muffler in there over the stuffing box that allows for a downward sloping elbow. The hot (dry) exhaust pipe would have to loop up to the maximum allowed by the underside of the cockpit floor (about 6" vertical lift max) and then down to the muffler inlet. That's what the boat currently used: a pipe section with those dimensions leading to the muffler placed on the shelf to port of the aft of the engine, so I would not gain much. Fortunately the static waterline is below both the manifold outlet and the waterlift inlet.
There is surprisingly little about exhaust designs for this type of C&C on the Net. I would like to learn more about the original exhaust setup, and design options since then. I guess the good news might be that this boat design is fairly robust in terms of exhaust layouts, since there are few negative stories about it. There must be quite a few still running A4s.
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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Towser's A4 had a cast iron water injection elbow sufficiently tall that it had to be removed before the engine could come up off its mounting studs. From the elbow, there was a relatively small but obviously sufficient downward slope to the s/s waterlift cannister, which was perhaps 6 or 7 inches tall, excluding the inlet and outlet pipes.
There's nothing about these systems on the Web because, as you suggest, there aren't any (or many) negative stories to be told and so everyone simply takes them for granted.
David Weatherston
Towser, Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
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1. If anyone has a photo of a C&C 27 or similar with a waterlift muffler midships behind the engine over the stuffing box, I would like to see it. There is no sign that one had been placed there on this boat, and engineering a shelf for one would be a lot of work. Plus I don't want to block access to the stuffing box.
2, There is a small aluminum bracket that lightly screws to two asymmetrical wooden blocks GRP'd to the hull on either side of the stuffing box. The bracket extends down to surround the stuffing box, and the upper surface does not look like it ever played a role in support a waterlift. That bracket is a mystery too - I can't figure out its purpose.
3. The other mystery is the original purpose of the wooden shelf off to port of the aft of the engine that currently supports the waterlift. It looks like it was built into the hull, and has a hole in the center presumably to open the shelf under the base of the waterlift. If it was a battery shelft, it would not have a hole there. Is it possible this Mark II originally had a waterlift there?
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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Here is the muffler shelf. Do you think this the original design for the 1970s Mark II? <a href="http://www.flickr.com/photos/penguinfun/2958084438/">http://www.flickr.com/photos/penguinfun/2958084438/</a>
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"New" 1974 C&C 27 Mk II undergoing refit
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1974 Mark II C&C 27
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