Exhaust System is a Go!

Finally, after seven weeks of worry, googling and angst, we have our repaired exhaust riser installed in Galapagos.  Here is what we finally ended up with.

Exhaust riser 3.0. Now with more wiggle. Since this photo was taken, I have added an additional brace in the vertical plane.

You will note an eerie similarity to the first riser we had built in Astoria. The only difference is that we have added an eight inch long 2.5 inch wide flexible coupling as close to the exhuast manifold as was possible. The flexible coupling is a bellows type with a smooth liner inside to protect the bellows from exhaust particulates which hopefully will prolong its life.  I opted for a larger flex coupling in the hopes that it will provide some additional strength to the whole unit.  Sizing the coupling up came at the expense of requiring two stainless cones to fit the coupling to the existing pipe.

New Coupling with cones

New Coupling with cones

All of this is a departure from an earlier design that would have increased the diameter of the exhaust to 2 inches right after the manifold and added a flex coupling horizontally instead of vertically. I still like that idea and may design another system using threaded pipe to allow me to build yet another exhaust riser if this proves unreliable.

The design Steve Hulsizer and I came up with. I like the fact that it is sized up to two inches. The flex coupling would have to be fairly small (4 inches long?) to fit in the space available.

So why didn’t I just have the new riser designed like this? Mostly I was talked out of it by the welders who tended to agree that the existing design was actually quite robust in all areas and the only modification needed was the flex coupling to allow for engine movement without stressing the riser.  The existing system is quite beefy and at this point I can only hope they are right. Still I would like to have a new manifold flange made with a 1.5 inch NPT fitting welded on that would allow me to create my own riser using easily acquired stainless fittings and pipe. Broomfields, the local exhaust experts in the Puget Sound,  has a flex coupling with NPT fittings welded on that would be ideal for such a project.

As you may note, I am not done worrying over this part of our engine. Maybe it will just take some time with this layout to begin to feel that this is a safe and robust system. On Saturday, I added an additional brace to the riser and used what fiber glass heat tape I had left to wrap the majority of the pipe. I ran the engine for an hour at a variety of RPMs and everything looked great. In reality the engine moves very little except at dead idle. At 750 RPM, you can see the coupling moving perhaps a quarter of an inch. Since I know the engine moves most in this range, I tend to bump the speed up a bit as soon as I can and the vibration disappears quickly. Still, boats tend to spend a lot of time at idle, especially during docking maneuvers. When docking, I prefer to worry about crashing into expensive boats and would rather not have to split my time worrying over the engine.

Wrapped, braced and tested. I’m not sure how to wrap the flex coupling or if I even should.

Now that we have a functoning engine again, Let’s hope the weather will allow us to get out on the water a few more times. We are well and fully into fall here but we should have a few days here and there that will allow us enjoy a crisp autumn sail.


25 thoughts on “Exhaust System is a Go!

  1. John Wanamaker Nice job. If you want to wrap the flex section use an “exhaust blanket” it wraps around the exhaust then has a wire and clip system to attach back onto itself. I would recommend this as the flange is at the hottest part of the system.
    Like · Reply · 38 minutes ago

  2. YEAH!!! Finally OMG. I bet you two are so happy to finally have a working solution while the weather is still “warm enough” to sail. hooray! Now get out there and work your Dark whale magic. 🙂 We need pics!

  3. Michael, you definitely should insulate all the way. The thermocouple on my engine has shown over 900 deg F on a full power run. If you have the misfortune to have a fuel leak spray on the pipe, you will have a fire. I still have a scar on my hand from a fuel leak from 52 years ago. Holland America lost one of its sail ships (I was the port engineer for that ship) due to fuel leak, a total constructive loss, not sinking.

    The set up does look nice, though. Shame to cover it.


    • Thanks Steve and I intend to fully insulate the riser. I recalled that you had gotten insulation from EJ Bartells? As it turns out, their office is about a block away from my office in Renton. I’ll call them tomorrow and see if I can pickup something that can be wrapped around the flex fitting that will allow movement with wearing or chafing. I’ll do some research on that tonight.

  4. Excellent, the PVC, template? Had 5 bends, your as-built has only 3, and a flex pipe is an excellent vibration dampener. Your engine will breathe easier!, and thanks you!

  5. Do not wrap the flex pipe, it dissipates it’s own heat.
    The lagging your using could be a lot better, if your interested Dunato’s Marine can hook you up with a pro to make these for you, they will snap on and look and perform amazing. Ask to talk to Ryan Hansen.

    • Thanks Shawn. It sounds like you are referring to a pipe clamp that could place anywhere along the length of the riser? I have a couple of other attachment points that are welded directly to the riser that I can use. I need to pick up some angle iron to make those work though.

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