1969 Chris Craft Roamer 46 Refit: New Exhaust Risers II

DATELINE: Far side of planet earth (finally getting over jet lag, just in time to return stateside and start over).

While working on the engine wiring, there were several times when the project got stalled because I didn’t have the right hardware to get ‘er done. Since I can only work on the boat on weekends, a week can go by waiting for new parts to show up so I can continue the job. There are plenty of other things to do on the boat, though, and getting the exhaust system finished is a big item on the honey-do list. I’ve got all the tubing I need. I just need to finish preparing the mufflers, then cut, tack, and weld the risers together.

Stainless crush sleeves get bonded to the muffler inlets and outlets

In retrospect, I may have been able to save several hundreds of dollars by buying a 5-foot length of 6″ stainless tubing and cutting it to size rather than buying Centek crush sleeves at $58/ea (wholesale). Ah well…that wouldn’t be the first time I made a noob choice that cost more than it had to.

ta

High temp epoxy thickened with glass bubbles and cabosil bonds sleeve to the muffler

ta

Smooth the epoxy and clamp the sleeve in place

ta

Rubber pads on the bottom to isolate vibrations

I still haven’t decided for sure how much I want to isolate the mufflers so they don’t transmit exhaust vibrations. Since they’re not solidly attached to the engines, vibration may not be a problem at all. Time will tell.

ta

Muffler gets placed on its platform

Starboard muffler loosely positioned

Starboard muffler loosely positioned

The 180° connector above the muffler allows it to be rotated and also moved in a small arc to line the inlet up with where the riser will be.

Next, figure out how to connect the turbo flange to the muffler

Next, figure out how to connect the turbo flange to tubing pointed at the muffler

Cutting somewhere around here ought to do it

Cutting somewhere around here ought to do it

And then another one up here should wrap it up

And then another one up here should wrap it up

Harbor Freight bandsaw cuts pretty straight when its adjusted right

Harbor Freight bandsaw cuts pretty straight when its adjusted right

I had a problem with slightly crooked cuts on the stainless tubing I used for the fuel inlets, which took more work on the disk sander to get the mating surfaces fitting tightly. With the bigger 4-inch tubing I’m using on the exhaust, it was even more of a priority to make sure the cuts were all true. I followed online instructions for truing 4×6 metal-cutting bandsaws, and it cuts nice and straight now.

Touch up on the ShopSmith disk sander

Square up the cuts on the ShopSmith disk sander

Good fit

Pretty good fit…just a bit more and it’ll be perfect

Looks about right

Looks about right

Ready to tack

Position is marked with a Sharpie…ready to tack

Thick flange and thin tubing are a bit more challenging to tack than similar materials

Mahogany cleats position the tubing perfectly

Mahogany cleats position the tubing perfectly

The muffler inlets are ~6″ in diameter. By clamping two 1″ x 1″ x 24″ mahogany cleats to the inside of the inlets, the distance between the two inner surfaces of the cleats is ~4″. By clamping the 4″ tubing to the other end of the cleats, I can position the mandrel-bent section while being confident that the other end is pointed directly at the center of the muffler inlet. When I weld on the showerhead, which will be made of 6″ tubing, it will be pointed right at the muffler. That’s the theory, anyway.

More tubing cuts

More tubing cuts

Touch up the cuts for a perfect fit

Touch up the cuts for a perfect fit

Saw marks = gaps

Bandsaw blade marks on the cut = gaps where the tubing will butt together

Saw marks = gaps

After a bit more sanding, no saw marks = no gaps

Nice and flat, with no gaps

Nice and flat, with no gaps

Tack this bit to that bit...

Tack this bit to that bit…

Add a bit here across the top

Add a bit here across the top

Double-check the angle down to the muffler

Double-check the angle down to the muffler

Note that the “spillover point” on the dry exhaust side is well above the lowest point of the 180° connector coming out of the muffler. That way, if the exhaust system fills with water it will naturally drain out the side of the hull rather than backing up into the engine. The 6″ exhaust pipe out the hull side would have to be completely full and still overflowing under substantial pressure before water can end up in the turbo. Gravity makes that pretty much impossible.

Tack in place

The final piece of tubing is tacked in place

Ready for final welding!

Ready for final welding!

The dry side of the port exhaust riser is ready to be welded, but I’m still awaiting the delivery of some gear to purge air from inside the tube and replace it with argon. I also have to make the dry section of the starboard riser and have some parts CNC machined for the showerhead.

Next up on our 1969 Chris Craft Roamer 46 Refit: New Exhaust Risers III

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8 comments on “1969 Chris Craft Roamer 46 Refit: New Exhaust Risers II

  1. VIctor says:

    Howdy from Florida, if you spray high temp ceramic paint on the inside of your exhaust pipes, will some of the heat mitigate foward and out thus helping somewhat with high metal temperatures, I can say from experience that a injected water restriction will melt the centa waterlift ……food for thought

    • 1969roamer46 says:

      Hi Victor.
      You’re right that hoses and fiberglass can only take so much heat. But a wet exhaust failure is more of a testament to poor system design than poor material choices, isn’t it? I won’t be using ceramic paint inside stainess tubes because paint is paint, and none of it lasts long at 900°. Showerhead design is also critical. Lots of them dump too much water out onto the bottom of the hose at low temps, completely failing to act like a proper showerhead and lower the temp of the exhaust gas. I’ll be covering that issue soon, and hopefully my approach will work better than what you experienced.
      Cheers
      Q

      • My Info says:

        Even the best wet exhaust system can have failure if A..your intake strainer gets clogged B..your reduced seacock gets clogged C.. your seacock gets shut and stays shut when you turn back on D.. you get a kink in your intake hose E..your intake hose clamp pops off F..your water pump impelef rots off .G your raw water pump head preassure blows its clamp and fills your bildge with water , and the list goes on and on… it happends fast and it happends underway, and you end up with super heated exhaust ,,,, any hoo I know the motercycle shop down the road sprays hi temp paint on the inside exhaust pipes, he claims it prevents the chrome from turning blue and keeps them cooler, … what about welding cooling fins all along the dry exhaust side?

        • 1969roamer46 says:

          Hi. I won’t be painting the inside of my exhaust system. As for cooling fins outside, since the exhaust system is inside the boat and the heat tends to radiate into the engine room unless the system is properly insulated, heat sink fins would make it harder to get the heat off the boat ASAP. The approach I’ll use is to insulate the outside of the dry section, which keeps all that energy in the tubing until it’s doused at the showerhead and then routed off the boat.
          Cheers,
          Q

  2. Kent says:

    Nice–

  3. Chooses to be anonymous says:

    use some of the spiffy D.E.I. exhaust wrap tape on the riser instead of one of the bulky standard heat sheilds and maybe even get a turbo blanket

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