Other Rear Exhaust Size and Routing

[smokeysevin]

Currently preparing to do a rear exhaust conversion on my js550->750 swap and I need to know the proper tube size to run.

I am also looking for input on stainless vs aluminum vs fiberglass tube for the tube inside the tray. My primary concern is corrosion so I am leaning towards stainless or fiberglass.

Finally, do I need to run a "trap" in the tray walls to keep water from backing up or can I run a straight section of tube and run an inverted u-bend inside the hull?

I am still in the process of deciding on what type of sound suppression I will run. I like the square style waterboxes that the superjet guys run, seems to package nicely. I also like the cost and simplicity of running a resonator but I don't want to go deaf.

With a waterbox, it seems like I could get away with not running a trap but I don't want to lock the motor or suck water in while cranking.

Thanks,

Sean


Trap inside Tray:
Cleaner Install, takes up less space, more glass work required to fit trap into foam. I am not planning on doing any tray mods just yet.


Trap inside Bay
Messier inside engine bay, takes up more space in rear of compartment, easier install, no extra cutting required, just run hole saw front and back then punch foam out.

 

[smokeysevin]

Played around with some pvc today and it looks like 2-1/4" will fit with room to spare. I am considering using a 12" long stainless resonator for noise suppression with the option of adding a water nozzle to it.

Straight out of the stinger cone into a u bent up under the pole mount, back down into a 90 and straight into the resonator. Then out the back.

Input or opinions?

Sean

 

[Carrera911]

I haven't paid enough attention to 550 exhausts to know how they're laid out. But on superjets and probably most aftermarket hulls, its just a straight shot from the transom with it coming through the bulkhead just above the bondline. It then continues about 5 inches and ends up probably 3-4 inches above the bondline. I'm not sure about the scale of your drawing, but it doesn't look like the trap makes it above the bondline. If you could do a straight shot and end up with near the bondline, it should be fine with a baffled waterbox.

After 20 years and probably 10 of them being in a waterlogged tray my aluminum tube rotted through. Regular thin wall 304 stainless exhaust tubing and aluminum are probably about the same cost. 304 stainless should hold up better than aluminum, but 316 stainless won't be cheap. Waxing up some pvc pipe and making a fiberglass tube would be a cool option as well.

 

[smokeysevin]

Nothing is to scale but all that makes sense. I will plan to go that route.

Thanks for the sanity check.

Sean

 

[1970Camaro]

Reviving an old thread... did you complete the rear exhaust mod? I'm considering doing this to my yamaha swapped 550, was wondering which material you decided on and how it works? If so I'd like to see pics, please!