I've been meaning to make this for a while but finally got to it yesterday.
I Started with 2 mandrel bent stainless 90's (available on amazon, or summit etc) and 1 12" section of 3" Stainless tube (i had it in the shop, but also available at amazon or summit etc)
Oddly enough the mandrels were a Perfect fit even before any trimming so all I had to do was square the ends and weld them together.
Once welded I notched the tube for the downpipe and marked where it would go. Cut that out with a plasma and then used a die grinder to clean it up. This could also easily be done with a dremel.
For the downpipe I slash cut it and then put it in a vise to taper the end to hopefully avoid as much spray as possible.
Then it was welded up and test fit:
From there I cut some stainless flanges:
The original plan was to do it without any couplers, just bolt it on.
However once I started that process it's damn near impossible to get the screw holes aligned and the angles correct so I caved and just sliced the ends off and put couplers on.
I can't fit my boat in my shop and I was too lazy to drag a welder out into the driveway, otherwise I would have just put it together and tacked it on the boat to fit.
This picture is before cleanup and squaring etc. I decided to have to tubes extend into the factory exhaust as it's a tight fit and I think it will add some support and take some stress off the screw holes.
Now I just need to add a support to the swim deck mount and I'll be good to go! That will pull the angle up a bit, as it sits it's sagging a bit under it's own weight in the silicone couplers.
Added a mount to the swim deck this afternoon and cleaned everything up a bit.
Total cost ~100 + roughly 2 hours of my time.