Need Some Water Jacketed Exhaust Pipes

[Nubbs]

Question for y'all. Anybody ever make their own water jacketed exhaust pipes? I've got the IMCO Powerflow manifolds with the 90 degree riser. I need a water jacketed pipe from the riser to the transom. I'd like to build them myself as I don't want to mortgage the house for some pipes.
Thanks
Nubbs