Hot/dry exhaust installation
As far as the hot-dry exhaust, it''s dangerous, but you can do it if you do it right. First, it REALLY needs to be well wrapped with insulation, and I mean completely. I have done this with thick fiberglass tape for many customers, and have a sort of system that I like. I carefully wrap the entire system with one layer, then wrap over it with stainless steel safety wire. Then I completely wrap it again in the opposite direction and do the wire thing again. If I have gotten thick enough fiberglass and feel safe (I like at least 3/8" of thickness, and extra pads anywhere the system gets support. If the fiberglass isn''t thick enough, I keep wrapping until it is. It''s better to take the time and be safe than to have a fire break out just when you''re trying to make it through a difficult inlet in rough weather, and bad things always happen under the worst conditions. Last, I use that red High-temp gasket sealer and put dabs of it all over the glass on the seams, mashing it into the surface to help prevent the glass from migrating around due to expasion/contraction and vibration, but don''t try to seal it or it will hold in moisture and rot the pipe, and don''t try to make a hard skin by putting anything like resin on, because it''ll catch fire.
You can make a good solid exhaust out of plumbing iron pipe and secure it well, so long as you don''t transmit sound to the hull, but you have to use a section of about a foot to eighteen inches of flex pipe between the engine and the solidly mounted pipe to allow for engine mount flex. Wrap that the same as the rest of the pipe, but check it more because it flexes, and keep anything like fuel lines or electrics well away from it.
I know it sounds like I''m a know-it-all saying all this cautionary stuff to someone who probably knows it anyway, but nothing scares me more than propane except a dry exhaust. Last thought - fitting at the transom or hull needs to be insulated.