I did the job when I re-powered my 5.7 OMC. I thought the job was easy, but that was on a brand new motor. I used Sierra manifolds and risers. The fit and finish were excellent. Sierra paints them with an epoxy finish that is very tough. It has been 1 year and they still look brand new. I also used all new hardware that made installation easy.
I would much rather do the job on my boat than replace a set of V8 exhaust manifolds on a car.

BassOMaticII
On the left coast in search of Whales