There are some concerns relative to the height of the waterline and the manifold. Also, what other equipment
you have plays into it. For instance, do you have a waterlift muffler
is th ABYC standards for exhaust. There are some pictures and explainations that should help you.
Also, if you click on my blog (in the signature) I built my own from parts
at the home store and posted some step-by-step details on how I did it. The one thing I would do different is use galvanized steel
. When I built it I was concerned about metal fume fever but since making mine I did some additional research
and found out the temperature needs to be much hotter than what we generate on boats.
Good luck and fair winds,