I've never read the regulations, just derived what I figured were the rules from two comments on page 273 of the WM catalogue:
"Clear plastic see-thru bowl is for outboard installations only"
and
"See-thru bowls allow easy visual inspection for water; metal bowls are recommended for use in areas of high heat and are required by the U..S. Coast Guard on gas inboards."
Plus reading betweeen the lines, looking at all the products, and thinkin' about it.
Joe.
"Clear plastic see-thru bowl is for outboard installations only"
and
"See-thru bowls allow easy visual inspection for water; metal bowls are recommended for use in areas of high heat and are required by the U..S. Coast Guard on gas inboards."
Plus reading betweeen the lines, looking at all the products, and thinkin' about it.
Joe.