Asked the folks at BDS about the k&n's and they told me that all the filters are now cg approved, I think got the approval in Jan or Feb this year? From what I can recall on the dates.

I've stacked a bunch of standard Merc F/A's on top of each other before.

The little "normal" 330 sized arrestor. Those are give-aways from the local boat hop up shop. They have no use for them.

Cut the top out with a nibbler, leaving enough rim to poprivet it to the bottom of the one you'll put on top of it. Cut the bottom out of the next one the same way and put a bead of 4200 black on the rim and sandwich em together and poprivet them. The 4200 is just to keep them from rattling - silicone will melt after a while from the gasoline - use 4200.

I made two QUAD stacks of these for a bud running dual carbs. He liked the look. Still running them.

They seem to work very well.

And they re "made from" USCG approved pieces.

Eddie Marine and some of the K&N's are specifically USCG Approved, containing a designation stamped in the housing, or on the filter/arrestor itself. If it's not there, USCG will write the citation and basically end your day of boating. That's typically one of the first things they check every time I've been stopped.