I have acquired a number of form 337 field approvals allowing the total elimination of any type of air filter element. Instead I make a heavy duty mesh screen (1/8" wire) to keep the big things like birds out of the carburetor. The filter elements are to prevent dust from getting into the small carburetor ports and cylinders rings. If you don't expose your seaplane to dusty lakes then you really don't need a filter.
The first commercially operated floatplane I removed the filter element from was about 5 engines ago and every engine made TBO with normal compression and power. I don't know anyone who has ever used an air filter element in a float Beaver. I'm sure some people do I just don't know any of them.
Klaus Marx - Piper Pacer Pilot
Juneau, AK & Wenatchee, WA . . . . . . Click on Link Bar to view the 'non-profit' group.