Guess the fiberglass acoustical liner was restricting the air flow. On my RD-18 the liner was totally deteriorated anyway so I just removed the remnants and reassembled the air box without it.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20
“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."
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