Nice find! "B6917" is most likely 1954. It's a Commodore B Decked Speedster.
I say 'most likely' because it's a bit of a guessing game for vintage Crestliner. The factory records are lost to the ages and most sleuth work is by crowdsource.
The now-archived registry has several B models in the serial range of B7xxx registered as both 1954 and 1955. Your 6917 is obviously earlier than the 7xxx's which speaks to the earlier date.
Additionally, the wooden gunnels were largely done by 1955 and relegated to options. (Oak splash guards were also optional, fwiw).
Also, having Larson on the corner caps and on the upper left of the decal speaks to the earlier of the two years -although both of those clues were transitional in 54-55.
1956 introduced a whole list of differences so it's definitely earlier than that.
1953 was badged as "Larson Watercraft". No "Crestliner" yet, so definitely later than that.
Ultimately, that leaves '54 and '55. If I were to wager, I'd put money on 1954.