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DaleH

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Up to about 1970, Johnson OB model numbers were two or three letters and a two digit number coding. Motors after 1960 of the 'RD' series were based on a 43.9 cu-in. block. The 'S' may be a production run code, useful for ordering parts. Guessing that the 'L' may be for long shaft, but this is all I can find.

Looks like we need Pappy to chime in here for the absolute answer ...

OldOB2.jpg

OldOB.jpg
 
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