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Thread: Decoding numbers on OMC heads.
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04-02-2002, 09:44 AM #15000 RPM
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Decoding numbers on OMC heads.
I have a very early eighties 175 hp Johnson. The heads that are on it have this number: 325-557. I have some heads laying around that are obviously higher compression and they would fit that block. The numbers on these are: 323-457. Can someone please tell me by the numbers what the differences are before I bolt them on. Also, what kind of performance gain could I expect if any. Thanks