Johnson Piston Serial# Not Found?!?

[Chrisravosa36]

1974 Johnson 50hp - I found this number on the bottom piston when i took it out, same as the top. When I looked it up it just showed 1 listing for ebay. Im looking to see if this is a standard piston or if it .30 over.

318900 - 2

Thanks!

 

[Faztbullet]

Mike it at the skirt.....

 

[Chrisravosa36]

Mike it at the skirt.....

Sorry, dont understand what you are saying?

 

[jbcurt00]

Use a Micrometer to measure the diameter of the piston at the piston skirt

 

[F_R]

What you are looking at is the casting number. That is, the casting as it came out of the mold. From there, the casting is machined to whatever finished size it is to become. I've never seen an oversize piston that wasn't stamped on the top with the oversize (.020 for a 20 over, etc). Not stamped? Ought to be a Standard. But of course, not hard to measure.

 

[Chrisravosa36]

What you are looking at is the casting number. That is, the casting as it came out of the mold. From there, the casting is machined to whatever finished size it is to become. I've never seen an oversize piston that wasn't stamped on the top with the oversize (.020 for a 20 over, etc). Not stamped? Ought to be a Standard. But of course, not hard to measure.

Its just stamped UP for both pistons, for up side. I accutally bought the standard rings, and after I ordered them I didnt even think about if I had oversized pistons! Il still go buy a micro and check!

 

[lmuss53]

You can check that with a dial caliper from harbor freight for a few bucks, you don't have to spend the extra for a mic.

 

[racerone]

???-----You fit the standard rings in the bore.-----If the have the proper gap it is NOT an oversize bore !