1963 75hp Pistons are Different

[yorab]

I've just purchased .020 OS pistons for my 1963 Evinrude 75hp rebuild project. After inspecting them, I noticed that one piston is different from the others. I understand that different manufacturers may have differences in the casting, but there are two differences in the final machining. It is different in two ways. First, there are small, parallel grooves machined in the outside circumference of one of the pistons from the top down to about the wrist pin hole. The other difference is that this piston has a much larger machined area on the top surface. Are these differences critical? Can I use that piston with the others? The pics are on Flikr:

http://www.flickr.com/photos/jmm741/sets/72157622360009043/

 

[F_R]

Re: 1963 75hp Pistons are Different

I've just purchased .020 OS pistons for my 1963 Evinrude 75hp rebuild project. After inspecting them, I noticed that one piston is different from the others. I understand that different manufacturers may have differences in the casting, but there are two differences in the final machining. It is different in two ways. First, there are small, parallel grooves machined in the outside circumference of one of the pistons from the top down to about the wrist pin hole. The other difference is that this piston has a much larger machined area on the top surface. Are these differences critical? Can I use that piston with the others? The pics are on Flikr:

http://www.flickr.com/photos/jmm741/sets/72157622360009043/

I have seen both types. Personally, I wouldn't hesitate to mix them.

 

[yorab]

Re: 1963 75hp Pistons are Different

Thanks, FR