I cannot answer your question regarding all 3 models because I don’t have all 3. I have an S-65 but it has a tank w/out the glass. I have a P-65 that does. Johnson was famous for using the same part on many models, so I would suspect the sight glass assembly might be the same. The part numbers for the P-65 and the A-65 sight glass are: 25-176 top cap; 25-177 base; 25-182 glass. So those being the smallest and largest engines (other than the V-65) and having the same part numbers would lead me to say the gauge is the same on all models. I don’t have an S series parts list.
I made new sight glass tubes using cast acrylic a number of years ago and they have not discolored like the originals which turned blue. You must use cast acrylic because it machines well. Extruded will gum up when cutting. It is 1/2" diameter and has a thick wall for durability. I did make a replacement for my Lockwood Chief but used 1/2". Lockwood’s were originally 7/16ths so I had to turn down the ends. If I didn’t tell you that, you would never see the difference. The picture of my P-65 is not good but you can see the gauge
