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1972 Evinrude 25HP Piston job.

J

jmhorsley14

Member
Hey guys, I finally got around to pressure testing the cylinders on my engine. The top one has 90lb and the bottom has 30lb so I assume I need new piston rings... what all is involved and what type of rings do I need to do this myself?

Edit: the model number is 25252r
 
You need to take it apart before buying any parts. If the cylinders are scored you will need oversize pistons and rings and have the cylinders bored. What condition is the gearbox and the parts needed to rebuild the powerhead you want to consider before making a decision.
 
If you need to rebore you would first need a set of pistons.-----Not sure where you would find those.-----------Flea-Bay maybe.
 
Make sure you know what you are doing when purchasing pistons. For instance,the 25hp are different than the 18-20hp, but look the same. You can not mix and match.
 
Okay. Well I have to get my hands on a manual first off. Then take it apart and figure out the parts needed? I looked at a parts diagram and saw two different types of rings for this motor, I have no clue what the difference is. Any ideas for when I get that far?
 
Ring design was a work in progress back then. 3-rings, 2-rings, pressure-back rings, etc. You have to put some reliance on parts books and superseded numbers. And history.
 
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