compression at 75 psi both cylinders

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rpijan

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I just tested my johnsno 9.9s compression and it is at 75 and 76 psi on both cylinders. I tested the motor cold (as I had other stuff to fix) and with the tester in one cylinder while the plug in the second cylinder removed. Is this the correct testing procedure? Is this psi a definite indication of my internals being severely worn? I can't justify putting too much money into this motor, but I already did just rebuild the fuel pump, am putting new plugs in, and have a water pump impellar kit on the way so I would like to use it. I think the motor runs ok, but it's hard for me to tell since I've had multiple problems at the same time lately.

I think I could afford to do the rings and any gaskets associated with that job, and I think I'd also be capable but I haven't done anything like this on and outboard before. I've rebuild small go-ped 2 stroke motors but they are quite a bit simpler I think. Who's done a re-ring and how difficult was it? Is it a bad idea to tear the motor down that far and not replace lower end bearings? it's a 74 johnson 10r74g
 
it goes like this:
pull both plugs
pull the starter cord, three of four times. check the compression, now do the same for the other cylinder. do this three times for each hole.
now squirt some 2 stroke oil and do the same, numbers should be close.
a 10% variance is fine.
70 pounds is about normal for a older motor, need to know year and if its a pull or electric start
dino
 
1974 and it is pull start

I tried two different compression testers and got pretty much identical numbers too
 
One thing that people commonly forget about when doing compression checks is the throttle position. Open the throttle wide open during compression test. If the cylinder can't get any air in it because the throttle it closed, it's got nothing to compress.
 

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