Have you had this motor since it was new, or did you buy it used. It may have been rebuilt since it was tagged to run higher octane.

Either way your cranking compression in psi is not a way to calculate  dynamic compression ratio. If there are no issues with the engine using oil or oil accumulation on the spark plugs and it does not smoke i would not assume that there is an issue. But a leakdown test will give you a better idea of what is going on if you were to investigate further. IMHO i would leave it alone  .Camshaft design can effect cranking psi, so i would adjust the timing and run the reccomended fuel. I think 10-15% difference between cylinders is within reason, someone feel free to correct me if i am wrong  

I have a 460 harman marine  motor. It runs pretty darn good . Part of my winter maintenance i checked the compression and It read from 115 to 130 . The motor plate says it requires 93 octane at 10 degrees timing . Which would lead me to believe that the motor was built with higher compression . The plugs are clean and with no oil and it doesnt smoke , so would that be the valves leaking ? I am hoping for that rather than a full rebuild since funds are tight . Thanks in advance guys.

If that cranking compression cylinder pressure is relatively the same with all cylinders then you're okay; 115 is 88% of 130 so that sounds great.  Incidentally, cranking compression tests should be performed with the engine warm and at wide open throttle.

Your engine sounds to be one of those that has the 7.7:1 compression ratio...it is simply  a low compression engine.  You have already answered your queston, as far as a rebuild goes: " i checked the compression and It read from 115 to 130. The plugs are clean and with no oil and it doesnt smoke ,"

Run it.

LO