Most leakdown test machines will have the allowable input pressure range marked on them.

Tip: Make sure that the cylinder being tested is absolutely right on TDC, and that you remove whatever tool you are using to turn the engine over before applying pressure. If you fail to do both, well.... :eek:

Compression test numbers?
 

I know the rule of thumb is within 10% range, but what sort of LB's should it be?

What's a fresh 500HP #'s?
When did you rebuild your 500HP #'s?

If they are 150 LB's, I assume that is good.
100 LB's bad...I assume.

So what numbers are exceptable? and what numbers are, on the fence of "refresh" (knock down the selling price of the boat numbers)