With uneven compression if everything else is ok the engine should be able to fire, it may not run smoothly though.  When turning it over with the starter you will hear the an uneven sound when it hits the low cylinder.  Our 41 has one that is down, not that much, but still runs.

I am not a mechanic but I am not sure how low is too low, someone else will need to chime in on that.  

@timothy-kruger TY............

@johnny-reb With a 25 lb difference in compressions I highly suspect the head will have to come off. A test to decide weather it is valves or rings is to do the compression test again but with a generous squirt of oil on top of the piston, the oil will help seal the rings. If the compression remains low the problem is most likely a valve not sealing but a increase in compression will indicate a issue with the rings.

Tony

@anthony-williamson TY, I will give that a try....