Marine: Boating, Sailing, PWC, GPS and Navigation - Motor pops once or twice sometimes but won't start

Our Motor on the 1999 Triton (Johnson 150 ) (J150PLEES ) will not start. we have done a lot of work on it. (replaced a piston rod rings in one cylinder). Starting out the spring it was sometimes hard to start cold and has gotten steadily harder to start. Now we cannot start it but it still pops once in a while while cranking . I'm sure that if it were to start once it would start all day but after leaving it overnight last night it will not start. Also all spring starting the first time on any given day has been mostly hard to start

Thanks,
Nate

I would start with a compression check just to make sure the top end is fine. The next place I would look is at the primer when starting turn the red knob on the primer that will open it up then turn it back as soon as it starts.