I am running 525 scs. Just received the boat on Sat and it ran great Sat and Sunday. I went to go out Tues and started having problems. Motor started initially and then stalled when we where leaving the dock. I was able to restart with much difficulty and return to the dock. It started with much difficulty but would not stay running. Did not spit or sputter, just would not start. I am now unable to restart. Heres what I have eliminated so far.
New plugs, because I fouled the old ones trying to start.
New distibutor sensor.
Swapped distributor caps, rotors, amplifier(?), coils, and the new sensor, just to be sure.
New fuel seperator, did not appear to be any water in it.
Checked front float, no hole.
I am getting fuel to the carb (pulled line and pumped fuel into can), and am getting fuel when I pump the throttle, I also have 8# of pressure according to the gauge.
Electric fuel pump is brand new.
That said I am not sure what I am overlooking.
I have put a charge on the battery as I ran it down trying to start it.

Other motor fires up on first try. Engines have about 300 hours on it and where recently serviced.
Any suggestions ideas would be greatly appreciated

Does it have a choke is it open all the way

No chokes.

Are you sure you are getting spark to plugs,

Weak spark with the battery low on charge.

Has to be electrical are you sure distributor did not move clamp not tight?

Clamps tight. Rotor is spinning. No misifiring. Seems to be spark related to me, but not sure what to check now.

After turning it over for about 15 sec or so pull a plug. It will be wet if you are getting fuel into cylinder. They probalby are. If plugs were firing at all it'd sputter some.
Does all cylinders sound even compression when turning over? I agree it sounds electrical/ignition related.

I did pull 1 plug, it appears to be getting fuel. Its not spittering or sputtering at all, although that would be exciting.

You have checked everything that I would have checked.
I would check the wiring harness that plugs into the ignition module for corrosion. Also make sure the ground for the module and module and module case are good.
I had a similar issue with my 525SC and it was the coil.
I would agree that it is most likely ignition related.
Do you have 1 kill switch or 2???

I had a few times when mine got flooded and was hard start. Try holding the throttle at WFO when trying to start it.