Intermittent No Start

Hello Everyone.  This is a great post.  Lot's of great info on here.  I have a question.  I have a 1995 SN GT40 Pro Boss with a weird issue.  When I recently bougt the boat, it would have an extended crank when cold, but once it started all was good.  Once it was warm, it ran and started well.  Then the other day I took it to the lake and it all of a sudden had a weird crank, start immediately, run for one second then shut off issue.  It would do this over and over.  This probem cropped up simply by towing it to the lake (so I am assuming the vibration/bouncing on the trailer made something electronic unhappy).  I have replaced the ignition switch, bypassed the lanyard switch, replaced both relays, swapped the ECU for a known good one, checked engine grounds, verified battery voltage, voltage at the ignition switch, and voltage at pin 30 of the fuel pump relay lead.  All test good.  My boat does not have the 50 amp fuse in the battery box, fyi.  As I have been going through the testing procedures over the past few weeks, I have noticed different symptoms.  Sometimes I have intermittent power to the fuel pump relay, other times its dead.  The new relays I bought have a power light on top of them.  With the key on, engine off. the relay for the ECU has a strong consistent 12v signal.  The relay that controls the fuel pump  and spark will flicker and as it is flickering, you can hear the fuel pumps intermittently priming and the coil firing inside the distributor.  Then after it does this intermittent routine, it will loose power and all is dead again.  When the fuel pump relay is flickering, it will start, run poorly with an uneven idle, and then shut itself off.  On a few occassions while cranking, I have noticed the engine will fight the starter briefly giving the cranking event a brief stall, then will start cranking again normally, like an engine that has the ignition timimng off.  This is leading me to belief that I might have a PIP issue, if the sensor is feeding the computer bad data as to where the engine is running or not.  Any ideas?  Anyone else have this ame issue?  I would think that since I have a good consistent 12 source at pin 30 with KOEO with the relay removed, and also have a good consistent 12v signal to pin 87(or whichever one gets power from the relay - i can't remember), then the inline diode to the starter solenoid should be good, right?  Let me know what y'all think.  Thanks in advance for any input you might have