Baffling hic-up first time out today

That was a long read and I remember following along guess that gives Joe some tests to start with.
And again no final response/fix from the OP but I assume it was his ECM.

Well there ya go.
All I remember is when I was having fuel supply issues with my ‘95 it was necessary to jump the pumps to bleed the rail when it wouldn’t start after shutting off for a period of time when hot/normal operating temp. He could be running into that issue .

The relays still have to be in but the pumps will run continuously and if I remember right
(which may be wrong) is that bypasses the relay pump wise.

Symptoms sound like my old 96 gt 40. i replaced relays and the problem went away. Hope yours is as simple.

My '96 sport had a similar symptoms and I finally found the short piece of fuel line within the canister had a split about 3/8" long.
I am no heavy hitter on the site and often rely upon the wisdom of others but I would give strong consideration to a fuel delivery issue

LOL..... Well Ken, short of driving around in circles with a bunch of equipment and hoping it will happen again I was hoping one of the big brains on the site might have some insight first. Did I mention the water was really cold?
I do agree with the hot electrical possibility and had already thought perhaps the HP fuel pump but figured this was a good place to start since I was back home anyway.
I'll maybe have some time toward the end of the week to give it a test run.   Or circle in this case

   Got out for the first time today and all was going great for a couple hours. Drove all over the lake to test the boat and survey the lake for debris, etc with no issues - all within perfect specs. Stopped the boat to relax for a bit and take a dip in the still too cold water and then decided we''d better be getting back to the dock since weather was supposed to be coming in in the next couple of hours.

   About half way back the engine suddenly cut out, sputtered a couple of times and died. Cranking several different times and checking all the breakers I could not ascertain what the problem could be. At first the engine would sputter once every time I tried to start it but then just continue to crank, like either no fuel or no spark. Just before it died, all readings were normal - volts, temp and oil - and the engine wasn't hot to the touch.
Unbelievably, we were able to flag down one of the only 2 other boats on the lake and get a tow back to the dock. On the trailer at dry-off I tried once again and of course still no luck.

   Here's the baffling part .... about an hour or so later, finally back at the house I decided to try it one last time before putting her away and she started right up. No hint of a problem. Everything still normal, no sputtering, no rough idle. Just smooth and responsive.

Hmmm.... any guesses??   I can't diagnose a problem that now does not exist so maybe someone here has a thought or perhaps something like this has come up before?

-- For those that don't know my history, this is a 95' SN GT-40.   i.e. no fuel cell.
Engine was a new long block last year and most of the parts around it are new as well.
The only things not replaced at this point is the water circulation pump, fresh water pump, throttle body and high pressure fuel pump.