You won't smell anything, thats whats tricky about it. With 700 hours that is about the time some of the fuel components start to deteriorate. I'm still betting on a fuel issue similar to what I described.

Have you serviced cooling systems? Are all engines running same temp? A slightly damaged impellor will still move enough water to cool properly , but will allow water to drain from engine when shut off , causing enough radiant heat to boil fuel in fuel rail (vapor lock). Fuel pressure will still be ok , but injectors will inj air. Next time it does this , bleed fuel rail at fitting and look for air. Good Luck!!!

im going with parasail.check the impeller on the engine that wont start.had a 2000 454 mpi cool fuel with the same problem.take the fuel/water separator off and fill it with fuel and see if it will start(when it is acting up).replacing the impeller fixed the problem

you changed all the tune up parts except the coil.i think sutphin30 may be right.at this point the coil would be the easiest&cheepest thing to change.

aquaforce,please let us know what the fix was when you get it right.i can learn from this.

Before the season started this year I also replace all the impellers and water circ pumps and so far all these parts seem to be doing well. We ran the boat hard in the Pirates of Lanier poker run and the temps were stable which I expected but of course good. During the last no start testing I did check fuel pressure again and spewed out fuel from the valve and no air was seen doing this but I did not bleed it all the way down to specifically check for air. This same starboard engine had the fuel pump replaced about 100 hrs ago.

So my take away here is to induce the no start which is not hard to do sitting on the trailer, then fully bleed down the rail to check for air.

TRASH: After I do this bleed down checking for air I will check, wot, for the flooded scenario.
Thanks all.

I am going to compare coil ohms and spark test with another engine to see if a coil could be the issue. When I searched here for these hot no starts I could not find a resolved example like mine so I know this will help someone sometime. There is a Formula boater in Ohio that had a no start like this and the dist ign module solved his symptom. I am leaning in this direction partly because I have seen this in the GM auto products over the years so it doesn't surprise me to find it in a boat. I did however have more data using my scanner in the auto world to corroborate information for some concrete data for making a call. So far I have not found a smoking gun and am looking for data streams, methods tests etc to find a smoking gun. I have a module coming that I am going to install and test. There is another signal that is generated from the ign mod which is used for inputs in the auto applications. I wonder if the 5v signal above 400 rpm is failing from the mod when it gets hot and therefore all the functions for start are there but no signal to the computer for above 400 rpm operation. This is the part that I think, till I find otherwise, is failing and why it is very intermittent and only when hot.

I will pass on my findings as i'm sure it will help someone. Besides ((((( I gotta go boating )))))))) ARGH!

Hope you are getting a Delco module and are using real heatsink paste under it vs insulating paste that come with most modules.

If the paste is clear don't use it.

Yes, I agree on the paste and quality parts. It is very possible that I could remove the module, clean everything well and re-paste and make it work. I have done this before on other stuff but since the module has been hot to the point of not working, as I think, I am not willing to keep going with it. Only new good stuff for the Formula.

I planned to test today but it is raining.......argh.

FIXED !!!!!

Boating and had many hot restarts with no problem.

So the scenario is this: The distributor ignition module screws were rusty which indicates moisture at the least or heat from a bad ground contact at the module. The module would always give spark and injector signals even when it would not start; that was confusing. The no start seems to be caused by the 5V reference dropping off which carries the 400+ rpm signal to the computer to begin the start sequence. The resistor in the module would get so hot it lost it's ability to maintain the 5 volts and so the computer never knew to start up. It seems that when this was happening the 5 V could be lost while the engine was running but not shut off because the computer had synced up with the primary trigger therefore stay running until shut off but not restart because the 400+ signal was gone. This is what made troubleshooting this thing so tricky. The primary trigger through the pickup and module never quit so there was always a signal which made the testers I use say it should run and run it did, just not start up again after the 5V was gone.

I used Artic Silver #5 for the thermal paste. Top line stuff used for computer heat sinks and should far exceed anything this module will need. The original white stuff was nearly none existent and probably more of why the module failed.