I'm with T Square check for spark when it is acting up, could even be a weak coil

on mine the cable wasnt fully broken, but had a crack.. when the engine was not moving it appeared okkay.. when it was starting, the movement in it made a not so good spark.. hence why it was difficult to find.. thay checked the computer, all was okkay etc.. but 50% of the time it didnt want to start.. before this would start within 2 seconds each time..

I also have been dealing with this on my 2005 5.0 MPI.

It is a pain to have a pretty new boat do this when fuel injection should help.....

It happened to me this Sunday, first time out this year, hopefully it is the (old) gas, which did not help matters....

Hey everyone, thanks for all the input, I talked to my dealer the next day and he felt that it was in fact a vapor lock. I have been out on really hot days three times since and when we go to sit somewhere to swim, I run the blower for a bit, let the engine idle for five minutes or so before shutting off and even opened up the engine cover just to air out. Not one bad start since. Yesterday we skied for over an hour but it was not so darn hot and I did not even do all the above and she started proper every time even after sitting off while we swam for 45 minutes. I will keep that experience in mind for those really hot days in the future and take appropriate actions as above. Thanks again for the input.

My volvo 5.0gxi will take a several cranks to start after it has sat a while after being run on a hot day. It never did it until I moved to MO/KS where we'd routinely boat on 95+ days. If it's in the 80's it always fires right up. But on really hot days it will crank a while to start after sitting and hour or so. I know a guy with a Merc 5.0mpi that does the same thing. IMO it has to be vapor lock since it never does it on cooler days. Now that I live in Illinois and 95 degree days are rare, it always fires right up.