Offshoreonly.com - 502 not starting

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If the water sep fuel filter had been changed, I would say yes, since it could have filled with water again.
Since it was not changed, then I'd say no. Something in the ignition is probably going bad and displays the problem when it gets hot.
I'd lean toward the dist pickup module going bad or possibly coil.

Quote:

Originally Posted by BUP (Post 4631504)

one needs to differentiate is the issue fuel side or ignition or sensor side. If one is going to work and attempt to fix their apps properly - good tools are needed and all the proper service manuals. .

Odds would say to me without the testing factor the issue is NUMBER 8 in the link below. Buy the Merc one not sierra..

. MerCruiser 502 Mag. MPI Bravo (Gen. VI) GM 502 V-8 Distributor & Ignition Components Parts

OP had the exact same issue with a brand new '99 5.7L EFI and it was ignition module. Boat would run like a champ for 20 - 30 minutes then boom, dead. You could let it cool off for 30 minutes then it would fire up and run fine again for another 5 minutes or so then die again. Boat only had about 10 hours on it when it did it so they can be bad regardless of age/hours.

Quote:

Originally Posted by SB (Post 4631511)

You've run into more issues with the magnetic pick up vs the electronic module in the EST distributor? Interesting. I have totally different experiences. We are on fresh water if that matters.

Hey SB -- the est for the 454 and 502 --- I was not comparing failure rates between the pick up coil vs the ignition sensor assembly. Keep in mind the 502 and 454 OEM stock used the est ign set up inwhich used the pick up coil internally.