A friend of mine who is an infrequent visitor here, asked that I post here in the tech section a problem he ishaving with one of his 502mag's. The motor sit's in a 1991 40' Super Hawaii one of only approx. 13 made. Below is his email to a few of his friends asking for suggestions.

"I can get it up to about 2300 RPM's before it breaks down and losses power and behavs like a John Deere tractor. If I slow down below 2000 it perks up again, but craps out if increased to approx. 2300rpm. Intermittently it will continue fine above 2300 but eventually craps out again and repeats the symtoms.
I changed the water separator in the beginning thinking simple fix. BTW both motors work off the same tank, and the other motor continues to run fine.
The problem continues to come & go. I have swapped the following from the bad to the good motor with no change in either: New Cap, rotor, plugs, plug wires. Moved the ignition coil, computer, distributor, fuel & ignition relays. What else should I be looking at???

Update:
Found #1 cylinder injector with no pulse. Pulled #3 (same side) flashes fine. I was told the injectors are grounded in banks not individually? and others should also be down?? then I ran out of daylight to go further. Anybody know where I trace the injector wire/s? It must be to/from the computer, but
I'm looking for some guidance or other suggestions of what to check/look for???.....Thanks, John A."

his motor is doing what mine did . i chased it for quite some time and drained the fuel etc... really really acted like bad fuel... turned out to be one bad injector shorted to ground. found it by removing all the injectors and pulse testing them w/ the scanner... replaced that one injector and all probs solved instantly. symptoms sound identical to what mine were.

the pulse function on the scanner is wonderful.... set up a can w/ injector cleaner and a pump rig and pulsed them all forwards and backwards and got the spray patterns perfect again and made a huge dif in both power and economy.

Any examples (pictures/details) of what this can & pump rig gizmo is, and how to use it?

This may or may not help, but the injectors are pulsed in banks, one bank being 1,2,4,7 and the other 2,3,5,8.

Has he checked the fuel pressure?

Dave

I had a bad injector take a fresh motor apart this spring. Sent them to Marrem Fule injection (injector.com) nad had them clean and test them all. The guy was real easy to work with....cost $10 each to have them gone through with new O rings etc.