In my case the metal fragments damaged the rear bearing supporting the drive shaft so much that the shaft was misaligned by belt tension enough that the H2O pump wear plate o-ring had a steady drip. The water leak was my hint that something was amiss with that assembly.

Your oil leak might mean something...

... or just need to be repaired.

My symptoms were: pull throttle to idle, a couple minutes of idle speed then stall, crank, stumble, stall, crack throttle(the hissing is the idle air control valve trying to make a really big air leak, this helps make a bigger one and gets the tps to increase injector duration to get some fuel for it to catch-that the vst pump is finding in short supply cause the vst tank is virtually empty), crank, fire, run in neutral approx 2500 revs, idle in gear for thirty or so seconds, stall, repeat crank procedure, put in gear and go home(about ten miles) at 4000 rpm. Ran fine while flushing on lift at 1200-1400 rpm, then stalled at idle speed after a couple of minutes. Then repair.

Appreciate everything, will tear into it today and see what comes out of it. Also if anyone else has any clues to this mystery, please let me know!!
My motor alway's ran perfect, I take very good care of my boat and it's contents. My engine never vapor locked before, I live where it's hot, the Miss. Gulf Coast, and lived in St. Petersburg Florida also where we bought the boat, ran in hot weather all of it's life and never once did anything like this till just recently. The boat is a 1992 Baja Outlaw in near perfect condition. The previous owner installed a new 502 Mag EFI crate engine into it in 95. I just want it back to it's old self again, I am sure yall understand!! Thanks alot,
Randy

If you can get a hold of a scanner that would help. You will see if it has thrown any codes. you can also leave it on there and run it, then be able to tell what the MAP sensor and TPS are reading when the problem occurs.

Last time I saw one of the combo raw water/ mechanical fuel pump leaking at the front seal like that, it was full of gas due to a failed diaphram. You might be on to something.

Dave

Hello Dave...If the diaphram was or say, is bad, would it still run part of the time like it does now? I mean it will crank right up right now and run perfectly and you can take off and get on plane and run. I have only noticed this problem when I come down off plane and slow down. Or sometimes it doesn't do it at all and when we get ready to leave later in the day after rafting off to other boats or spending the day at the islands, it'll start and when I get ready to take off and get up on plane, she stumbles right down and starts that spitting and sputering crap, then eventually dies. I need a code tester badly, I may end up having to bring it somewhere to have it repaired there. I am about tired of messing around with it. Keep the info comming guy's I check it regularly.
Randy

If you see oil leaking out at the mechanical fuel pump then the diaphragm has failed in the fuel pump and diluting the gear oil. I had this happen to me.

I also had the other problem that you have with a 502 EFI going dead after running a while and the motors sounded like they were starving for air. Made it real tough coming in a marina after running for a while. Anyway, I talked to an engine builder at the Sarasota offshore a few years ago. He told me that I more than likely had a carbon buildup on the pistons and it acts like charcoal and sucks up the fuel and creates a lean condition to the point of stalling. He told me to use Marvel mystery oil in my fuel and sure enough it corrected the problem. I tripled the dose in the beginning and then just continued to use it.

I am not sure if the diaphram failure would cause symptoms like yours or not. It's possible that due to lack of lubrication (gear lube diluted/washed away) the pump is overheating. Maybe check pump temp when symptoms occur.

Also, if you smear a little of the leakage from the pump on your finger and smell it, a strong smell of gas will confirm pump diaphram failure. Or just pull the fill plug on the pump (be careful it may be under pressure).

Dave

This type of problem may not generate a trouble code, but if you want to check for codes use the LED and paperclip trick.

Dave

im having this same exact issue with my 502 mag efi in my 1993 formula to the T. Did you ever find out what your problem was?

my 502 efi mag is doing the same exact thing right now. Did you ever find the problem? I put a cooler thermostat in mine so it runs in between 140-160 now so i wouldn’t think it’s a temp problem