fixing to blow up a boat!
 

What's the issue? The issue is the motor is a 502 Magnum EFI and the boat cranks idles for 15 sec then dies. It even dies when
you have it idled up to 3000 rpms with 15 sec.
here's what I've done so far:
Since the boat has 2 motors the port motor runs fine off of the same fuel tank
I have swapped over the vst, the coil, ignition module, and I've added an
electric fuel pump because I thought the mechanical pump took a dump.
Still the same thing.... shuts off after 15 sec.
I've also checked for codes and there are no codes. I mean WTF?!
The motor has recently been rebuilt and it ran fine during the break in period and
now it will not run for 15 sec. but when I tried to check the timing on it the boat wouldn't
idle in safe mode.
Any suggestions? i'm all ears!

Do you know if its losing fuel or spark???? That is the first thing you need to determine.

try swapping the dist .bet you find thats the issue

I don't know if its losing spark or not.... but the funny thing is..... is it will fire right back up
and the shut off again.

will it stay running if you run the starter and once you let go of the key it dies?

it starts up fine runs like normal and after 15-18 sec. it dies

sounds like its in the cool fuel tank..check the relay in the box..also make sure their is no blown fuse's under the plastic cap fuse protecrors...

also check the connection at the back of the ignition switch's and the connections at the safety teathers..

I had same problem on 454 may with merc aux vapor lock fuel pump added. It would burn fuel out filter then stop. Fuel was still coming out a little and you can turn the key to check it. I had my 5 yr old daughter turn key
while I tested , then a few taps and it started pouring out and working again.. cool fuel couldn't pull fuel thru the aux pump. Easy fix for me or I could have replaced the pump if it was actually out.

So it sounds like fuel to me.. check flow! Good luck

Yeah it's not a vapor lock issue and the boat doesn't have the cool fuel system. We've fixed we fixed the vapor lock issue with returns lines back to the tank. The fuel seems to be flowing good and when it shut off the last time I checked the vst tank and it was half full. This happens even with the first crank up of the day after sitting all night. It's almost like it runs up until the ECM goes through it's routine then shuts the motor down.

I wasn't referring to vapor lock but that kit. Mine would run till it ran half the fuel out of the fuel/water separator filter then quit.

I haven't checked the fuel water separator yet i'll go do that now and see where it's at

Yeah.... the fuel and water separator is completely full.... just checked it

I agree with smokin' gun
try swapping the dist or the module. You could also rig up a meter to the wires on the VST pump, or just jumper it directly to the battery to test. Just need to start isolating and figuring out what isn't working. If you think the problem is with the ECM, try swapping that also. Hope you get it figured out!

Hook a timing light up to any of the plug wires...1 is ok .....See if when the motor dies the light goes out ....that will tell you definatly whether it is fire or not ....You could also have a fuel pressure gauge attached on same test and watch results ...it's ez

Obviously check for water in fuel

thank you to everyone! I think i have fixed the problem. the boat has 2 water/fuel separators on each motor....why? i have no idea.
I bypassed the Racor water/fuel separator and connected directly to the one on the motor and it ran fine. I just think that trying to run
a 4-7 psi fuel pump through 2 water/fuel separators might just be a little to much.

I had my 5 yr old daughter turn key.

Did she fix the boat? Pretty cool to your kids by your side when working on the boat

dought its the problem .been running like that till now and the other motor runs fine and its set up the same way

She likes to play around in the cuddy usually while i am tinkering. My 8 yr old boy would rather stay inside playing, but not her.. dirt is her middle name. Usually, she just take my tools and plays with them then i am like wtf, where did it go!! Lol

Thinking they are like 6.2s. When you key on the pumps go on for 10-15 seconds then shut off if the do not detect oil pressue. There is a switch on the right side rear of a 6.2, its not the sending unit just tells the ECM there is oil pressure. That might be bad if your engines have it. A quick fuel pressure test will tell if they are in fact shutting off.