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.