502 dies at wot
 

ok this is going on year 2..... boat dies at wide open throttle and if I pull the gas back she'll stay running. This is what i have done so far: complete tune up kit, rebuilt the VST, removed the anti syphone check valve, removed the screen in the pick up in the tank, changed the water seperator 20 times no water in it by the way, replaced all the vacuum lines going to the VST. Last thing for me to do is remove the drain plug and go for a ride and anchor somewhere.

Exactly what engine a and fuel system? I assume you are checking the fuel pressure?

checking that today... i did notice that the water sep didnt fill back up after i drained it and cranked the f out of it. the 3 hours later just leaving it alone it filled

1995 502 efi

fill the filter with new fuel if you dump it, that way it wont take as long to prime, you said dies ?? does it start stumbleing like its running out of fuel, I dont know the VST system that well but my old 502 mag mpi did something similar and it was a weak cool fuel pump.

it just cuts right off

hope its not the high pressure pump cause i really dont wanna spend a grand on a new one

dude I just went through this on my 502 if you have the mechanical fuel pump mounted to the sea strainer its probably the culprit if you have a cool fuel check your low pressure pump. mine has the old style mechanical pump on the sea pump. at idle it would carry 6.5 lbs as soon as you got on plane it would drop to bout 1.5 and did fine unless you were at WOT then would just poof die. so check the low pressure pump either way.

thanks... yes i have the same set up

Sounds like a fuel supply issue. All suggestions above are right on, also install a fuel pressure gauge even if its temporary. Hopefully it's a bad mechanical pump. I replaced both of my mechanical pumps last year because previous owner never changed the oil in the little "tank" and the pumps were starting to get wear on the arms due to the thinned out oil. I put in Merc pumps and had 1 bad out of the box, 1.5 lbs.! Replaced it again and back running fine.