Merc used the VST tanks in 1995 on EFI's I believe. The problem you describe sounds exactly the same as I experienced myself with 1996 502 EFI's. My engine would run OK to a certain RPM and then sometimes shut off for an instant like total ignition shut off.

When the fuel flow is restricted in the VST screen it usually is not completely stopped, but rather just limited. Thus limited RPM operation.

First, there is a schrader valve in the front of the EFI system that is easily accesible to check electric fuel pump fuel pressure. This valve should have a cover on it and is easy to get to. Your test gauge should have a bleed hose and release to drain gas into a bottle instead of your bilge. You should get somewhere around 33-35 lbs fuel pressure at that check point with engine running. make sure to test at various higher RPM. Pressure should remain pretty stable through the RPM range..

The most common reason for low pressure at that point is a clogged VST screen. You can remove the screen and clean or install a new screen and keep the old one for a spare as I do. The removal of the VST tank is reasonably straight-forward. There are a couple of bolts at the rear of the engine that bolt the entire assembly on. When removing the two ( 2 ) fuel lines make sure to mark them for location as they look very similar and both will fit both locations. There is also electrical to disconnect.

When separating the VST tank take care. The assembly is sealed with O-rings. Sometimes a small amount of super glue will keep the used O rings in place for reassembly. This job is best done on a clean repair bench.

I solved the problem with clogged VST screens by installing RACOR 10 micron fuel filters before engine but after standard Merc fuel filters. I have not experienced any clogged VST screens in over 125 hrs running.

I hope this helps and is relevant to your application.

Good luck.

To those who replied I appreciate it. I wound up installing a gaffrig fuel pressure gauge perminattly in the dash. Right away I knew something was wrong because I only had at max 32 psi and the service manual says I should have 42. Upon trying it out in the water in noticed that Every time the engine would miss/die whatever you want to call it the fuel pressure was dropping to less tha 10 pounds. I though I had a bad fuel pump untill I blocked off the return line to the tank and the pressure pegged the 60 psi gauge. I replaced the Fuel pressure regulator with a new one and add a hardin adjustable cover. Problem solved!!! Good thing it wasnt the electric fuel pump it was $456. Compared to a total of about 120 for the regulator and the Hardin add on.

That's the quick and easy fix we like hearing about!!

jadento what part of maryland are you from?

Near fort Meade central between Baltimore and Washington