Took my boat to the mechanic this weekend and they did a fuel pressure test. (I was in there for routine drive maintenance so they did not have time to dig into it further). Trusted shop on LOTO. I have 1 motor lagging about 200 RPMs when cruising so they started with a fuel pressure test since they were pressed for time. When the key was turned on the pressure when to 43psi and held, as soon as key was turned off the pressure dropped to 0 with in a couple of seconds. Any thoughts? they are thinking possible injector or fuel pressure regulator. Where would you start?

Wouldn't that be normal? The 525 runs off a mechanical fuel pump after being primed by an electric one.

It stays at 43 until key is turned OFF.
Does the pump continue to run with the key ON, or just a key seconds when key is first turned ON?

Could be bad regulator or injector. Need to pull the vacuum reference line and see if fuel is leaking past the diaphragm of the regulator. If not have to pull the fuel rail and inspect the injectors

Alldodge: just for a couple of seconds.

Pump runs a couple seconds and stays there, then when key is turned off it goes to zero
That's something I haven't heard before. There is no reason for it to do that, I'm stumped

in order to bleed off 43PSI of fuel, it has to go somewhere.

The test was performed with a proper mechanical fuel pressure gauge correct?... or did someone make a dash mount 12v into a test gauge (battery supply goes off, reads 0psi even though the pressure is in system)

Probably grabbing at straws with that... but even a bad injector bleeding off that much could/should/would wet out a cylinder

I was thinking the same thing, I read back though and he said it bleeds off after a couple of seconds. If it needed 12 volts and lost it, the needle should go down instantly

brand new mechanical snap on fuel gauge. I was standing there, It held pressure one time but the other 3-4 did not. we did not want to do it too many times and hydro lock the motor if it was an injector.

Voltage, applied to an injector or not, should not have anything to do with the injector loosing fuel. The ECM applies a ground to one leg of the injector to turn it ON (pulse). Removing 12V from one side without a ground being applied to the other side by the ECM should do nothing.

That said, turning power OFF does have an effect. So is it a bad injector issue of some sort, or an issue with the ECM. Keep in mind the fuel pump is not running

Is the correct method to test the ECM, injectors or other? Unsure if testing a MEFI-3 will be able to tell if it's applying a ground when power is removed for s split second before power leaves the injector.

Since RPM's were down from the beginning, I would lean toward testing the injectors