Mariner 200 EFI fuel pressure issue?

[Ricky_rich]

I have a problem with my Mariner 200 EFI. It loses fuel pressure to the injectors sometimes. I have installed a gauge so I can keep track on the value. And I have now connected an electric fuel pump between the tank in the boat and directly into the VST tank. It gives 97 gp/h liters/min if needed. Was out driving a few days ago and after about 20 minutes the pressure suddenly dropped below 29 psi, the engine stops immediately. Otherwise it is at 35-38psi, moves a little when I press the throttle. Tried another gas tank earlier this summer, but no difference. Have also changed the fuel pump to the injection, no difference there either. Could it be the fuel pressure regulator that is causing the problem? But pressure goes up to 37 and stays there when I turn on the ignition.
I have also done the voltage test on the pump as in the "voltage test chart" below, and all is good. I have plans to connect a voltage meter to the pump and monitor the voltage while driving. (as in test no.6)

 

[dingbat]

Had the exact same symptoms/issue on a motor a couple of months ago.

Keep looking (hoping) to find another (cheaper) problem in the system but knew from experience that it was a failing HP fuel pump.

Got tired of dealing with the issue and spent the $300 for a pump. Installed the new HP pump and the problem went away

 

[Ricky_rich]

Had the exact same symptoms/issue on a motor a couple of months ago.

Keep looking (hoping) to find another (cheaper) problem in the system but knew from experience that it was a failing HP fuel pump.

Got tired of dealing with the issue and spent the $300 for a pump. Installed the new HP pump and the problem went away

Did change the HP pump earlier, not cheap, but made no difference.
Difficult when the problem only shows up now and then. I have noticed that I have 2.9V on pump - side when running over 2000rpm. Should be below 2V according to manual. But I have 2.9V both when engine running good and bad.

 

[Dukedog]

Should be below 2V according to manual. But I have 2.9V both when engine running good and bad.

this would lean towards a ecu pump driver problem.. disconnect tha pump from tha ecu power.. both positive and negative... hook tha pump up to any purple (switched hot) on positive and ground on motor.. this by passes tha ecu.. pump will run anytime key is on....

 

[Ricky_rich]

this would lean towards a ecu pump driver problem.. disconnect tha pump from tha ecu power.. both positive and negative... hook tha pump up to any purple (switched hot) on positive and ground on motor.. this by passes tha ecu.. pump will run anytime key is on....

Thanks for the tip, I will give that a try to rule out the pump driver.
I believe you have some knowledge about these engines. I made a video last time I was out on the lake. Can you take a look at it, listen to the sound of the engine? To me it's not running on all 6. I have gone through all the injecors and they are all working.