Has anyone had any problems with brand new Merc VST electric pumps (808505T01)?

I had a pump taking a crap on me so I got a new one from a local marina on Friday. It was $700 ofcourse. So I drop it in Friday afternoon and it runs worse than the pump I took out of it. Swapped it with the pump form the second motor and the new pump is still worse than both old pumps. The motor will barely fire and idle and is clearly starved for fuel. So, I bring it back defective and get another brand new pump kit. I install it last night and it's the same sh!t!! This time I have my fuel pressure gauges and it's only putting out 15psi with the vacume regulator hooked up and about 20psi with the vacume disconnnected. I put the old pump back in it and it's reading 35psi. I check the second motor and it also reads about 35psi. So, I've recieved two brand new junk pumps directly from Merc?

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Are you taking PSI readings from both motors or just switching pumps out and taking readings from the initial side you thought was bad? Only reason I ask is cause you may have a power delivery problem on the weak side. Try voltage check on good side and see if bad side has same votage or near. Just a thought

Is the mechanical pump feeding the vst working properly?

I've checked both motors for fuel PSI and swapped out pumps on both motors. Here's how it all went down.

Starboard motor developed a stumble and narrowed it down to fuel delivery
Swapped origional VST pumps in starboard and port motors
Engine stumble moved to port motor after fuel pump swap
Installed new VST pump in port motor - replacing origional VST pump that the engine stumble just followed
Port engine would barely fire and hold an idle with brand new pump
Reinstalled origional VST pump and port engine would start and idle with no problems
Installed second brand new VST pump in port engine and engine again would barely fire and hold an idle
Verified with gauge that fuel rail was only about 15psi with brand new pump
Went to starbord motor and showed 35psi
Reinstalled origionial VST pump back on port engine and it showed 35psi exactly like starboard motor

Based on this the only logical option I can see is that both brand new pumps are junk. The sumble followed the fuel pump when I swapped them. Then when getting the new pumps both performed equally poor and the old VST pump performed better, matching the starboard VST pump. The only reason I am even changing the pump is because the stumble develops after running for a while and I think the one origional VST pump starts to fail after it gets heated.

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airtex makes those pumps for merc per my local merc rep and that says all I need to know lol. but yeas check your mechanical pump.

It's not the mechancial pump. I have litterally have had the old pump back in the motor twice now and it runs fine. For example....1st new pump runs like garbage....pop VST cover and put in old pump....10 minutes....motor runs fine for several minutes....pop cover put new pump in again....motor runs like garbage. This has also been verified with the PSI gauge.

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if post 5 is true about airtex making the pump for merc then i can back up the fact that the mfr of those pumps suck,,usually last a year in a car..try to cross the pump to a delco pump..also look at the fuel pressure regulator on the fuel rail..

Uhhhh. Why in the world would you spend $700 on a junk pump? You could almost buy 2 nice pumps wired and and ready to go for that kind of money...

Whats the part number bro?

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I feel for ya brother, I fought VST Bull Sh-t forever and finally ripped it all out, including the mechanical pumps.. ( Both motors) put in aeromotive pumps with regulators and by-pass and they purrrrrr like a well oiled kitten, not to mention my mid throttle punch is way better now.. My issue was due to vapor lock,,, tons of blogs on here about.. If you think about all involved with that VST system and the mech. pump on the water pump etc....Merc. Engineers must have been hitting the pipe that day... I went all out on my conversion and had Eddie Young do my rails,, cleaned injectors etc,, that said I had about $
1200 a motor with the new braided lines.. Wasn't hard to do either just time consuming ( maybe ) 5-1/2 hrs each.. Good luck.