2004 6.2 MPI bravo engine with fuel problems

[chs marine service]

this motor has no serial #, no flame arrestor cover. that being said, the engine takes a nose dive when going full throttle the pressure tested confirms the fuel pressure drops to 10PSI . i know its the pump, but the issue is, i hve not seen this set up before, it has 3 pumps, 1 on the engine bay wall( fuel delievery ?) then 1 bellow the alternator, no case, just sitting there in line (low pressure?) then the fun one, under the port side of the engine ( high pressure)
most of the engines i have dealt with only have the delivery and the high pressure. this is my 1st
6.2 is this standard on the 6.2's?

just to say, i know the HP pump needs to be changed, im just asking about the design

 

[alldodge]

First no Merc original installed motor has 3 pumps
The 6.2 is no different then a 5.7 other then a longer stroke

Taking a dive at WOT I would look at the antisiphon valve or other restriction feeding the pumps. Only other thong is one of the pumps cannot keep up

 

[Fun Times]

Sometimes a fuel filter may get mounted along the engine bay wall as this engine model/year range looks to had used a filter there, a low fuel psi pump mounted around the fuel filter area/bellow the alternator and then a high psi pump under the motor mount to the port side.
Items # 14 & 27,
https://www.mercruiserparts.com/bam/.../31955/8093/80 and https://www.mercruiserparts.com/bam/.../31955/8093/60

If it's anything else, maybe posting some photos may help jog a memory or 2.

 

[chs marine service]

yes fun times, those are the pumps that this system has, i need to look again but i was certain that the 3rd pump i was talking about was a delivery pump but more posts i read, i am startgin the think it in fact may be a metal case fuel filter.
i have worked on many earlier MPI's and they have a delivery pump mounted on the front wall of the engine bay which then feeds the seperater filter, then the cool fuel II pump.

 

[Fun Times]

yes fun times, those are the pumps that this system has, i need to look again but i was certain that the 3rd pump i was talking about was a delivery pump but more posts i read, i am startgin the think it in fact may be a metal case fuel filter.
i have worked on many earlier MPI's and they have a delivery pump mounted on the front wall of the engine bay which then feeds the seperater filter, then the cool fuel II pump.

Yes some boat dealers and boat manufacturers have put a fuel pump along the engine bay wall to help with some other known performance situations that arose of only using the High psi pump...Things like vapor lock, low fuel flow to the high pump to name a few.

Often the screen in front of the filter or pump (what's ever there in your case) could get blocked up with debris causing fuel all of a sudden low fuel psi situations at high RPM then go back to more normal at low RPM.

We often would take a 5 gallon gas can with a new fuel line hose connected in place of the boats fuel line and run the boat to see if fuel psi dropped in-turn bypassing the boat side of the fuel system...Also try using a fuel pump primer bulb to add more (and sometimes feel) fuel pressure differences.

Maybe someone added a pump along the wall not seeing the other one mounted to the engine already from new...Or something...