Low pressure Fuel Problem 2stroke Z200TXRZ

[Sailmaster]

Having trouble with fuel pressure on low pressure side.
Tested pressure and big drops to very low at speeds over 2000 RPM
Replaced low pressure fuel Pumps and gaskets. Yamaha Parts through boats.net
Same problem
Checked fuel feed system with vacuum gauge. Less than 3" vacuum
Same problem
Ran on known remote tank hooked directly to fuel filter intake on engine filter
Same problem.
Messed around with old removed pumps and found one could be blown through in both directions
Checked new fuel pumps and neither one holds 4 PSI vacuum
one pump actually allows air to be blown through very slightly. Removed that one and replaced with the one that holds a bit of vacuum
Ran at 4000 RPM for 3 minutes All is Good

Let engine idle to cool for 10 minutes and the pressure is now under 35 and drops with any throttle increase
Same problem

PXMKG515D101 YAMA 200 6G6 X 104618 Z200TXRZ 03/01

Attached to a Parker Pilothouse we use as a signal boat for sailboat races

[rodbolt17]

there are 3 fuel systems on that motor.
low pressure feeds fuel to the VST at about 68 PSI
medium pressure is the electric pump with a filter on it in the VST that feeds the high pressure pump at a CONSTANT 50 PSI.
high pressure is the belt driven pump that runs at about 625 PSI at ALL rpms.

[99yam40]

there are 3 fuel systems on that motor.
low pressure feeds fuel to the VST at about 68 PSI
medium pressure is the electric pump with a filter on it in the VST that feeds the high pressure pump at a CONSTANT 50 PSI.
high pressure is the belt driven pump that runs at about 625 PSI at ALL rpms.

Rod is that 68 psi or 6 to 8 psi

[rodbolt17]

6 to 8
68 would be an issue

[Sailmaster]

I was reading the fuel pressure from the schrader valve at top of VST? Tank

I had read that the test was 35 PSI minimum at this point or the Mechanical pumps need repair/ replace.

You are advising that this is the read point for the electric pump with filter inside the tank.

Therefore I need to service the filter in the tank

[rodbolt17]

either you have no fuel or limited fuel in the VST or the VST filter is clogged.
you should have 50 PSI anytime the pump is running.

unlike OX66 that does run about 35PSI and shifts the voltage to the pump at low RPM's this pump outputs a steady 50 PSI and runs at a single speed at all times.