1997 200HP Mariner EFI loss of power on acceleration

[Sunny Jim]

Picked up a 1997 Mariner 200HP EFI motor recently. Reinstalled the oil injection system, which had been removed by the former owner. After putting it into the water I found that the motor would not accelerate beyond 2000 RPM. I checked everything. New switch boxes, had injectors tested and cleaned. All new fuel lines, rebuilt low pressure fuel pump, checked electric fuel pump. Replaced stator and trigger. Flywheel is OK. Checked Voltage regulators. Checked fuel. No matter what I did, nothing changed. Has anybody experienced a failure of the injector drivers or the electric fuel pump drivers in their ECU? It's been sitting at the mechanics shop for almost a month now, and they have yet to find anything wrong after I spent countless hours going over the whole engine myself. They tell me that the computer says the ECU is working OK. I wonder.

[EuropeanAM]

It will help you to receive faster, and more accurate responses if you will post your questions in the appropriate forum:

Mercury - 2.0/ 2.4/ 2.5 Liter High Performance
For discussions related to 2.0/ 2.4/ 2.5L motors (Carb, EFI, Optimax or Racing).

Is the throttle actually advancing to the wot POSITION?

It is possible to install the arm on the oil pump with it 180-degrees off, which will limit throttle travel.

[Sunny Jim]

A solution for this problem may have finally been found! I'll find out next week when the motor is back together, I'll let you know.

[Sunny Jim]

A solution for this problem may have finally been found! I'll find out next week when the motor is back together, I'll let you know.

OK. Here's the solution. After looking at everything electrical, the problem was finally located in the fuel pressure regulator on the VST canister. Seems that there is a very small filtering screen inside the pressure regulator and that had some crud obstructing the fuel flow to the injectors. Everything runs OK now that the screen was cleaned out!

[EuropeanAM]