Alan. Yes, the ECM would make some compensation for a lack of load, mostly injecting timing and ignition timing, but it doesn't directly control the fuel pump. From Chapter 18 of the Helm Shop Manual...
"The nucleus of the system is the ECM. The ECM receives the operating condition of the engine and other types of information from various sensors and switches, processes the information and outputs signals for optimum control of the multi-point sequential fuel injection system and direct ignition system.
The ECM also supports the system self-diagnosis function and the alert warning system.
The PGM-FI system provides the following controls.
Basic controls -
Controls the fuel injection system, ignition system and idle air control (IAC) valve according to the basic programs set for startup and operation.
Correction controls to cope with changes in operating condition, the PGM-FI applies correction controls to the basic controls for the fuel injection system, ignition system and IAC valve on the basis of the various types of operational information.
Device controls the VTEC system, variable intake system, fuel line cut solenoid valve, high pressure fuel pump, etc. Fail-safe controls When a sensor or IAC valve fails, the PGM-FI uses preset values to allow the engine to operate without any problem.
Alert/warning controls
Activates the engine oil pressure, overheat, alternator, water level sensor full alarms, and also controls the overrev limiter.
Self-diagnosis function Stores a sensor or IAC valve fault in terms of a diagnostic trouble code (DTC). When the service check connector is short-circuited by the SCS short connector, the malfunction indicator lamp (MIL) is made to flash the number of times associated with the DTC."
Okay. I called and had a buddy go by the house and take the prop off and put it in a tub. He said he was able to hit 6k in gear without any hiccups or hesitation. What does that tell me it is or is not? Does this mean the ecm/ecu is good? Maybe a pinhole in a new hose? Would a little bitty teany tiny pinhole really make that much of a difference????
I want to remind everyone, I am NOT a marine mechanic, but just an owner of a 2007 BF 225 that tries to do all of my own maintenance and repair. So, what I write on this thread is based on my personal experiences, from reading a lot of the Helm Shop Manual, and from being an active member of this forum since 2008.
Question one - did your buddy run the engine on an axillary tank or the main tank?
Given that your buddy got 6000 rpm running in a barrel without a prop, I would say that there is a 95% probability your ECM is good.. It also pretty well eliminates a fuel blockage or air being sucked into the fuel line - but it does not entirely eliminate that.
The main difference between running the engine under load and no load is that the ECM will change the injection timing and the firing timing. Also, because of the vacuum difference between load and no load, the fuel pressure regulator will return more fuel to the VST under no load.
Next question, I know you changed out a lot of the fuel system parts, but did you change the fuel pressure regulator? Whether you did or not, go back to that and thoroughly check the vacuum line to it and make sure there are no kinks or obstructions to the fuel line that goes back to the VST. That is, there is one fuel line going into the regulator and two lines coming out. One goes to the fuel rail(s) and the other is a return line to the VST. If the vacuum is screwed up under load, too much fuel may be returned to the VST and not enough sent to the fuel rails.
As several have recommended, I strongly suggest that you check the fuel pressure. At idle (600 rpm +/-) with vacuum line to the fuel pressure regulator removed and clamped shut, you should read between 41 and 48 PSI. Speaking of fuel rails, you said that you replaced them. Did you also replace the fuel screen on the starboard rail?
If your post was a new one, the first thing I would have recommended is to check the prop. You said that you did that. Given the size and weight of your boat, your prop should be a 14.5" diameter X 15" pitch, or something very close to that. What precisely is it?
Finally, I don't know what throttle control system you have at the helm, but I would go back through that with a vengeance. Get your buddy back and have one hold the throttle lever at the engine while the other operate the throttle at the helm to make sure it is not slipping when held under pressure.
Beyond that, with current information, my brain is out of ideas.
