F25 LWC stalls going into neutral

[FLBADAXE]

I have a 2017 F25 WLC with close to 500 hours that is running at about 3200 rpm at WOT and stalls when I back down the throttle into neutral. I do standard service religiously and it has brand new fuel filter, spark plugs, etc. It appears the fuel pump is working properly as the bulb is always full and has a reasonable about of pressure when running. I gave it an extra squeeze while backing down to see if that would prevent a stall but no joy. Before I go diving into the injector pump, is there a more simple cause I could be missing? The motor is mounted to my home built floating tiki bar (not a trailerable model) so I would have to remove it to take it to a dealer.

Thanks!

[99yam40]

I would check the IAC valve.
Idle air control valve

running at only 3200 at WOT means it is overloaded or something is wrong with the motor.
should prop to meet WOT spec for the motor
but that is not a boat it is a barge
probably needs a high torque T25, different gears and prop

[FLBADAXE]

Thanks for the response! An IAC would certainly make sense but I can't seem to find that part anywhere on the diagram. Is it possible it's built in to the throttle body?
Good call on the propeller, I rarely take it above 2000 rpm as it's purpose is more leisurely cruising but I did note that it used to be able to hit 4500 or so in the current configuration. Something has definitely changed.

[99yam40]

I have no idea where it is or if it has one, I just thought the bigger 4 strokes have one so the little ones would also.
maybe it just uses a dash pot to slow down the throttle closing off

[FLBADAXE]

So I replaced the prop with a lower pitch to get a better RPM range. I noticed that after a start and short idle, If I do a WOT, it goes right up to 5000+ RPM for 5 to 10 seconds and then slowly loses power down to around 4000 rpm where it will hold. It is still stalling when I pull off throttle. I tested a new tank with a new short fuel line and bulb: same issue. So strange. Could it be restricted air flow?

[FLBADAXE]

Ok, I dove in and 99yam40 was right. there is an IAC motor on the throttle body but I cant find a replacement part. The only marking on it is J6927B and no amount of internet searching came up with a hit. Do I have to replace the entire throttle body?

[FLBADAXE]

Incase anyone else has this problem, I removed the IAC unit to examine it and replaced it and the problem went away. Not exactly sure what i did to fix it but i may have inadvertently changed the position. Not sure about this motor but in some automotive applications, the ECU will notice that is not the last position commanded and forces a calibration. Can't say for sure that is what fixed it but definitely related to IAC.

[99yam40]

well good for you, glad you got it fixed.
thanks for coming back in to update what fixed it