Merc 250 PRO XS RPM issue

[k2rider18]

Hello all,


My motor (250 Pro XS Model# 1251P73BD / SN 2B017333) is having an issue with getting above 2000 RPMs after the first run. Starts and idles fine but when you mash the throttle is just sort sounds like it’s bogging down. I took it to my local Merc Mechanic and here is what was performed:


Compression: 116-120 on all six cylinders 350hrs total hours with 50 on new rebuilt block.
Hooked up computer to the engine, check/test and errors. None noted.
Test all injectors, no issues.
No fuel in air rail.
Reeds looked intact.
Diaphragm looks good.
Test ran engine, fuel/air pressure were in specs.
Did find #2 spark plug wet fouled.
Replaced all spark plugs.


After picking up the boat, I went to the lake to run it and fish for a few hours. When it started up it coughed a little and sputtered, other than that it idled fine. Watched the thermostats open on the gauge and temps dropped as advertised. Idled our past the no wake and jumped up on plane and ran great. About an hour later I decided to pick up and move spots and went to mash the foot pedal, no joy. The RPMs would only get to 2000. I did meter my cranking battery x2 31G and it read 12.8 before putting it on the charger.


The mechanic said he will meet me at the dock on Thursday to run the boat with me. Prior to him showing up, is there anything I can check or visually inspect? Or really anything you guys would recommend looking at?


Thanks for y’all’s time,

[JOE54]

TPS sweep test after warmed up

[lpugh]

I have been seeing a few that the shift interrupt switch sticks in when warmed up causing this problem

[k2rider18]

Thanks guys, I'll keep this in my back pocket while lake testing the motor.

[JOE54]

I have been seeing few that the shift interrupt switch sticks in when warmed up causing this problem

and warning horn should activate if this happens indicating neutral overspeed

[EuropeanAM]

and warning horn should activate if this happens indicating neutral overspeed

Neutral Overspeed was removed in later calibrations.... so it may not necessarily log that on engines built after Jan. 2012.

[k2rider18]

So my wet fouled plug reappeared and was a coil going bad and failed at the ramp with the mechanic, swapped coils and the gripe followed. Tracker valve had a small tear in it as well that most likely manifested itself after running it, which was subsequently replaced. Leak down was performed on the fuel rails as well and yielded no issues. Motors is now firing on all six and no errors.

With 50hrs on the rebuild should I or is it recommended to get the injectors cleaned, flowed, and tested?

Thanks again for the help.

[EuropeanAM]

Were they done with the Rebuild?

[k2rider18]

Were they done with the Rebuild?

Yes everything was checked and flowed and clean

[EuropeanAM]

At 50 hrs, I would not expect you would need to do it again, then.

[k2rider18]

At 50 hrs, I would not expect you would need to do it again, then.

thank you Sir.