pro xs got a miss at high speed

[cleo jennings]

I’ve got a 2008 Mercury pro 250 pro XX that at take off has a sluggest start and then at high speed on plane it has a miss?

[Jtreed99]

In the words of the wise and experienced board member Savage “perform a spark test as the problem is occurring.” If it’s a quick miss it may not be fuel delivery issue but your motor is of the age that it may be time for fuel lines and pulse pump per the sticky in the FAQs. Also make sure maintenance is up to date especially on plugs. Visibly inspect coils for any cracks in the potting, especially with white foam oozing out. Beyond that I had a similar issue once caused by water intrusion into the cowl, common sources for this are water pressure line leaks or missing rubber plug in lower cowl so check for any water spotting on or near the electrical plate at the rear of the engine.

[EuropeanAM]

If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

Cleo- what boat is this engine mounted on (also)? Prop/Setup info?

[Kb444fishing]

Seems a lot of us have similar problems. You will find many things can cause it. That's why they say start at the beginning . On mine I started was it ignition related or fuel. Started the ignition way and after a year of chasing it fixed with fuel rail injector etc cleaning. Mine had 600 hr Don says 400 it should be addressed. Not saying this is yours just saying it could be. Mine was an 08 also.