Need Help 250 Pro XS

[Bulletmafia21xd]

Motor runs fine at WOT but when running about 45-55 mph it's surging well not surging more like it's missing. Already had a new TPS sensor put on it thats what came up on the smartcraft.

[EuropeanAM]

Welcome to BBC!

Will be glad to attempt assisting with this.... if you could, please provide your Engine's Serial Number- and a more detailed description of the "studder, skip, surge or other complaint".

Does this occur at a specific RPM, specific throttle setting, etc....

Repeatable, or intermittent?

[hempbake1]

Also have this same issue. My miss seems to only be at wot. Very intermittent. Sometimes she runs like a scalded dog sometimes she misses. Tried new prop sat. wouldn't turn it 5700. stopped idled for a little bit then hit it again, bam bumping the rev limiter and had to back out of it. It misses like you shut the fuel off for a millisecond. It is at the dealer as we speak being checked out. This has been going on off and on since last fall. Talked to mechanic, fuel pressure is good, sparkplugs look like they're burning good, all coils have been replaced as per merc service bulletin, no codes, vst clean, no water in fuel, checking each injector right now. Don't have serial# as it is at dealer. It is a 2008 250 pro xs xl. any help appreciated.

[hempbake1]

Also i know that propping is critical, what am i looking for as far as RPMs in the correct prop? does running at 5750 or 5800 wot hurt, or do i need to be right at 5950-6000 wot with a light load? Rev limiter is 6300, so is it better to not load this motor too hard with too much pitch that keeps you at 5750-5800?

[EuropeanAM]

I recommend propping this engine at 5850-6000 RPM's, NORMALLY loaded.

Keep in mind- this RPM figure MUST come from a RELIABLE source: Either a Smartcraft Instrument OR an Inductive Pickup Tachometer.

Do NOT rely on an Analog Tachometer for this purpose- they are NOTORIOUSLY INACCURATE.

You may actually be hitting the limiter earlier than you think....

[hempbake1]

Have a smartcraft monitor. hopefully the tech will find out what is the missing issue. Don do you have any other ideas that might need to look at?

[EuropeanAM]

There are a lot of possibilities.... Computer Diagnostic would be the most helpful.

PRINTOUTS of the Run History, Freeze Frame (Fault) History and Fault Seconds Counters would be MOST useful (even if the tech "thinks" there's no faults).

Also, a DATA RECORDING taken with the CDS while the problem is occurring is an EXCELLENT diagnostic tool. This can be played back over and over, frame by frame, to watch for strange "blips" (such as BATTERY VOLTAGE and AVAILABLE POWER).