06 250xs Surging Mid-Range

[Errolml]

Serial Number is 1E000918

My 06 250xs with 280hrs is surging from time to time. First off I recently swapped from a 02 promax 225x to this 250xs. The motor from what I was told sat up in a warehouse for 10 years. The guy I purchased it from changed VST and plugs (gapped at .032), the exhaust tube was also cut and mid section changed from 25" to 20".
The first time I took the motor out it surged at 5100-5200 rpms, the only way to get it to stop is to back down on the rpms and slowly get back in it. It doesn't happen often but at least 2 times in a 2 hour day of run time. However just recently it did it to me after about 5 min into the initial run of the day, but this time it did it at 4100 rpms and was much more aggressive than the previous times. After the problem occurs my holeshot goes down the drain for the remainder of the day. I am kind of thinking it may be a coil going out because of the inconsistency of the issue. So far I pulled the filter on the VST to check for trash but it was clean, and I also drained both the low pressure and high pressure sides to look for H20 which was also good. I checked starboard side shrader valve for air. Let me also state that I don't have a separate fuel filter or water separator. Some insight would be nice on this issue, its driving me crazy.

Thanks in Advance,
Errol L.

[Rumshaker]

I have the same year motor and had a similar problem. I would definitely look at the issue of it being a bad coil.

Serial Number is 1E000918

My 06 250xs with 280hrs is surging from time to time. First off I recently swapped from a 02 promax 225x to this 250xs. The motor from what I was told sat up in a warehouse for 10 years. The guy I purchased it from changed VST and plugs (gapped at .032), the exhaust tube was also cut and mid section changed from 25" to 20".
The first time I took the motor out it surged at 5100-5200 rpms, the only way to get it to stop is to back down on the rpms and slowly get back in it. It doesn't happen often but at least 2 times in a 2 hour day of run time. However just recently it did it to me after about 5 min into the initial run of the day, but this time it did it at 4100 rpms and was much more aggressive than the previous times. After the problem occurs my holeshot goes down the drain for the remainder of the day. I am kind of thinking it may be a coil going out because of the inconsistency of the issue. So far I pulled the filter on the VST to check for trash but it was clean, and I also drained both the low pressure and high pressure sides to look for H20 which was also good. I checked starboard side shrader valve for air. Let me also state that I don't have a separate fuel filter or water separator. Some insight would be nice on this issue, its driving me crazy.

Thanks in Advance,
Errol L.

[EuropeanAM]

While I don't think the cut tuner is helping your cause at all, it would be wise to check for spark WHEN the problem is occurring.

Take a timing light out on the water- you can clip it to each plug wire, one at a time, while watching for a clean/bright flashing pattern.

[Errolml]

Thanks Don, I will certainly look into that. I have no doubt that the cut tuner has whacked my holeshot but Merc wants some change for another one!

[Savage]

Cut tuners have ruined a lot of performance for people......

[clay-wallace]

I doubt you have the same issue I had but Ill share it anyway. Recently my 2010 250 ProXs blew, and my local dealer put a new factory powerhead on it for me. It ran perfectly through break in, and for the first 2 or 3 hours thereafter. However at about the 7 hour mark it started acting similar to yours. I would be running about 4500-5000 rpms and all of a sudden it would just surge 3-400 rpms. No alarms or anything. Then shortly after it started having an occasional miss at similar rpms. Before the day was over it completely shutdown on me while running. I figured the head had taken a $h17 on me again, but I then realized that it had lost ALL power, wouldnt turn over, trim, nothing. I always keep a multimeter in the boat and after a little while of searching I found that there was a bad connection at the main power lug on the motor (the one where the starter, alternator fusable link, and relay power comes together). Cleaned all the wires up, replaced nut with a lock nut, and all was well again.