18 GTX 300 Runs Rough wont exceed 40mph for 10 minutes

[18GTX300]

This entire season for the first 10 minutes the jet ski runs horrible. It wont go over 40mph and feels like learner key/touring mode is on, even in Sport.

Once the engine is warmed up its good for the day. (Hits 71, drops down to the governed 69) If I ride the next day it's also fine from the start.

If I dont ride for a week, when I take it out, it runs horrible for the first 10 minutes again.

The longer it sits. The more noticeable the issue is.

52 hours. Changing plugs now.

Any ideas? Sti under extended warranty, but that's always a pain.

 

[18GTX300]

Front cylinder spark plug was really wet and not a the same coloring as mid and rear.

Could this be a coil issue?

 

[Mister Magoo]

If the ski is under warranty this would be a good time to take it as you could have a more serious problem than just a spark issue. Sucks though going to the dealership during the season. The coil packs are interchangeable, move the front coil pack to the rear cylinder and see if the problem follows the coil pack. Would not hurt to do a compression test.

 

[18GTX300]

It was definitely the plugs. Running great over multiple outings. Case closed.