need help intermittent spark on 2005 Sea Doo sportster 4 tec

[Scubadave16]

The boat ran great when put away for the winter. seemed to run OK in driveway although at idle and only for a few seconds. Ran OK on the run down the channel to the lake, but as soon as I hit the throttle I lost power and got backfire in the engine. it ran quite rough. occasionally it would seem to run normal and smooth for a few seconds, then back to rough. at idle it was rough and when i hit the throttle there was a rather consistent backfire in the exhaust i guess. Maybe?? i could smell fuel in the exhaust, but not really sure. so i pulled each spark plug boot and number 2 (the middle one) had no effect on the idle whereas the other two made it much worse. the boot seemed OK, but I didn't have any tools to pull the plug.

anyway before i start ordering parts I wonder how to approach this. I would think to first change the plugs since 95% sure it is a spark problem. but would a bad plug "get better" for a few seconds and then get bad again? i sort of assumed they were an all or nothing deal. I read on some semi related posts about trimming the plug boot and such. others talk about replacing the coil. I don't really see a coil per se. perhaps it is buried somewhere? if the coil, wouldnt all the plugs be affected? or is there one for each plug?

just wondering if perhaps some other odd problem is going on and if there is some different place i should be looking.

 

[ski-d00]

That's exactly how the plugs fail in 4tecs where they surge back to life for a few seconds. Don't overthink it and change your plugs.

 

[mkov608]

Do you have any diagnostic trouble codes stored in memory?

 

[Butchyb]

My 2005 GTX was doing the same thing when I bought it used-- Pulled No. 1 cylinder boot and that had no effect on rough idle, whereas removing No. 2 or 3 made things much worse. I was advised to replace the questionable boot ($120) and that was the answer. I understand the boot itself is a coil, and they go bad.