Hi everyone! new to the site..need advise on the very common ss xi bogging issues.. here's a bit of info:

I have 2 93' ss xi 750 dual carb jet skiis, which have ran great for many years. One of them has been acting up frequently the past couple years which has vortec carbs and req's high octane fuel.
Last weekend I took it out and it ran good for about a half tank, it randomly stalled on me twice within 30 mins., then started bogging down and dying shortly after if i gave it more than 1/4 throttle. it would start and idle fine, but 1/4 throttle or more and it would fall on it's face..so i putted back to shore and then wouldn't start at all. i let it sit for a few mins., it would run and idle fine then bog and die with throttle.
So i loaded it back up and we just ran our boat the rest of the day...

When I got it home..i checked everything out:
-pulled the filters...throttle plates and barrels are super clean
-choke and throttle cables and levers operate fine
-plenty of oil and fuel (fuel mixed with octane boost-108 oct)
-pulled plugs..fouled and oil soaked(drops of oil), gap perfect
-peeked into cylinders..rear cylinder very wet with oil/fuel

I replaced the plugs, hooked up the hose and ran it...it revs up just fine on the trailor with new plugs (no load/out of water/cold)
Water spits out the side vent and everything

Worried to take it out again and get stranded!
Note: Carbs just rebuilt by Kawasaki last summer, and we usually have to swap plugs on the problem child each trip..

I guess I'm really looking for someone with the same experiences to point me in the right direction, just wanting to see if i can nail it on the head before having the dealer fix it. I've read a lot of older posts with same issues but nobody ever responded...hopefully someone out there can help me out

(Hoping that it was just fouled plugs, but just worried because a lot of other people have experienced this and replaced just about everything with no results...have had no warning lights or overheating...it smokes pretty good, but i just assume rich mixture and normal oil smokage-new to jet skiis and 2 strokes)