Vst or not ? Yamaha 250 hp 1997 ox66 salt water series

[wellcraftv20step]

I ve been out a couple days this week fluke fishing I noticed that at the end of each drift when the engine is still warm I'm having trouble starting it again, I've actually had to advance the throttle/shifter to get her started then quickly put her in gear and goose it till I get moving. It starts and runs perfectly when cold, it runs perfectly when under way and at WOT it's just on warm starts.. I cleaned the o2 sencor at the beginning of this season and found it to be spotless, yesterday I pulled the water separator and emptied the contents into a glass to find no water or debris but still changed it anyway , I changed out the gas filter but it also seemed pretty clean. Still the same problem .I guess my next step is going to be the vst filter or should I be looking elsewhere ?