vst issues again

Own a pair of 200 HPDI's (2004) (320 hrs). Over the last 3 seasons in Ct my engines VST's have chalked up on three separate occasions (within 50-70hrs of replacement). Each time I have had to replaced all filters at considerable expense; (Yamaha replaced a defective fuel pump on one engine). I have been using Startron with every fillup, along with the recommended dose of Ringfree. Symptoms have always been the same- when coming off a large wave, rpm cuts back +/- 500 revs. Looking for a solution.

[boats.net]

If you have a aluminum gas tank it may be an ethanol related problem, ethanol will clean inside of tank, removing oxidation.

Aware of that one. I do have aluminum tanks. We've been on ethanol since Ct switched from MTBE about three years ago. Thought that the "cleaning" would be over by now (a few thousand of gallons of fuel later). Looking for suggestions.

[Dennisg]

at the risk of sounding like a dummy, What is a vst ?
Dennis

[gecsr1]

vapor Seperator Tank