Thanks for all the constructive good advice.
"OHB- That worked just fine in the days before E10 gas and phase-separation issues. Not so much anymore where E10 gasohol is mandated, and in the case of separation, leaves TWO bad layers not safely fixed by pumping bottom layer and adding some new."
When this problem arose, I had over 50 gallons of fuel mostly new. When my mechanic first visited he advised that possibly all the fuel would need to be pumped out and disposed at a cost of over $500. As indicated by others, it is well known that if E 10 fuel goes bad it is not a simple pump out the bottom. I decided to try to burn off as much fuel as possible.
Since he rebuilt the Carburator, I have managed to burn off most of the fuel, although as I indicated before the engine would loose power in wake or rough water. I could not find K 100 but added another similar product and ran the boat with sharp turns to test. After several incidents of power loss, the engine ran well except the idle became very rough with some stalling.
I spoke with my mechanic this morning, and we have developed this plan.
1) He will provide a portable tank to hopefully allow getting to the hauling slip, may have to clean carb again to allow smooth idling. Check and change fuel filter.
2) The tank will be pumped out after the boat is on the hard- I think I found a means to legally dispose a nominal amount of old fuel. It will be left empty for the winter.
3) He will winterize the engine with a separate tank spiked with winter conditioner. He said he uses leaded fuel to winterize which is expensive to come by from a motorcycle shop. All gas stations sell only E10 in NJ.
4) I am suspicious about my fuel vent hose since it often fills up during refueling and prevents adding more fuel and may have contaminated the fuel. We are planning to replace that hose and inspect others. The vent hose has sometimes had fuel laying in it until I blow it out.
Again thanks all for the constructive comments. Hopefully this will not totally bust the boat budget, which a complete pump out would cause and leave an uncertainty about some hoses.