Yes, with no problems at all.
No, Yamaha's TTR lineup is all 4 stroke motorcycles.
50:1
The dry weight of a 50 hp Yamaha outboard of the 2 stroke variety is 158 - 187 lbs, depending on the particular model.
The mixture ratio for Yamaha outboards is 50:1 gas/two stroke oil. That is approximately one pint of gasoline to a plastic coke bottle cap full of two stroke oil.
The correct ratio for 1991 85hp Yamaha is 1:50. 1 liter of oil for 50 liters of fuel.
50:1
Torque for 50 hp fore stroke casing bolts
Assume you are talking about a boat and a water skier. Yes it will work. I have been towed by a 35 HP outboard. It depends on the skill of the skier to be able to get up quickly. It also depends on the skis and the drag they cause while being pulled from the water.
A non oil injected, 1990 model, 2 stroke Yamaha outboard requires a 50:1 ratio, one pint of 2 cycle oil, to six gallons of fuel.
The fuel mixture for a Yamaha 40 hp 2 stroke outboard engine is 50:1, gas, oil mixture. You should use new gas when you get the engine ready for the season.
4 stroke oil 20W 50 or 10W 40 doesn't really matter
You really can't, the model hadn't changed much in those years. Just a 50cc four-stroke Yamaha dirt-bike.