You can use either a siphon or electric gas pump, if electric make sure it's for pumping gas, go to local auto barn and get something 12V and cheap.
The siphon will work fine since the boat tank is up so high, well over a portable tank placed on the ground.
Jack up bow as high as possible, that's the ticket. First pump until dry w/o jacking bow, then jack to see if more comes out. Keep jacking as more comes out
Some gas will remain in tank, I'd say about a quart or so.
If you want the quart, will have to pull the sender and rod it out.
Use gas in lawn mover, especially last few gallons of it. It may come out darker in color.