I have twin Yamaha 150s 1999 OX66s and have not had any fuel related problems. Just make sure you have a good fuel/water separator in your system and drain it regularly ,Yamaha recommends a 10 micron filter. I also use stabil marine fuel treatment [the blue stuff] . If you replace your low pressure fuel pumps I would recommend you get them from Yamaha as I believe it is one of the up dates for these motors, was told that the after market ones don't hold up as well to ethanol. I just reread your post and see you just bought it. Its recommended that you replace or rebuild the low pressure fuel pumps every 4 years. If you get a hole in the pump diaphragm, fuel will enter the crank case and detonate [not a good thing] other than that these motors have a reputation as one of Yamaha's most bullet proof motors
congratulations on your new boat

Don M