Really sounds like a bad fuel pump or clogged fuel lines. I am limited in my Outboard motor knowledge, but I have had fuel pumps die on me before.

Generally the symtpoms sounded the same.

Then again, since it won't crank, sounds electrical.

LOL, sorry I can't be more help.

How is the battery? The posts? Alternator? If the alternator or battery was going or had weak connections you may have to run at high rpms to keep enough power flowing to keep the motor running.