If you must remove a power boat steering wheel, you may get lucky
after removing the center nut - but you probably won't.

Here's how you *should* proceed (rather than firing up the
Sawzall....)

First spray the shaft with releasing oil
Find a hub puller: that's a slotted bar with a central forcing bolt.
You have nothing on the wheel to secure the puller to, right?
NOW: drill two holes, and tap them for bolts to fix the hub
puller to. Tighten up: tap with a hammer, and bingo! off she
comes. Believe me that time investment pays off handsomely.

Brian W
with thanks to Edi in S.A.