[tsubaki]

Tapping on the steering arm bolt on location (whatever it is called that the motor arm attaches to) will deform the bolt hole, avoid that as much as possible.
First grab with a pair of Vise Grips, Channel Locks, or pipe wrench (taking care not to booger the shaft up too much) and twist and rotate the shaft (not at the steering arm connection end, it will turn freely).
The torch or a heat gun would be great if you were comfortable using it. I normally reserve that till last on stuff.
Trying everything from penetrating oil to mineral spirits to clean and lubricate the shaft and tube.
They seem to come free easier by applying pressure than whacking it with a hammer.
Finding a good way to push it out by prying with a 2x4 to a point and then incorporate a wood or metal dowel to assist going deeper into the tube would be one suggestion.
If you had the room (usually there's not) for a bottle jack, that would be great. Taking care of how much pressure you're putting on the fiberglass. If you had a (or knew someone) hydraulic ram set that would be a better setup.
Cleaning the tube needs to be aggressive, it has now swollen and needs honing, not just cleaning. I've tried brake honing tools, sand paper on drill bits, etc. One thing my father did on the last one was bought a masonry bit about whatever size the tube inside diameter is. While spraying with penetrating oil and jooging in and out with the drill was able to get it to the needed size.
And will somebody confirm or deny using ONLY marine waterproof grease in this (well all) location.