On Wednesday, March 18, 2015 at 6:00:15 PM UTC-7, Wayne. B wrote:
On Wed, 18 Mar 2015 16:14:51 -0700 (PDT), Tim
wrote:

Yes, at a very slow speed, the boat would back to the left only regardless of how you set the rudder, and that provided to be a royal pain in a few cases.

===

That issue is known as "prop walk" and it is most apparent at very
slow speed before the boat gains momentum. Prop walk is caused by the
propellor acting as a paddle wheel. Since the prop/paddle wheel
rotation is perpendicular to the center line, a side thrust is created
instead of forward motion. The direction of "walk" depends on the
direction of shaft rotation. Since your boat is walking to the left
we can assume the shaft is rotating counter clockwise in reverse (when
viewed from behind the boat). Remember to think of the prop as a
paddle wheel at low speed. There are other more complicated
explanations for why prop walk occurs but the paddle wheel analogy is
the most intuitive to understand and the easiest to apply to problem
solving.

As Richard pointed out, the rudder has very little effect in reverse
until the boat gains some speed and creates water flow past the
rudder. This is not a problem in forward because the prop creates
plenty of water flow even when the boat is standing still.

Backing up a single engine boat is an art form not a science. Every
boat is a little different but some basic priciples apply. The best
strategy I've found is to apply a quick burst of power in reverse and
then shift immediately into neutral. Once you are in neutral there is
no more prop walk, and if you have built a little speed, you can steer
with the rudder. Sometimes you have to do this more than once.

Another strategy is letting the prop walk work in your favor and just
let the stern "walk" in the direction it wants to go. This implies
some maneuvering room of course.

"Backing up a single engine boat is an art form not a science."

Yes, I found that out. and quickly. before pulling into a different landing than where my boat was slipped, I figured out in advance how to safely and effectually get out of there without harming other boats or whacking a chunk of dock.

Yes, a rudder boat is quite different than IO's.