Robin,
You're probably not going to like this answer. Considering that there is
no slop in your steering system, (check this at the dock) there is a natural
tendency for a mono hulled boat to wander back and forth. On a 23' Maxium
I've driven it goes through a slow 30 degree arc, about 15 degrees either
side of straight ahead. If I get it centered it will swing through this arc
back and forth. If the channel is wide enough I just let it alone, if the
channel is narrow I have to constantly counter steer. This I am told is the
result of the curved hull trying to compensate for the low pressure that
develops on one side and than the other. At plaining speed these forces are
absent because the boat is out of the water for most part. The pontoon boat
I used to drive didn't exhibit these tendencies due to the duel hulls that
were for the most part straight and parallel. All in life seems to be a
trade off. :-)
Paul

"Robin AndrePont" wrote in message
...
'93 Thompson 18' Mercuiser Alfa one, 4.3.

When in Forward gear (slow) the back end of the boat is going to the far
left and then to the far right, none stop. Yes, I have a Trim Tab!
I'm always fighting with the steering to keep this boat in a straight
line when going down a river or entering a spring when driving slow.
With full throttle it's fine, does not pull. I can Trim it up, or Trim
it down and you can look behind the boat and see all the zig zag bobbles
from the boat. You can actually see the water pushing from the Propeller
and see the water go from one side to the other; however, the outdrive
it not moving. Weird, huh? There's no slack in the steering. it's all
tight. The Power Steering pump is bad but I don't think that would give
me this problem.
Does anyone have any ideas???!!
Thank you
plz... no e-mail.