Dave --
If this is what you are reffering to --
http://www.westmarine.com/webapp/wcs...&classNum=null
We have had experiance with them -- They are quite good and are very easy to put up & take down. Storage may be an issue as they are as large as a collapsed table umbrella. This could be a consideration if you have a smaller boat.
The only negative that we found is that they do not handle WIND very well. I'm not talking about a soft breeze - but if the wind kicks up they begin to be a challenge. We've had one actually invert (much like a rain umbrella) and bent permantly one of the supports. For 60-70% of your needs it's a GOOD DEAL !!