Just wanted to share my experience with the shift linkage problem. From what I've researched this is a widespread problem, the linkage rusts out and either twists or breaks making the boat not shift or stuck in any of one gear. If you run into this and research it like I did there is the dreaded task of removing the powerhead and replacing the shaft. While  my girlfrend was researching this she  found a new product called the "Shift Shaft". It saves the trouble of removing the powerhead since it is a 2 piece design. It cost abt. 80 bucks more than the Yamaha piece but the labor is abt. an hour if your familiar with pulling the lower unit as opposed to an all day job. Just thought I'd share as many V20's have Yammies and this problem will crop up and I here the old way is a hell of a job, with busted bolts, rusty bolts, torching....... you get the idea. Here's the link  
http://www.shiftshaft.com/  hope this helps someone like it did me.