Re: 1965 Johnson 33 super seahorse
Welcome to iboats! You'll find a lot of good advice and information here. I have a '67 33hp that I converted to a tiller steer and it's been a very reliable motor for me.
It doesn't hurt to do a carb rebuild, but the problem may simply be an adjustment of the low speed needle valve. As for the shifting issues, it's hard to say what it is by your description. It could be anything from an adjustment to the shift cable to the shift rod connection to a worn clutch dog. Considering the motor has been sitting for four years, it's best to have a complete "run through". Take a look at the "Top Secret File" that is a sticky topic on the Johnson/Evinrude forums. Also, invest into a manual. A factory manual is best, but at the very least get a seloc or clymer manual that covers a range of motors.
One other thing, you may want to post pics of any issues. As they say, pics say a thousand words.