Hey first time poster here, absolutely love the site!
I remember playing this game as a kid and I have been wanting to check it out.
I got all my controls mapped out and as I was playing I noticed that when I press and hold 
the jump key Jim just barely moves off the ground and just keeps jumping barely if I hold the button.
I have tried all sorts of button combos and cannot get it to work...Am I just totally missing something or
has anyone else had the same problem?

Thanks!

That's strange, maybe the button settings on the emulator are set to turbo, I don't know, it never happened to me. If you want to set up the controls you do the following if you are using the SNES you do the following.

1. Push the escape button and you will see a bar on the top of the screen.
2. You will see several options on the top of the screen, click config and you will see several more options then you click input.
3. You will see all the buttons you have to use to play the game, there is a little area with the turbo buttons. It would usually be blank, but if it has buttons on the key board on it then your pushing a turbo button. 
4. To switch buttons you simply click on the space next to the letters which were the buttons used on the Super Nintendo controller and then you push whatever button on the keyboard you want to use for the game, it's like configuring your own controls to get rid of the turbo buttons you do what I mentioned and click escape to get rid of it.

If you are using it on a Sega Genesis emulator then I don't know what to do, that's something you should ask in the retro game room help form. Then someone who knows more about the website the I do will answer your question

Metalhed2434 : Sounds like you have one of the keys set to turbo. I suggest re-mapping the controls.