Does anyone know why the game stutters so much? It runs at 60fps, but when moving quickly and especially when jumping the game skips frames like mad. Was it always like this and I just didn't notice as a kid? Is it a problem with DOSBox? My computer is more than powerful enough to run this smoothly..

This is just a repackaging of the base game with no improvements, yes it had stutter, it had plenty of limitations, it was a poorman's PC platformer.

Also make sure you have not accidentally enabled "slowmotion mode" from the escape menu

No, it was not. You needed a Pentium back in the days to play this real good but it was known for its fluid gameplay and I experienced it as such.

https://www.youtube.com/watch?v=HVfj2-4Vmek

It's the same with the GOG release btw. Tested it yesterday and it's running smooth as butter. No frame skipping or anything like that. I could upload a video as well (the ones above was not taken from the GOG release) if wanted (in the hope the capturing would not destroy the fluidness). I guess the problem is DOSbox config which might work different on each PC so it might be tweaked so that it will work on some PCs. You could try to contact support and see if they have some suggestions. Normally I also use Daun just to prevent screen tearing and such but I was surprised how good this worked (at least on my PC) even with the GOG included version. Still worth a try of course if problems such as posted by the Op do arise.

I think that vsync feature into Daum version it doesn'work... (this with Heretic1)

I'm experiencing this too. GOG's DOSBox games usually work well for me, but this one has many problems. Besides the frame-skipping during gameplay, on mine there is also a momentary freeze right when the intro starts, another on the level loading screen - as the view zooms towards the planet there's about a second's pause or more. Finally, right when the level starts there is a one, maybe two second pause.

Another problem: Setting 'output' to anything besides the default, 'overlay', causes the sound and animation to stutter beyond belief; I mean unplayable. Seems like 5fps or something. Opengl kind of works, but only when run as an administrator, and even then, there is very bad screen tearing.

I've tried excluding the game from virus scanners, running it in a clean boot environment, various compatibility settings, and within the config: changing the cycles, cpu, memsize. Nothing is working so far.

p.s. can't run the exe from within the directory: "This app can't run on your PC" (Windows 8.1). I have to use the Desktop and Start shortcuts, which is fine, but I'd like to be able to rule everything out.

Sorry for the double-post.
I tried that SVN build. Thankyou. It seems to improve things performance-wise. Thing is, in fullscreen the game is only taking up a tiny portion of my screen and I don't have a clue which, out of the 995 million options in the config, to change in order to correct this.

*Edit* Fixed. I'm dumb. I'd forgotten to delete the old GOG Dos config file.

*Edit: The Sequel*
Well, turned out most of the screen was cut off with this SVN thing. I then messed about with the DOSBox settings and somehow corrected that. After playing for a while I can safely say that SVN Daum fixed the long pauses at the start of levels and such. However, the brief frame-skipping during gameplay is still present, at least for me. Afterwards, I somehow messed-up the screen again, cutting half the image off. I can't fathom what's causing it.

I use Dosbox ECE SVN

http://blog.yesterplay80.net/dosbox-ece-en/

Currently, DOSBox ECE differs from normal DOSBox in these features:

Emulation of a 3Dfx Vooodoo card through OpenGL (No external Glide wrapper needed!)
4x, 5x and 6x scaling in windowed mode is possible
Pixel-perfect output mode for undistorted scaling of the picture
Improved emulation of OPL3 (a FM sound synthesis chip from Yamaha)
Improved sound of PC speaker emulation
Emulation of the Roland MT-32 midi synthesizer
Integration of Fluidsynth (a software MIDI synthesizer with Soundfont support)
Support for up to 10 joystick axis and 2 D-pads (full use of two 360 compatible controllers)

Yeah confirming this version works really well - backup the DOSBOX folder, then copy the contents out of this zip into a new DOSBOX folder in the same location. The shortcut will still work for you.

I wonder what's wrong with the original config/DOSBOX though as I'm sure I've run the CD version just fine in the past.

I also had stuttering / frame drops a lot with this. I did some testing and the following worked out pretty nice with my Nvidia card:

1. Switched to DosBox CEC build
2. DOSBox settings:

[sdl]
fullresolution=original
windowresolution=original
output=openglnb

3. Nvidia Control Panel (settings for dosbox.exe):

Vertical Sync: On (smooth)
Triple Buffering: On

For some reason this increases the stuttering and slowdown in menus and the transitions, but also makes the gameplay itself buttery smooth for me.

You also get the performance boost without Vsync enabled, but then you just have to live with some tearing.

It doesn't work properly with my display... there are vertical black borders...

I want to emulate scanline but it doesn't work properly too... (and this also with original 0.74 version)

and for now MT-32 and Fluidsynth features it doesn't work...)

Sounds like you're all having more luck than me. I'm still trying to mount it.
Is there any way to get this thing to work without mounting? I'm pointing it to C:\GOG Games\ and it's telling me it doesn't exist.

Like this: "mount c C:\GOG Games\"

or "mount c C\GOG Games\JazzJackrabbit" (where I put DOSBox ECE SVN)

*Edit* Got it working. Thanks voltage. At first I tried popping it in the game folder, but I'd just chucked the whole ECE SVN folder in instead of creating a new one called "DOSBox" like you'd said. Thanks petran79 for suggesting the ECN as well. Now to try some settings to reduce the stutter ...

Because people experienced problems with Epic Pinball I've made a .conf for Jazz Jackrabbit as well.
I don't have this game on gog but tested it on my cdrom version and it works well.

Try it at your own risk and make backups!
At the moment I don't know the correct filename of the .conf but made a best guess, correct it if necessary.

https://drive.google.com/file/d/1G7hEgo9-MoBysbqNqfJXYfAGpLeG8LLW/view?usp=sharing

Also don't use opengl or openglnb as it will cause the sound to stutter, just use ddraw or overlay.
As for the screentearing, I can live with it but this is a shortcoming of Dosbox at the moment and can't be easily solved to my knowledge.
My config of the game, Soundblaster 16 and Pentium systemspeed.

Tried it. Excellent! Yours is the most successful so far. Aside from a slight pause at the start of the level and the aforementioned screen tearing it works great! There was no choppiness whatsoever during the actual gameplay.

My previous best was to have no screen-tearing or choppiness during the level, but .... horrendous, massively increased lag and sound-stutter during menus as well as a longer pause right before the level.

I think I used DDraw *or maybe overlay - I forget* (no other real tweaks) and forced Vsync on (Graphics card side); this eliminated the tearing, but increased the stuttering in the menus. I can recreate this effect using your config, Strijkbout. However, with the way I had it set up, disabling Vsync meant the return of the slight stutter during gameplay.

So yours is definitely the best all-rounder in my opinion. Thanks again!