I am looking to install imco boxes on my boat(92 35 fountain) and have a few questions.
1. On the raised x dimension boxes do you have to move the whole motor up 3 inches or just angle the back up slightly?
2. On the standard x dimension boxes does it move your x dimension lower or make it the same as it started at?
3. Would it be better to just buy shorty drives or use the raised x dimension boxes?

Here's what I know. I just got done putting on Stellings boxes last season. Imco boxes will raise your props 3" and you will need to raise your engines the same 3" since Imco uses a straight shaft which is a longer version of the stock drive input shaft. I also believe that their shaft uses an XR joint so your gimble bearing might need to be changed as well. Your exhaust and rigging will need to be modified to work with the raise. Stellings boxes are what they call adjustable from a neutral position to 3"up. Neutral is actually aprox 3/4" up. Engine can remain in present location because they use a drive shaft system to connect to the drive. Down side to that is that it eliminates the rubber coupler, mating directly up to the flywheel via their so called drive saver which is just a metal disc designed to fail before the drive gears? Doesn't work but being careful on the shifts can avoid problems. I went a different route and retained the coupler, used drive line bell housings and transmission replacers with custom made drive shafts since we also moved the engines 2 ft forward. Not a cheap project but I wanted the rubber cushions using the couplers. If all you want is the higher props the shorty lowers are a cheap trial to see if you get the results your looking for. Easy sell if not. The Extension boxes are a major project, expensive and unless your doing over 100mph and need to get your props farther back into cleaner water, not really worth the effort. They look bad azz though. I hope I helped a little. Much smarter, more exp guy's will chime in and help, possibly add and or correct me too.

The Imco 3" raised boxes will require you to raise your motors front and rear 3" to accommodate for the raised box. The neutral box will require you to do nothing but realign your motor and if your lucky it'll raise your X like it did mine. It all depends on the degree of your transom they build in I believe 14 degrees into the box if your transom is less it'll raise it if it's more it'll drop it. It's a gamble.

Or you could go with the Stellings box which uses a shaft that you bolt right to the flywheel and you can move the box into 3 different positions. Neutral, -1, -2 this just requires you to unbolt the rear of the motor to change it and put it in the different holes.

Hope this helps.

My transom measures about 13 degrees as far as i can tell so maybe i will get some raise with the neutral boxes.I am skeptical whether they will help or not since my prop slip is at 12% already.i don't see it getting much better.But i have read that newer fountains have higher x dimensions so hopefully i am going in the right direction.I would also like to move the engines forward but hate to lose the room in front of them.

Before you do anything you should determine your current x dim or propshaft centerline.

Jeffswav makes a great point. To further that "research", go over to the Fountain forum and ask if 12" setback boxes are recommended on your year hull. Notched transom, ridepad etc. are designs features that you may have and not compatable with a box installation.

Im surprised you have that much slip with a stock 92 35. What props are on there now?