Why is the boat stuck, and how can I unstick it

If you really need to climb the hill (and can't go through or around it) then the ways to get a train to maintain speed as much as possible up-hill are:

• Make the train weight less (with less carriages, usually).

• More horsepower. Fit a stronger engine, or consider using multiple engines per train.

• Make the incline shallower. Since all inclines are the same angle of slope, you can only do this by "spreading out" the hill. Ideally the train should only have one upwards hill section under it's length.
  Here's an example of what I mean that I just threw together, notice how the train is 5 squares long and the hills are 4-squares separated:
  

All these assume you have realistic train acceleration enabled (and you really should - the original acceleration model is really slow on all hills, where realistic attempts to simulate momentum).

Also, if you want to tweak things a little bit in to your favour, you can change the calculated steepness of slopes if need be.

The station has to accept goods:

To do that it has to have enough commercial town buildings within its catchment area (it doesn't matter that the whole town has enough, the individual buildings must be near the station!) to generate a full demand of goods.

This Small Office Building, for example, only provides one eighth of a goods need.

While this Highrise Commercial building provides one half (four eighths).

There has to be enough buildings of this nature within a station's catchment area for the total goods demand to be at least one whole.

These buildings appear much more frequently in larger towns and cities, and tend to be clustered near the centre of the town - and again, your station must have them within it's catchment area for this to work.