Might want to consider a sail cat and simply pull the mast
(or keep and have a really great antenna
plus backup propulsion). This will give you a lot more options as the sail market is much larger and far more of the sail models are outfitted for long distance cruising.
For long distance, you are going to be limited to displacement
speeds anyway, so a pair of 20-50hp engines you get in a sail cat are just fine. It's certainly possible to add additional tankage to boost the range.
Our little 34' cat with an outboard
has a range of around 360miles and if I was willing to slow down to 4-5kts, I could probably boost that to 500 or so without increased tankage. I'm sure a 40' diesel
ran at economical speeds could easily be set up to give you 1000mile range or more if you add an extra tank or two.
Keep in mind if you are looking at 900miles to the galapogos, you probably want something more like 1500 mile range in case you run into issues like strong head
winds or adverse currents. You don't want to plan on coasting in on fumes.