That's it. And definitely not a cruise - hard work. And back in the 80s, very cut off from home. Three weeks on average for a letter to go one way. 

Although 'on a route' was dependent on what our 2 or 3 person 'line up'  teams (who spent very little aboard as they were trained and often several months seeing government officials and planning with local churches) were able arrange. So a rough plan ahead for a year or more would be made. (we were usually in a port for 3 weeks or maybe a month) but it could change and sometimes entire countries would get dropped or heavily curtailed (like Indonesia where we were going to be for several months but it was revised to three ports in tree weeks or something. I'd have to dig out my schedule) 

It was a Christian mission ship so the idea was to take books in English and in local languages and sell them at local prices. About 30% of titles were Christian and the rest secular. We'd only go to a port if local churches invited us and in a port we'd also run conferences (for pastors or couples or kids or whatever), perhaps do tours of the ship which were popular, and visit churches. 

And yes I've considered designing a Traveller ship and adventure that would do similar - whether religious or for literacy (and medical would be an obvious one) - but I think it needs a more Dumarest type universe maybe than Third Imperium. 

 Or are their regions that might equate more to 'developing countries' where resources are hard to come by? 

tc