Typically, most longboats had around 30–40 men — assuming you're talking about longboats made for raiding. Norse ships were made for many different tasks: there were warships, cargo ships, fishing boats, and of course, raiding ships. read more
You'll have to define which kind of longship. There were several, including the drakkar and knarr. A longboat would have been a faering, with an average crew of maybe four or five. read more
The average speed of Viking ships varied from ship to ship, but lay in the range of 5–10 knots (9.3–18.5 km/h) and the maximum speed of a longship under favourable conditions was around 15 knots (28 km/h). History. The Viking longships were the epitome of naval power in their time and were highly valued possessions. read more
If you check the Icelandic sagas, you will see many instances of people going a-viking with one or two ships; but it is not clear whether this is typical of continental Scandinavia, which was much wealthier and also more centralised. read more