A sail boat is a sailboat!

The reading can be either the on'yomi or kun'yomi, and you know both.

Between the two, the on'yomi はんせん is the standard reading. As is often the case with on'yomi compounds, it has a more technical feel, so it is commonly used in formal references to sailing ships either in technical books or fiction.

The kun'yomi ほぶね, on the other hand, has a softer, more traditionally Japanese tone, like how people in the past might have referred to it in everyday life. You'll often see it in older songs or literature, but it can also appear in modern works to convey a nostalgic vibe.