Boat speed under sail, what should I expect?

[phanakapan]

36foot 11 ton unladen steel Liveaboard overloaded cruiser. On recent long trip passage planned on 100nm per 24 hours. Just looked at my plotter out of curiosity and saw the stats- yup, over 30000nm we averaged 4.3knts. But look at the max speed- 17.9knots!!!! I do seem to recall surfing then falling off an enormous huge wave a couple of times- immensely loud noise of the prop thudding and whirring...

 

[Bobc]

On a transatlantic, we were averaging 150nm/day (so about 6.5kts) in a Bav49. Managed 200nm one day, which I thought was pretty good.