Sorry havnt posted here for a while - been trying to keep the Cornwall247 forum running - its hard work
Lightly loaded and one up in calm conditions the best ive had is 41.3 knots gps measured and cross tide. Thats with a Johnson 21" Stainless prop.
Normal use with a few passengers and a tank full of fuel would yeld 39 knots ish.
The boat is very light at 41 knots as trimmed right out to get that speed and in a heavy sea where the boat is jumping out of the water fairly regularly i like to trim in a little bit which shaves a knot or two of the top end.
hope that helps