H-A
You might like to contact John Crighton in NZ and have a look at the Bermudan flea boat that a few Kiwis are building as a 20-footer for their events.
It is pretty fast, large-ish and DEFINITELY a displacement design. On race results (elapsed time / distance) they were doing about 9 knots with stock as a rock Silver Centurys on the back and two ADULTS aboard and gear to a minimum of 150kg.
Although, to be honest, your skiff was not 'planing', ergo it must have been in 'displacement' mode (or at least, semi-displacement) so I dunno what they were complaining about!
The boat Raoul lent me for the Waikato with one of Ross's motors on it (plus cav plate) was doing 12km/h (6 knots) and there is no way that boat was planing, so it would have come close to breaking the harbour 'speed limit' too.
If they want a 'race', or at least, a 'competitive event' and boat speed can't be the only deciding factor, then they need to come up with a different formula.
Like 4WD triallers do in some events, where you have to build a bridge over a gully and drive a vehicle over it; or remove a wheel, strip it to bare rim, re-assemble and drive on to finish.
Or the boating equivalent, if you see what I mean. Maybe remove motor from boat while afloat and change a prop, or a plug, or something.
Just ideas....suggestions.....
Or maybe just boycott their silly event altogether???
