Into the wind I’m sure a 4hp engine will, on average, outperform a 2.5hp (for example). It’s easy for a motor to get a Wayfarer moving through the water at or near to hull speed in light or no wind, but full power and the full concentration on the helm are required into a F5 or F6 breeze. These are the conditions in which the extra power starts to count. However, few of us are able to choose our outboard to suit the conditions on any given day, but must find something acceptable over a range of conditions. It’s a compromise between power, weight, convenience, fuel economy, reliability, acoustics, capital outlay etc. Most keen cruisers seem to use outboards around 2.2 to 2.5 hp.