The standard propeller sold with small outboards has a pitch designed to help inflatables and other small dinghies get up on to a planing position and therefore go quite fast. With sailing boats like ours, we rarely plane and only when sailing in high winds and surfing down the front of a large wave. Never with the outboard, unless you have one of those newfangled sailing speedboats like the Coast 250.
Like David, I bought a high thrust/Saildrive/Sailmate propeller for my 6HP Mariner and kept the old standard propeller as an emergency spare. It’s impressive how the new propeller pushes my boat through the water on low revs, saving fuel and keeping the decibels down. Pushed harder, it can easily cope with a strong wind on the nose and fast currents. Provided always, as Matthew points out, that your carburettor hasn’t been gummed up with supermarket petrol, which contains ethanol. The remedy for that is to only use Aspen fuel - three times the price but free of ethanol. It has a very long shelf life which is useful if, like me, you don’t use your engine that much.
