They're actually great engines, simpler and easier to maintain and repair than a diesel.
Diesel power has a shed load of advantages for sailboat propulsion
, but if we're talking about bay and coastal sailing on a smaller boat used for mostly short sails
for the fun of sailing where you can almost always choose not to do a long motor
, then the advantages are somewhat academic.
No one mentioned the other huge advantage of petrol power -- dramatically fewer fuel problems, no diesel bug, etc. This is a really big advantage especially for a boat where the engine
is not used much except to get on and off the dock
Yet another advantage - no one wants them, so boats with A4's will be cheap