It is difficult to make absolute statements about engine variables... But, increasing the pitch on the prop for the same throttle position at lower speeds - within reason - can/may increase fuel efficiency... I can just as validly make the arguement that with the 'normal' prop the engine is underloaded at lower speed as one can make the arguement that by increasing the pitch the engine is overloaded... The best method of loading a diesel (or any engine) is with a variable pitch prop and and EGT gauge... For every throttle position there is an optimum prop pitch... This optimum pitch changes with changing rpm, changing hull speed, changing temperature, changing barometric pressure, changing humidity, all of which change the engines power output at that moment... The reality is that the fixed pitch prop on a boat is correct at only one combination of boat weight, speed, power and RPM... Luckily for us the engine is happy over a broad range of rpm/power loadings so that the majority of us don't even notice that the engine is mildly over or under loaded... It is likely that with a variable propellor and an EGT gauge that one might decrease fuel burn by up to 10% at lower speeds simply by optimally loading the engine... denny Everyone is raving about the all-new Yahoo! Mail.