prop material vs pitch

[stubblejumper]

Once I find the correct aluminum prop for my 75hp mercury four stroke engine,I plan to buy a stainless prop,and keep the aluminum as a spare.The Mercury prop selector chart recommends the same pitch for both stainless and aluminum,yet some people are telling me that since a stainless prop flexes less,the effective pitch will be greater.They say that to compensate for this,I should get the stainless prop with less rated pitch.What are your thoughts on this?

 

[Silvertip]

Re: prop material vs pitch

There is no positive answer to your question. That's why testing, always with as close to the same conditions of load and water conditions as possible is so important when making a prop purchase. Prop recommendations get you into the ball park but may not be the best for your boat & engine. Work with a reputable prop shop or dealer that will let you test several models of stainless props of various pitches to get the best performance. Don't forget to work with engine height (mounting height -- not trim) to optimize the setup. What is more important than worrying about the difference between stainless and aluminum is the difference in performance because of prop design. Just because you have a 19P aluminum for example from vendor "A", does not mean a stainless 19P prop from vendor "B" will perform the same or better. It may actually perform worse. You would be better off looking for a stainless first and then buy the aluminum spare since it will be used in emergencies or if someone steals your stainless.