Hi l have a Yamaha v6 outdrive and l want a better prop. l have a 3 blade on right now that 5000 RPM l can hit 40 MPH but l want more speed. What is bettera 3 blade or a 4 blade prop and how does the pitch effect your speed.

well 1st that sounds pretty good to me
but you need to give more info
1st engine hp
2nd rpms at w.o.t.
3rd what is the pitch and diameter your turning now
than l can tell you better
but if the rpms are at where there supposed to be at w.o.t. than the only thing l suggest is to turn a s.s.prop no flex there

More than likely the RPM range u want to be at is 5400 to 5600 at WOT(wide open throttle). Instead of relying on us, l would find a local prop shop that reconditions props. Take ur prop in there & tell them what RPM u r seeing at WOT. l can tell u right now that ur prop is either too large in diameter, or is too high in pitch by about two inches. If u continue to run that prop u will wear out ur engine quicker because it has too much of a load on it. l bet it plane is off pretty slow too. You will see a much better hole-shot with a smaller prop.

This is all assuming ur engine is running properly!

A 3 blade aluminum will give u higher top end, while a 4 blade will.give u more acceleration out of the hole. 4 blades(or 5) r mostly used on boats that pull or carry a load, such as a ski boat or work boat. Have ur motor tuned up, & see if there is a difference in rpm. 5000 rpm is a little low for a V6, by about 400 rpm, but not a big issue. Make sure ur bottom is clean, if not, haul the boat, use hull wash & a stiff bristle brush to clean the bottom, & then wax the bottom with a marine hull wax. This might give u a couple of mph. l dont recomend stainless props on anything but performance boats, the cost of the prop is too great for for the small increase in speed.

What is your WOT throttle range according to Yamaha?

Are you in the range?

Yes, then there is not much else to do.

Four-blade props will improve the hole-shot, and reduce the top end. This is not your option.

How about a stainless prop? Eek out another 1 to 2 mph.