Re: What pitch prop do I need for my 25hp Yamaha
I should have asked before;what are you trying to do?
Wouldn't hurt to at least know your speed.Maybe you could borrow a GPS.How did it perform with the 11 1/4 prop.
Going from aluminum to stainless will usually reduce rpm.but can push better.Increasing pitch reduces rpm and power can go faster if the motor can spin it yours can't..So you did a double whammy.
First you should put the 11 1/4 back on and at least get your speed. Check the motor height.Starting point the antivent plate should be even with the bottom of the boat.Raise the motor about 1/4" at a time till just before venting becomes a problem.Use 1/4" sticks to support.just be sure it pumps water and the clamps have a good grip.Under ideal conditions an inch can gain 2 to 3 mph.Also carefully adjust trim as each stick is added.Improving speed can also improve mileage,may help handling and hole shot.
To get back to the "crap shoot".Without your max rpm and speed We don't know if the motor is within its proper rpm range.operating outside the range
can lead to premature motor failure and inefficient operation.
You may be able to borrow a shop tach or buy a Tiny Tach,reasonable price and easy install can be used on any similar motor without regard to stator poles.
I would say the factory would figure that motor to be pushing boats very similar to yours And I'll bet if there is a standard prop it is the 11 1/4.
If I was going to crap shoot a prop it would be an 11 1/4 stainless.
Keep in mind the best trim(not height) for speed is not the best for hole shot.
Under ideal conditions your motor should be in the 28-30 mph range.
Factory speed specs are based on a light fast boat ideally setup.
