Identify prop?

[Carl1969]

The propeller on my 25hp Evinrude 2-smoker is only marked with 4 dots arranged in a square. I'd like to buy a spare prop, but I'm seeing pitches from 10-15 listed & no idea what I have. Not necessarily looking to change pitch as the boat runs good & without a tach, wouldn't have any idea whether the motor was running in its happy spot.

Any advantage to a 4-blade prop?

[snagged in outlet 3]

@fishinwrenchmight be able to help.  

[fishinwrench]

There should be a part# on it somewhere.   You may have to remove the prop to find it.  

As to the 4-blade question.... No.