I have a GD 35 SD running a 11 x 12 3-blade pushing a 17ft xpress duck boat and 50ish hrs on the motor. i hear alot of talk about prop wear affecting performance. This is my first mud motor and have no idea when to do what. How do you properly measure a prop? Stupid question I know but just want to make sure I'm doing everything right. Thanks for any input.

A new go devil prop has a good bit of cup on the blades and the edges are dull.

Do you have any cup left on the blades and are the tips of the blade sharp?

Have you noticed your speeds dropping?

I have noticed it doesnt plane out as fast and I measured from the tip of one blade to the tip of another and got 10.3 in. Mortor had 40hrs on it when i bought it seemed like it got on plane fatser than it does now especially under load. There is some cup left towards the center of the blades but not so mmuch at the tip. i just dont know what the 11 or 12 in the 11x12 description are reffering to. 12 is the cup I think and 11 should be the diameter right?

I just measured from the tip if the blade to the center of the shaft. I got 5 3/4 on a newer prop with no wear.

I measure across the blade - new they are 3 1/2" wide - at anything under 3 1/4"
the speed and mud digging power is noticably reduced - at 3 1/8" I hang it on the wall....

With our sandy mud 50 to 70 hours is about the average life of a prop for me....

RPM is also a good way to judge - I turm about 3600 rpm new - about 3800 rpm
when they are between 3 1/2" and 3 1/4" and running in their prime - then when
they turn over 4000 rpm they are worn out ---- these #s are with a stock engine
and with mods you would turn more rpm - but the point is they go up noticably with wear...

Thank you for info. thats exactly what I needed to know.