I have a question for our resident propeller wizards. From time to time I see people mentioning they've had their propellers repitched. Although I've probably had dozens blueprinted (occaisionally blade pitch matched if cast poorly), I've never gotten into this mod. So I have a few questions.
Can a propeller be repitched (example 30" to 32") and perform as well as one that is already cast and blueprinted at the same pitch (32")? I realize there are limits to resizing. How much pitch change is practical?
If you're trying to build a 31" pitch prop, are you better off with a 30" and pitching up, or a 32" pitching down?
Thanks in advance for your input.
Steve

Propellers can be repitched. We don't like to go further than a inch or maybe two at the most. Any given family of propellers has a certain built in geometry from the amount of blade area to the cord length , diameter, pitch progression, cup heights and locations, etc. Repitching changes the true engineered geomerty because the blade root is stationary. Therefore to really repitch a propeller and keep it identical to its design, the blade would need to be removed and rewelded. Obviously this isn't a good option.

I have found true pitched casting to out perform repitched castings the major majority of the time.

As far as going up or down with a casting is concerned. To BBLADES, it depends on the family of castings you are using. You need to know the intimate personalities of the certain propeller and the application you are working with. We will depitch on some very efficiant applications to gain a beter speed result or up pitch in other applications that may benefit from the lower angle of attack.

Great question. Your best to consult your propeller shop and check their experience. Blueprinting and Lab Finishing are great ways to change rpm levels. Especially when looking to increase the R's

Brett

Brett,
Thanks for your precise answer. I find your information very helpful. Although we haven't done business, I have some friends who have work done by you (Eric Smith/etc.) and are pleased.
The reason I'm asking is I've added power over the winter, and I am redialing in my setup. My former best all around prop (Hydromotive 28" P5-X) seems to still be working very well, just at higher RPMs (+500 from the old setup).
It's currently running 90 to 93 @ 5800 to 6000 depending on load and conditions. I borrowed a Merc lab 32" (which I am considering buying) from a friend and turned it 94.5 @ 5700, with a very light load. I'm thinking this prop can be further worked to suit my setup (a little less pitch, a little more cup?).
The boat is a 28' Nordic Heat single step with a modified Merc 575 putting out an estimated 800 propshaft HP. X dimension is high @ 19 1/4". Currently running a 1" spacer and IMCO lower. Boat handles great with both props, but seems to prefer the 5 blade, probably because of the high XD.
I'm still testing props, and will be trying a 30" B-1, and a 29" HydroP5-X (both blueprinted).
What I would like to do is keep the speed (of course ) and keep my rpms in the 5700/5800 range.
Regards,
Steve
PS I am a former outboard drag racer, and met your mentor Dennis at Lake X back in the winter of 1991, when Mercury was holding their Pro Max development meetings. He was a great guy and I enjoyed spending some time with him. Wish I could have spent more time discussing propellers. He was the man.

Steve, do like I did and spend $1700 and slow down and gain RPM.....then get a set of beat up used props for half price and haul azz! Another one of my typical money spending no result success story.

John,
Looks like you're running pretty well to me !
Hey, what are you doing for Memorial Day? A bunch of us are headed to Dale. Why don't you go with us?
Steve

Steve,

Thanks for the comment on Dennis. It's always good to hear old stories about him. I still feel like he is with us. He left too early. Live every day to the fullest cause you just don't know.

A tweaked 30 B1 may just be the prop for top end and a 5 blade for daily cruising.

Bret

I think we are going to the hill for one day and then one day on old stumpy. I still dont have my interior done....so I will have the red neck thing going on as usual......no engine hatch! Are you guys going to be up there all three days?

John,
For all four ! Getting out of here 10:00ish Friday AM.
We'll be back.............well Monday sometime.
Come up and see us if you change your mind. You don't need need no stinkin' interior ...........
Regards,
Steve