I just plugged in all the info you say is accurate leaving out the HP number and got their answer. In figuring the constant I would assume you would be more like 215, based on a slip factor that is slightly higher than they state at 225. But that would just push the HP even higher.

One can play with the toy and make it go off in any number of different directions depending on what one feeds it as fact, or one can come up with facts based on what is fed in, it's a fun toy. Just for grins I just threw you and the Mrs. out of your boat at WOT, and it's going 2 mph faster without you in it. My pencil just broke so I'm going to give up.

don't forget the wieght of fuel, gear, and persons (use real world floating wieght in your calcs guys)

there is no way you are at 6% slip on a v-bottom Peter.

The pitch "number" stamped on 'em means little or nothing. This is definitely skewing your numbers. Lots more variables across the blade. Having them "layed-out" (machinist's term) or rather propscanned which is very similar to layout is the most accurate representation of what you've really got.

The reference to the right hand side of the chart you are refering too "Optimum Slip Percent (For max top speed)" is just for reference use. It is not gospel. Nor is the calcutator.

Garbage in garbage out. Use the facts.

Dave

I'm sure you have the same formula I've got, the old pencil one I got years ago from ML, a theory based on a propeller screwing itself thru a solid material, which all things being equal would mean we could walk on water. I did not say as fact that my slip is 6%, Axa's computer said that based on the fact his GPS said my all season best was 81.7 (not mind you .6 or .8), combined with my tach says 5300 and my Hydros are stamped 26's, all theory, be it computer generated or done with a pencil. All I've ever said is that I "think" my boat runs 80 + on a good day, in contrast to Axa who thru technology "knows" his runs 87.7 with his 29.1" pitch props.

Ok. Just did. 9600lb + you & the mrs. + some fuel @ 10500lb, your 242 constant, your 87.7 gps speed......= 1379hp./689.5 per side. This works ? Throw in the 500lb of stuff you say the mrs. packs in the cabin and your hp goes to 1445hp/ 722.5 per side. This works better ?

did you guys read the prop tech info in PRA mag last mo?

Prop slip means nothing, just stuff for people to argue about.

No, but I agree. Which is why I use my antiquated speedo/ water pressure device if trying other props. My theory has always been that if the needle went higher, I likely was going faster, and if it did not go as high, then I was most likely was going slower. Works for me, but I'm real low tech. I often lick my finger and raise it over my head to determine wind direction as well, that works with remarkable accuracy as long as you can be content with "thattaway" for an answer. I ran my index finger thru a table saw years ago and since then it's not been the same.

but it still holds true that unless you've measured the blade over the breadth and length of the blade, compared, and each blades relationship to the hub...you don't what it is.

The boat was empty and on 1/4 tank of fuel the day of the Fun Run...9600 lbs. With us.

Dave

Yes, I agree. However the added .07396 of pitch, you added in, will change the computer results, will it not ? ( added for clarity, not to offend ). Well all I know with absolute certanity about mine is that all 4 blades are in fact attached to the hub. I determined that by looking. (wink-wink) I gotta figure out how to get them down here, can get them up there, but not down here. (me dumb - unhappy)