prop questions

I like to wakeboard, so I've heard a 4-blade would be better for these lower speeds.

What diameter and pitch 4-blade would be equivilent to my original 13X13? (of course I don't want to lose top speed either.    

bc, OOPS! My large mistake! Thanks for picking that up and my apologies for stating it wrong. You are correct in your thinking as it should have read, "DECREASE engine speed...". I can't even quote from a book correctly. Sorry for any wasted mental time and confusion that caused.
   

ReidP
Remember that the 123 transmissions and v drives run under and overdrives so you can toss the handbook. Now with that being said the HP being told to you in Ski boat are not actuall. The association lets them advertise between 20 to 30 % more. The book is fine on general nomenglature of propellors, and on 1.1 situations. The underdrives give you more built in torque and overdrives take away the torque and need lots of power, thats why the differential in RPM and speed. You have to add or subtract to get the prop speed.

That seems odd. With an increase in pitch you would be grapping more water and trying to push it back. It seems that, that would but a heavier load on the engine and slow down the rpm. It makes sence that the speed of the boat would increase but not rpm. In my particular case I'll be able to spin up to 5500 rpm and most likely use a 15" pitch prop to bring it down to around 5200 rpm.

The propeller book I spoke of earlier is:
"THE PROPELLER HANDBOOK - The Complete Reference for Choosing, Installing, and Understanding Boat Propellers", by Dave Gerr, published by International Marine and McGraw-Hill. It can be ordered from 800-262-4729.

In regards to the 300 rpm per inch of pitch question, pg 45 covers a handfull of the "countless rules of thumb floating around about propellers", and actually talks about a "two-inch increase in pitch will increase engine speed 450 rpm"??, and doesn't say it's true or fact. That's only 225 rpm per inch so go figure, especially compared to Jeff's actual 400 rpm drop with +1". And I agree with Jeff's position that with a 240-260 HP 351, 4800 was a bit high for that engine's power curve, which could explain why it lost no speed. A Pro-Boss or GT-40 351 typically turns upwards of 4700-5000 at WOT from what I've seen, and speeds probably benefit from the increased rpm in those engines with the enhanced performance components.

The term I missed earlier when pondering the OJ props vs Federal props was RAKE, "when the blades lean either forward or aft, when viewed from the side." With the case of the OJ's I've got, they slope aft which is positive rake, and "the raked blades have more length and thus more area than vertical blades of the same diameter." So this make sense I guess as to why a raked 12x13 OJ turned the same rpm as my 12x14 Federal, mostly vertical blade prop. So much to learn.      

BC,
I didn't get that specifically from the book yet, but will check. Everything I'd ever heard though, did lean towards the 300 rpm, and from personal experience I've seen that hold somewhat true when comparing same brand props.

My humble opinion says pick up a good 13x13 Michingan/Federal like Woody says was originally spec'd. Then you can be CCF test-bed for a 13x13 vs 12x15 "on a Nautique" comparison. I only say the Federal since it was originally spec'd and there are still tons of them on older boats like yours/ours. Plus I very recently picked up an excellent book on Propellers, (just listen to the sound as I open up this thought provoking can of worms), and every 13x13 design is not the same in terms of blade shape and angle. There is detail on this in the book, plus I've learned first hand after purchasing a new 12x14 OJ to complement a 12x14 Fed and not understanding why I lost 300 rpm. The OJ props for me have performed just great, once I figured out the comparitive size issue, but unfortunately no faster or slower, on my boat(s) anyway. Anyone else have prop results to post? I'll send another posting this evening once I've got the book in hand with info on it if anyone's interested.

Thanks for all the help!

My current prop (was on there when I bought the boat last year) is a 12X15 cupped. It seems to perform great, but then I've never tried any other size. It's smooth and strong out of the hole, and has a top speed of 52mph (WITH OR WITHOUT people and gear).

I like the idea of buying a new (or reconditioned) prop to use while I send mine to the shop for reconditioning. Now I just need to decide which one to buy.

I guess maybe I should buy the original size (13X13 - thanks woodyelc).

- I don't want my broth-in-law's new I/O V6 to EVER STAND A CHANCE of outrunning me!

Yeah, probably. But I'm confident you meant that they historically have rated it way, way too low. Correct Craft wasn't crazy all these years. But WHAT does this have to do with props and Woody, other than the fact that Woody KNOWS Ford horsepower, and nothing spins a prop faster than the blue oval.

Bill,
Is that SECC's Woody? Like there's another?

BOAT CAME WITH A 13X13X1RH FEDERAL PROP FROM CORRECT CRAFT. HARD TO TELL WHAT IS ON YOUR BOAT NOW.

Take the haul number and ask correct craft. a 79 351W was 240hp

Give the folks at Michigan Wheel Corp a call. http://www.miwheel.com/. Federal Propellers is one of their companies. Federal was the prop which came originally on my 89 2001. They have a web site where you can plug in numbers on your boat, engine, xmsn, current prop, and current performance. Give them about 10 days this time of year and they can match a prop to your boat.   

used props

he has an exstensive list of left hand stuff.

nauti girl.the delta propeller co 877-238-8214 .talk to them about the damage to your prop/price they been around for years.
always done great work for me at the right price.
www.deltaprop.com