I need help with prop sizing???

[moparlulu]

Long time lurker first time poster here. I'm putting a 18' flat together and I'm wondering what I should get for a prop. It has a top loader box with 1.14 ratio Its going to have a dynoed 650 hp ,600 ft.lbs. of torque mopar for power. No more than 65 to 6600 rpm. I'm going to be using it for pulling a knee board and ripping around the lake. Also can a top loader turn right or left as far as rotation goes??? Any help at all would be great. Thanks, lulu

[RiverRacer]

What kind of boat do you have???? lot a variables here, but with that kind of power I hope you plan on putting a stop at half throttle!. The v-drive don't have anything to do with turning any direction, prop rotation does but it will turn both direction regardless of prop rotation, just better to whatever the rotation is but in a ski boat it don't matter either way will work!..

[moparlulu]

I'm not sure of the mfg of the hull, all I got was a bill of sale with it. It looks close to a eliminator hull. Half throttle???? Whats that??? I didn't know if the box gears were cut for clockwise or counterclockwise rotation or if it made a difference

[gfinishline]

In your case the CLUTCH is the factor in rotation. Pulling Knee boards is best done with 3 blade props. "Ripping around the lake", is best done with a 2 blade prop. NO! One prop will not do both with the same quality of service! The hull design and shaft angle will lead us to a more accurate diagnoses of your question.

[moparlulu]

Well I know the box has 10* stamped on it if that helps any. I want to thank you guys for the help so far!!! I came from a wheeled drag racing background / forum and if you weren't in their little click, you didn't get much help! Thanks again.

[RiverRacer]

You mentioned a "Top Loader", if indeed you have one it is 12 degree not 10, your shaft angle will be 10 though!.. Don't worry no click here, don't think there is a description for this crowd that resides here, LOL...:D:D:D

[George1301]

Don't let out all our secretes..!
Engine facing forward or to the rear would be my first question..?
Welcome to the greatest bunch of folk this side of the delta...!

Geo

[moparlulu]

RiverRacer, your right, I said its was marked on the box but The 10* is on the prop shaft brg housing,so i took it it the box would be 10* also. George 1301 If the box can turn either direction I'd like to mount the motor facing the rear. I'll get a couple pics of the hull tomorrow and post them, maybe you guys will know what it is.

[RiverRacer]

You can run it either direction it don't matter!..

[gfinishline]

Those old "two dog clutches" are directional. The two pins/dogs have ground in 'ramps' on them and so does the receiver in the lower shaft. Just as the new style "3 dogs (ramps)" have direction, those old clutches will "pop out" of gear if turned the wrong way. I would inspect the clutch before using it in any direction! It may be unusable at this point, due to wear. The only "old style clutch" that I remember as being 'omnidirectional' was the old "spline drive clutch", and was not shiftable.

[RiverRacer]

Or the old 2 pin deals that look like dowels that go into a receiver, they work either way!..

[gfinishline]

Art, I don't think the receiver in the lower shaft had the "ramp" angle in both directions. I think they were 'finished for direction, just before heat treat". "Where is that Mitch guy?"

[RiverRacer]

Art, I don't think the receiver in the lower shaft had the "ramp" angle in both directions. I think they were 'finished for direction, just before heat treat". "Where is that Mitch guy?"

George, remember the old style with two round deals about 1/2" round 1/2" long top and bottom and just went into a slot, completely different than the 2 and 3 dog deal no ramp and would work in either direction!..