prop slip questions

[Darrylb]

What is acceptable or the norm for prop slip?:confused: :)

[ncst8er]

Per John Tiger in his articles, anywhere from 4-10% is normal for a good setup.

[Raceman]

I think you'll find VERY few props that slip 4%. 10 seems to be a pretty good average, although there are a lot of variables.

[Techno]

A good biting prop of a round ear on a tunnel maybe 4% To over 14% for a high pitched cleaver on the same boat moving at a vastly higher speed.
The slip is relative to the prop your running on that particular boat/setup. You could reduce slip but this may reduce top speed too so it isn't the goal it may seem.
Mostly it isn't the prop that determines slip but the hull and speed. The exception to this is the cleaver. I've crunched alot of comparisions and cleavers slip alot, they also produce a better speed when they can be used.

If you see one of those multiple prop tests try picking a few and crunch the numbers. The values are almost meaningless. Same prop with a different pitch has a different value. Value meaning ability to compare it in a prop calculator.
.
It can't be computed with any accuracy. Props are inherently stamped wrong too. One 26 and another 28 could both be wrong and both be a 27"
Put a different way a high slip value could actually be a smaller prop pitch. This put into the calculations throws everything off.
Even better you could get 0% or - % slip because the pitch was wrong!
Makers actuall skew the pitch so thier prop is "stronger" or "faster" than a competiters. Then if they were worked on they no longer are the pitch stated.

So to be of any value you need accurate speed, Tach and pitch. Speed is easy Tach isn't too difficult but pitch could vary along the blade so even if measured would require a few calculations to cover the spread.

[Darrylb]

To reduce slip numbers what do you have to change in your setup? I have a 30 cleaver that runs 72 gps @ 6000 motor gearcase is centerline with pad....Thanks for info Darryl

[Techno]

I think thats 20% which is bad!
You probably don't need or want a cleaver on your boat, its a stern lifting prop and you need a bow lifting prop. Thats the first thing to do is get a chopper. Your cleaver isn't a wash since you can sell or trade it.
The prop height and amount of set back both tweak it.
You should be doing low to high 80s depending on the gear ratio. I keep forgetting what the standard one is. 10% slip.

Probably the best bet is to post a new post with your setup and your boat. There should be enough others with almost the same thing and can get you what they use and have setup. A done guide that you can start from and have little tweaking to do.

Engine, prop, prop hieght from bottom of boat, boat, setback amount if any.

Mostly though I think its the prop.

[Darrylb]

I have a volero v bottom 5.5 cmc hydrolic jack, 1.80 gear est hp 200 yammy, Bobs nosecone gearcase centerline level with pad... The reason I have the cleaver its really bow flighty and likes to walk worse and hard to drive with chopper, the chopper I have is a 30 also and runs a hair slower than the cleaver...also have a 30 hoss triton which is slower also. I am messing with balance of boat wich has helped slightly. to me the boat either seems to be in the water too much, or too high cant get it to level out. As soon as I start to level the bow drops into the water . Its just plain flighty and Im not sure if this is the way they run as this is my first boat with any power....and thanks for the info Darryl

[MTCM]

Darryl,

Find a stock unmodified gearcase and put it on there. Find a good 14 1/2 x 28 Chopper. The Jackplate is OK, it can stay. Once you get the stock case on there, adjust your Jackplate (up) just til the engine temp starts to rise then bump it back down slightly til cool. Keep the engine trimmed level. I have run V-Kings at 82+ mph @ 6000 rpm with stock 175 Mercs this way.

IMHO the nosecone is raising the stern and dropping the bow. The cleaver is also aggravating the stern lift further dropping the bow. With a dropped bow your slip goes up.

If you want that thing to fly you are going to have to learn how to keep it up on the pad. It takes practice to do this. Many V-bottoms require continual small steering corrections to hold it level and in a straight line. Your squirelliness is being caused by the prop torque which is driving the boat off the pad to one side. You have to be able to anticipate when this happens and apply the small steering corrections. There are many V-bottoms that experience this longitudinal instability. The better designed bottoms offset the onset of instability by spilling air from tunnels and strakes opposite of the instability (A-Boats) so fast that the hull never gets squirrelly. In other words you never know it happened. Take care.

[Techno]

Check out this movie
V-king at 102 MPH (http://www.screamandfly.com/screamandfly/images/Photogallery/Video/viking.mpg)

Or the page
Video (http://www.screamandfly.com/screamandfly/video.htm)

You may be trying to go too flat.
If nothing else its worth watching.

And of course the usual solid mounts dual cable steering and foot throttle requirements.

[Raceman]

I can't imagine a cleaver slippin' 20+% unless you're seeing it out the back of the boat. (big rooster tail) My experience with the cleavers has always been that they'd run higher than other blades before they turn loose. Are you sure your tach's right?

[MTCM]

He would definitely see a tail...........................

I feel like that cone is not quite right. May be on there wrong or the hull don't like it.

[Darrylb]

Thats what I was thinking was maybe tack is off, I will try and hook up a digitron to verify as for nosecone I sure hate to take off it was put on by someone reputable so I know it is right and as for seeing it out the back probably 4 to 6 ft rooster. I will look for a 28 chopper to try. Thanks for the info and any replies. Darryl