how to keep prop hooked up

[anthony_marquart]

I am not happy with the way my rigger comes unhooked over wakes. What are design points that help keep a rigger hooked up?

I can add a little weight to the transom.,,, I'm thinking my center ski is too wide... CG is back like a JAE... boat too long making the transom weight too light?

 

[RodneyPierce]

Im thinking this is just a habbit of the ski boats. I could be wrong though.

 

[LarryConrad]

Bigger diameter prop.

 

[Tim Kish]

Try adding some cup to the prop to take some lift away.

Tim K

 

[shoboat]

Tony,

I am with Larry, bigger diameter propeller and more rearward CG.

Strut weight is more critical than you think. Cupping the propeller

too much just kills the RPM in the engine. The ski may need some

modification or possibly more refinement. This is a very interesting

topic since one of my customers shared a story about his JAE-21.

He is running very well with a very large diameter propeller with a

fair amount of cup and reduced blade area.

Thanks,

Mark Sholund

 

[Tim Kish]

Cupping a prop is no different than tuning a pipe to the motor.

To be done properly it has to be done at the pond a little at a time , every boat is different.

Adding a larger prop may work but that can also kill rpm with added pitch and dia. , you also change the A.O A. and if the strut is fixed like the JAE it could kill speed as well.

Interesting topic for sure with lots of variables.

Tim K

 

[Tim Kish]

I think that at the speeds the 21 hydros are running it would be almost impossible to keep them hooked up all the time , just hope it lands flat and keeps going lol.

Tim K

 

[anthony_marquart]

Yeah,.. I've been thinking I may need more diameter. I'm also going to make sure the strut is dead flat.

 

[shoboat]

Tony,

To tell you the truth, the C.O.B. pitch has a lot to do with

how well the boat will run on any given propeller. The diameter

when it is correct will help your boat more than you think.

Take Care,

Mark Sholund

 

[anthony_marquart]

1450, reduced a bit.. don't have the prop in front of me right now to look... but yes, a .20 boat... I have thought about those winglets too... may try that.

 

[Tom Foley]

Put a 1/2 ounce stick on weight near the transom and flatten the strut as others have said . Easy try and might yield some info . Mark sholund makes killer 21 hydro props btw .

 

[anthony_marquart]

Yeah,.. mark does really god props. .. I'm running his props now. I"m running a flat bottom strut,.. I like the water shearing action of it.. but maybe I need a round one to let it settle down a bit... Gonna try the added weight too.

 

[dwilfong]

I built my own rigger from the KEPS plans and added the ski on it. the boat dose come unhooked in some water with the ski.

I liked the way it ran with rear sponsons better but it will run a bigger prop with the ski.

Found that with the ski you need to take some of the lift out of the prop to keep the back end in the water. the ski will do most of the lifting. the best prop I have found is a H7 with a back cut from tip to hub at 17deg. this will take the lift out of it. but you will have to edge cup and tip cup to get the water to stay on the prop longer.

Gust what I have found.

David