20 hydro props

[shoboat]

Steve P,

No that is not it.

Call me if you want to know more.

I am swamped with work to type an essay on the subject.

It is very easy once you understand the set up.

Thanks,

Mark Sholund

231-590-3023

 

[shoboat]

Guys,

Most propellers will run at .7 radii once they come up to speed.

This is where your boat will run and this is what determines your angle of attack on your Hydro.

Now if you mark this reference point on your propeller it will be 70% out from the hub on the trailing

edge of the propeller. Now if you put on a bigger blade diameter you will need to measure the difference

in the 70% T.E. mark on each propeller. Then you will have to raise your strut up the difference between

both 70% marks on the T.E. this will be your new strut height with the bigger propeller. Say your .7 is 1"

on a 1445 and now you want to run a 1450 with a .7 of 1.25". You will have to raise your strut up .25"

To keep the same angle of attack with the bigger propeller. Pretty easy or not?

Call me if you still don't understand 231-590-3023 between 6AM and 9PM E.S.T.

Thanks,

Mark Sholund

 

[Andy Brown]

Guys,

Most propellers will run at .7 radii once they come up to speed.

This is where your boat will run and this is what determines your angle of attack on your Hydro.

Now if you mark this reference point on your propeller it will be 70% out from the hub on the trailing

edge of the propeller. Now if you put on a bigger blade diameter you will need to measure the difference

in the 70% T.E. mark on each propeller. Then you will have to raise your strut up the difference between

both 70% marks on the T.E. this will be your new strut height with the bigger propeller. Say your .7 is 1"

on a 1445 and now you want to run a 1450 with a .7 of 1.25". You will have to raise your strut up .25"

To keep the same angle of attack with the bigger propeller. Pretty easy or not?

Call me if you still don't understand 231-590-3023 between 6AM and 9PM E.S.T.

Thanks,

Mark Sholund

What you are saying is that most props want to run on the outer 70% of the radius. That is not fact. Some yes, but not "most".

 

[shoboat]

Andy,

I am saying that most propeller designs that we use for our Hydros

run on the last 30% of the tip of the blade.

There is no outer 70% of the radius.

Greg,

The middle picture looks pretty close to the last 30% in the water.

Thanks,

Mark Sholund

 

[Ian Inverarity]

Let us know how that goes Greg. I cant try that without modifying my strut, I dont have that much adjustment!

 

[ozbryan]

Andy,

I am saying that most propeller designs that we use for our Hydros

run on the last 30% of the tip of the blade.

There is no outer 70% of the radius.

Greg,

The middle picture looks pretty close to the last 30% in the water.

Thanks,

Mark Sholund

Are you measuring from the center of the hub? Or from where the blade joins the hub?

Interesting topic.

Greg great photos!!

 

[shoboat]

Greg,

The trailing edge of the propeller is broken down into

10 different radii points. The first one is after the hub

and the tip is 1.0 so we do most of our cupping at .7

radii. When I get home from work I will take some

Measurements and then post them for you. We should

Really move this to a strut and boat height set up thread.

Thanks,

Mark Sholund

 

[moparbarn]

Greg,

The trailing edge of the propeller is broken down into

10 different radii points. The first one is after the hub

and the tip is 1.0 so we do most of our cupping at .7

radii. When I get home from work I will take some

Measurements and then post them for you. We should

Really move this to a strut and boat height set up thread.

Thanks,

Mark Sholund

great topic for the how to forum, mark. thanx for sharing your knowledge - again

 

[anthony_marquart]

So,.. what we are saying here is basically that if you run a larger diameter prop, you have to raise your strut or you will decrease your AOA. The 70 / 30 ratio may very for people,.. but I think this is the thought..

 

[RodneyPierce]

So,.. what we are saying here is basically that if you run a larger diameter prop, you have to raise your strut or you will decrease your AOA. The 70 / 30 ratio may very for people,.. but I think this is the thought..

Tony, Im thinking more along the lines of raise the strut to run a big prop otherwise its going to overload the motor, and never stage...

 

[Steve P]

I think I understand what Mark is saying. The .7 measurement is not for inital setup, you still need to figure out strut angle and depth based on your motor hull combo by trial and error or someone else advice. But once you figure it out this is a guide line to how much strut adjustment to make to pevent over or under loading the motor with a new porp you want to try.

Mark is this close?

 

[Andy Brown]

Andy,

I am saying that most propeller designs that we use for our Hydros

run on the last 30% of the tip of the blade.

There is no outer 70% of the radius.

Greg,

The middle picture looks pretty close to the last 30% in the water.

Thanks,

Mark Sholund

"The middle picture looks pretty close to the last 30% in the water."

:lol: :lol:

What about the 1st pic where the blade is running full depth?? I guess the boat is runnig at a bad attitude there Huh?

Take enough photos of a bouncing boat and you can find just the prop depth you want.

 

[anthony_marquart]

So,.. what we are saying here is basically that if you run a larger diameter prop, you have to raise your strut or you will decrease your AOA. The 70 / 30 ratio may very for people,.. but I think this is the thought..

Tony, Im thinking more along the lines of raise the strut to run a big prop otherwise its going to overload the motor, and never stage...

I think we are talking the same things.. Low AOA, too much prop in the water.. same results... slower boat!

 

[RodneyPierce]

So,.. what we are saying here is basically that if you run a larger diameter prop, you have to raise your strut or you will decrease your AOA. The 70 / 30 ratio may very for people,.. but I think this is the thought..

Tony, Im thinking more along the lines of raise the strut to run a big prop otherwise its going to overload the motor, and never stage...

I think we are talking the same things.. Low AOA, too much prop in the water.. same results... slower boat!

Technically, the chance of it lowering the AOA would be slim to none if the motor/boat/strut height cant pull the prop. It wont ever get on plane. Therefore wouldnt lower the AOA at ride.

 

[anthony_marquart]

well,.. I sure don't want to disagree,.. but if you were running a prop with a larger diameter, and less pitch,. I think this could happen.. but,.. who knows. I think we're splitting hairs on this one.. it's possible to have the rear of the boat ride higher with a bigger diameter prop, less pitch the motor would still hook up.

 

[RodneyPierce]

well,.. I sure don't want to disagree,.. but if you were running a prop with a larger diameter, and less pitch,. I think this could happen.. but,.. who knows. I think we're splitting hairs on this one.. it's possible to have the rear of the boat ride higher with a bigger diameter prop, less pitch the motor would still hook up.

 

[aaron alberico]

So what do you think is going to run faster?

Big dia less pitch or small dia more pitch????

 

[Ian Inverarity]

Are we talking LE pitch?

 

[anthony_marquart]

the million dollar question!! I guess that would depend on your boat / motor / pipe/ setup.

 

[RodneyPierce]

So what do you think is going to run faster?

Big dia less pitch or small dia more pitch????

both