So You Want To Go Faster?

[shoboat]

Boaters,

Like the title says "so you want to go faster?"

What is it going to take: More cup? More pitch? More diameter? More RPM?

How about just a little more leading edge pitch on your same propellers?

More pitch and more RPM will do the trick for sure. Some have tried to modify

their engine and it still won't go much faster. Could it be just .050" change to the

Leading edge of your current propellers? What have you been doing to your propellers

to make them run better? Any good results you want to share? I have some, but lets

Look at what you are doing? Some propeller discussion to learn from. Please add what

works for you.

Just A Few Things To Explore At The Pond,

Mark Sholund

 

[RodneyPierce]

Props are sort of a "black art". Just takes a lot of time, tweaking, cutting and sharpening to learn the ropes. Starting to get there myself, but it takes some time for sure!!

 

[dwilfong]

The thing with props is no two set ups are the same.

If you are running a conservative setup with little or no mods to the eng. There are good parameters to go by that have bin tested over and over.

As you go to the edge of what has bin done it gets harder to find the balance of every thing that a prop dose to a boat and the eng.

I always remember a article on how the leading edge is the governor on a prop.

then there was a reference to the back side of the prop is the true leading edge that was tossed out there.

Think about it the front of the prop has to travel thew the on coming water. It acts like a brake.

If the back side has less than the front tan the water is pushed around the out side of the prop.

There was a video posted of a surface prop running and you can See the prop pushing the water around the front of the prop.

Their are those that can see this in their mind and under stand how a prop goes thew the water.

The numbers are not the whole story to a prop but how it flies thew the water is the key.

I was told that a high pitch prop will lift the back of the boat as you let of the throttle.

I have found this to be very true with a big prop going a high speed in my hydro.

The prop will push the back of the boat where it wants not where you want it to go.

It has put me in some bad situation lately that I have bin fighting with.

In a play boat or a record trials boat this is not a problem. But in a heat racing boat it is not desirable.

Speed comes with its down falls. But still I would rather be fast and contend with it than be slower.

 

[julianconde]

The thing with props is no two set ups are the same.

If you are running a conservative setup with little or no mods to the eng. There are good parameters to go by that have bin tested over and over.

As you go to the edge of what has bin done it gets harder to find the balance of every thing that a prop dose to a boat and the eng.

I always remember a article on how the leading edge is the governor on a prop.

then there was a reference to the back side of the prop is the true leading edge that was tossed out there.

Think about it the front of the prop has to travel thew the on coming water. It acts like a brake.

If the back side has more than the front tan the water is pushed around the out side of the prop.

There was a video posted of a surface prop running and you can See the prop pushing the water around the front of the prop.

Their are those that can see this in their mind and under stand how a prop goes thew the water.

The numbers are not the whole story to a prop but how it flies thew the water is the key.

I was told that a high pitch prop will lift the back of the boat as you let of the throttle.

I have found this to be very true with a big prop going a high speed in my hydro.

The prop will push the back of the boat where it wants not where you want it to go.

It has put me in some bad situation lately that I have bin fighting with.

In a play boat or a record trials boat this is not a problem. But in a heat racing boat it is not desirable.

Speed comes with its down falls. But still I would rather be fast and contend with it than be slower.

Time and Time again it has been proven that the fastest boat does not always win hint hint.. Consistency wins races

 

[shoboat]

Greg,

The rake is determined when the blade is casted or mounted to the hub.

The reason more cup did not help you is that it reduces the lift of the propeller but changes the way the

water exits the propeller. Try measuring the leading edge pitch about 30% up from the hub. Note this number

And write it down for reference. Now bend the leading edge out about .030" to .050" and measure and make

sure both are the same with your pitch gauge. The trick here is to keep the pitch more constant thru the blade

so the water can come off with less resistance. Think of a ski ramp.

Rodney,

Not really a black art, just good sound basic principles and great consistent measurements.

Try to keep the blades the same as much as possible. If you have less pitch on one blade than the other,

the one with less pitch is going to slow you down every revolution right? Staggered pitch is not faster.

Read as much as you can from Mercury Marine engineers they are very sharp on the subject. I learned

a lot last summer when I visited Mercury Racing in Wisconsin. To optimize our boats it is just finding the

right combination of numbers that work well with each other. Engine modification is the same way.

Keep trying new combinations,

Mark

 

[Tim_Duggan]

I've been manipulating blades lately to change the way the boat rides and by what the rooster tail is doing. Not chasing outright speed as such, but it seems the two work hand in glove.

It's interesting that two different props of the same casting can make a boat handle very differently with only a subtle change. For example I tried two different modified X442's on an O/B tunnel yesterday - both have the same L/E mods but one is Barr cut and the other is back cut. Same T/E pitch and same tip cup to reduce some lift. About the same acceleration and speed, but one understeers in the 2nd half of the turn and the other doesn't.

I wish I'd started to learn these traits years ago rather than solely making changes to the boat or settling for less that ideal handling.

 

[stan simpson iv]

On my 45 rigger I have a 1462 prop that is bad to the bone...I have a 1662 that is at least 5 mph faster...but I heat race and the 14 series is the better of the two for me as far as handling. I have bent this and that to try to get the same speed and the 14 series does not do it,i just got a 1465 to try and maybe it will work to my liking...yes the props are cut down they are not full sized blades,both series of props. My 60 boat is a lot more friendly with the prop selection cause of the weight/RPM's or size of the boat??? I do not know. She likes the 1667 prop... What prop would you suggest to try with a JAE CMB 91 RS...I have used the 1667 for a RR 90 I had before but do not know if that will be big enough to play with now. I am going for RPM"s so do not suggest some weed eater prop please...thx for your info

 

[stan simpson iv]

Stan my.45 likes the abc 2316

Thx you for the info...I think i have one,just need to try it again.

 

[julianconde]

On my 45 rigger I have a 1462 prop that is bad to the bone...I have a 1662 that is at least 5 mph faster...but I heat race and the 14 series is the better of the two for me as far as handling. I have bent this and that to try to get the same speed and the 14 series does not do it,i just got a 1465 to try and maybe it will work to my liking...yes the props are cut down they are not full sized blades,both series of props. My 60 boat is a lot more friendly with the prop selection cause of the weight/RPM's or size of the boat??? I do not know. She likes the 1667 prop... What prop would you suggest to try with a JAE CMB 91 RS...I have used the 1667 for a RR 90 I had before but do not know if that will be big enough to play with now. I am going for RPM"s so do not suggest some weed eater prop please...thx for your info

stan try a 1667,H667 pitched and cup add as much as you need. same or more pitched as the same props we use on our twins. for the 91rs hydro

 

[stan simpson iv]

On my 45 rigger I have a 1462 prop that is bad to the bone...I have a 1662 that is at least 5 mph faster...but I heat race and the 14 series is the better of the two for me as far as handling. I have bent this and that to try to get the same speed and the 14 series does not do it,i just got a 1465 to try and maybe it will work to my liking...yes the props are cut down they are not full sized blades,both series of props. My 60 boat is a lot more friendly with the prop selection cause of the weight/RPM's or size of the boat??? I do not know. She likes the 1667 prop... What prop would you suggest to try with a JAE CMB 91 RS...I have used the 1667 for a RR 90 I had before but do not know if that will be big enough to play with now. I am going for RPM"s so do not suggest some weed eater prop please...thx for your info

stan try a 1667,H667 pitched and cup add as much as you need. same or more pitched as the same props we use on our twins. for the 91rs hydro

On my 45 rigger I have a 1462 prop that is bad to the bone...I have a 1662 that is at least 5 mph faster...but I heat race and the 14 series is the better of the two for me as far as handling. I have bent this and that to try to get the same speed and the 14 series does not do it,i just got a 1465 to try and maybe it will work to my liking...yes the props are cut down they are not full sized blades,both series of props. My 60 boat is a lot more friendly with the prop selection cause of the weight/RPM's or size of the boat??? I do not know. She likes the 1667 prop... What prop would you suggest to try with a JAE CMB 91 RS...I have used the 1667 for a RR 90 I had before but do not know if that will be big enough to play with now. I am going for RPM"s so do not suggest some weed eater prop please...thx for your info

stan try a 1667,H667 pitched and cup add as much as you need. same or more pitched as the same props we use on our twins. for the 91rs hydro

thx brother...I heard about a 2716 goes pretty fast if turned up pretty good. Has anybody played with that prop. I showed up to Atl with some stuff that I had just thrown together,my dad warned me not to do that and it bit me in the s"ASS". It will not happen again...as to why I am asking some simple questions bout some props...now we have some prop guy's that want to help us...I am all ears.

 

[julianconde]

Stan also add center of blade and leading edge pitch that will help a lot as well.. 1667 is the best that we have used but theres a few others as well.. you can put 6.7-7.0 trailing edge pitch COB stock to 6.5 i have seen work really well. i use my Twin propellers and they work Just as good.. MARK SHOLUND can get you right brother..

Julian

 

[dwilfong]

There is not a good alternative for a large eng rigger at the moment.

1667 is the best all around prop. the H50 is fast but it has some bad habits for heat racing.

The 1475 has more leading edge than both but to much diameter to cut down.

There is a void if you are making good power. RPM is the only choice at the moment not more power.

I had a Andy brown CNC prop that had great promise but it did not last long.

Will the void be filled?

We can only hope.

 

[shoboat]

Stan,

The reason your 1662 run faster is the .49" of pitch difference between the two propellers,

1662 and the 1462. If you measure the leading edge pitch of both propellers you will see the

Real difference why one is faster than the other. Your leading edge pitch at 30% up the leading

Edge times your engine and pipe RPM is going to give you your speed Stan. The 1400 series

Propellers work very well but they do not have enough leading edge pitch in the stock blade.

I would suggest to add some leading edge pitch ever so slowly to your 1462 and see what it does?

The H-32 is very close to 1662 also a good propeller to try. The 1667 with the right numbers and the

right diameter work well on many 60,80,91, & 101 boats. If Octura could only make a 1670 we would

be much better equipped for the bigger HP engines of the future. Your blade area ratio is another key

in the equation also. In my testing we are doing better with a more even pitch progression thru the whole

blade. So if you reduce the cup on the trailing edge and pitch up the leading edge and center of the blade

you will have a more constant pitched propeller. This is the direction that we are currently testing on Hydros

and Monos. With good engine power and RPM we are getting very good results with this combination.

Keep Testing Fellas,

Mark Sholund

 

[shoboat]

Greg,

No formula that we can tell so far. Each boat and engine and pipe combination are so different

that the RPM difference is to great to draw any formula so far in our testing. It is number combinations

that seem to work better with each other. If you can get Peter Duggan to make some 1647, or 1670's let us know?

The propellers that we have available currently are just a start to what could be coming in the future. Think of a more

Constant Pitched Propeller Blade with less pitch progression. You will figure it out once you try more combinations.

In our motor program we are still finding better number combinations that work better together, so the propellers we are

running will have to change also(number combinations). If anyone has the access to a CNC machine capable to make

model boat propeller prototypes we would all be much faster. I think Andy had the right idea, we just need a better

material.

Greg is Ian and Aaron still making new pipe designs? Or did I hear that Aaron retired recently?

Thanks For Reading And Sharing Your Ideas,

Mark Sholund

 

[julianconde]

Stan,

The reason your 1662 run faster is the .49" of pitch difference between the two propellers,

1662 and the 1462. If you measure the leading edge pitch of both propellers you will see the

Real difference why one is faster than the other. Your leading edge pitch at 30% up the leading

Edge times your engine and pipe RPM is going to give you your speed Stan. The 1400 series

Propellers work very well but they do not have enough leading edge pitch in the stock blade.

I would suggest to add some leading edge pitch ever so slowly to your 1462 and see what it does?

The H-32 is very close to 1662 also a good propeller to try. The 1667 with the right numbers and the

right diameter work well on many 60,80,91, & 101 boats. If Octura could only make a 1670 we would

be much better equipped for the bigger HP engines of the future. Your blade area ratio is another key

in the equation also. In my testing we are doing better with a more even pitch progression thru the whole

blade. So if you reduce the cup on the trailing edge and pitch up the leading edge and center of the blade

you will have a more constant pitched propeller. This is the direction that we are currently testing on Hydros

and Monos. With good engine power and RPM we are getting very good results with this combination.

Keep Testing Fellas,

Mark Sholund

Mark your F Mono propeller Was EXTREMELY fast when i ran it in Atlanta spring nats. Thats running the less pitched up V Cut prop. i have not ran the other prop yet.

Fast,stable ,turn on the dime and great acceleration WOW.. your the Man

 

[stan simpson iv]

Thx you guy's for all input...

 

[shoboat]

Julian,

We have recently improved that propeller even more. When you get back in the states you will see

some of the upgrades.

Thanks And Be Safe Big Fella,

Mark Sholund