Propeller Blade Thicknesses.....

[ThrottleUp Props]

Hey Guys....I thought we could talk about "Propeller Blade Thicknesses". This is a characteristic of newer origin, to both racers and the private sector. But, none the less, a VERY IMPORTANT aspect when purchasing propellers, new or used.

It has become painfully clear that blade thicknesses are not being considered or thought of during the propeller purchasing process.

So, I thought I would start this thread to get some real life scenarios.

What is your HP and what is your blade thickness?

Do not worry if you do not know, check your propellers on the aft end.

You may see the manufactures name, the propeller size, serial numbers, blade thickness and manufacturing date. It will not have all of this info but it will have some of it.

So before you start the season lets make sure your propellers are what they need to be.

Safety first, as they say!

Julie

[glh]

Ok,

Mine say ;
Throttle Up 16 3/4 x 36 18
Got them from joe in Houston TX

For a 42 MTI with drysump transmissions and 850's

[ThrottleUp Props]

VERY GOOD GLH!!!!!!!!!!!!! Your propeller thickness is 850 HP rating.

Congrats!

Julie

[glh]

Does that mean no chillers and smaller pullies mommy?

[ThrottleUp Props]

I actually have a 4 week production time as of today. However several board members have thrown blades already this year with catastophic damage.

So onebadinjun....what is your contribution to the HP boating world these days?

Care to man up?

Julie

[ThrottleUp Props]

Does that mean no chillers and smaller pullies mommy?

Not to exceed 1000HP....my son!

Julie

[Dan Adams]

On the 42 fountain w/525s was running 32p 5 blade labbed mercs. They break off about an inch up from the hub. The thickess area at this point is .325". I have broken two so far with this mild setup. I'm currently running the same props, except non-labbed.

[shifter]

Julie makes a very good point.

I have had several customers try props not looking at the blade thickness and ended up failing very quickly. They can be cut for a 525 spec or a 850 spec and you are pushing 1400 hp. That is why there is a mandated thickness in racing.

The props also have a fatigue life so be carefull on used props. Watch out for the dings on the leading edges they lead to cracks.

pat W

[ThrottleUp Props]

On the 42 fountain w/525s was running 32p 5 blade labbed mercs. They break off about an inch up from the hub. The thickess area at this point is .325". I have broken two so far with this mild setup. I'm currently running the same props, except non-labbed.

Dan,

Your biggest challenge or issue is that you are surfacing high round ear props which were not designed to surface pierce. I am afraid with your exsisting drive heigth you will most likely continue to do so. You may want to consider changing your drives or props.

Julie

[ThrottleUp Props]

Julie makes a very good point.

I have had several customers try props not looking at the blade thickness and ended up failing very quickly. They can be cut for a 525 spec or a 850 spec and you are pushing 1400 hp. That is why there is a mandated thickness in racing.

The props also have a fatigue life so be carefull on used props. Watch out for the dings on the leading edges they lead to cracks.

pat W

ABSOLUTELY ON THE MONEY PAT!!!!!!!!

Thank you for sharing expertise with everyone!

Blade thickness was not an issue when HP was at 500, but in the last 10 years it has increased substantially and so has blade failure rates.

Julie

[cigdaze]

If you can't say anything nice, then......:rolleyes:

Check your propeller blade thickness at the start of the season...COME ON!!!??? I know things are slow, but this takes the cake. I've heard just about everything now.:rofl:
I'm not quite sure what it is about this that you find funny.

I've tossed a blade before and I can tell you it's no fun at all. I got lucky that the only thing damaged was the prop, but it can get pretty ugly if a blade launches into something else on your transom.

People buy and trade labbed props all the time on this forum and if a prop was worked for an intended power (thrust) range, and you unknowingly exceed it, the results will speak for themselves. And it's not just thickness you should be checking, as mentioned above, small nicks, scratches and dents/dings can work themselves into catastrophic cracks given enough time with the oscillating loads involved here; fatigue can and will come quickly with props.

[Dueclaws]

I have Merc CNC 5 blades: 16.5 x 36, 18*, 1075 HP blade. My engines are about 950 HP, so (probably) the thicker blades are unnecessary.
If they had been available, would've bought those 850 HP TU props from Joe.
My test-time-only Mercs are for sale BTW.
;-)
Due

[Sean H]

just need a set of these... :sifone:

[sellsman11]

just need a set of these... :sifone:


:cool: :cool: :cool:

[ThrottleUp Props]

I have Merc CNC 5 blades: 16.5 x 36, 18*, 1075 HP blade. My engines are about 950 HP, so (probably) the thicker blades are unnecessary.
If they had been available, would've bought those 850 HP TU props from Joe.
My test-time-only Mercs are for sale BTW.
;-)
Due

You are absolutely correct. I would not have built the wheels for 1075 either. With 950's you would be fine with the 850 thickness. Let me know if I can help you with a set.

Julie

[ThrottleUp Props]

just need a set of these... :sifone:

Now that it is out there guys....this is the newest propeller process we have available to all of you!

The props in the pictures posted b Sean H are Throttle Up Propellers CNC Suface props with a PVD applied. PVD is "Particulate Vapor Deposition". This formulation is designed to increase the strength of the propellers.

Stay tuned as more information becomes available on the features and benefits!

Julie

[Dueclaws]

Julie-
OK. Let me sell the Mercs and will contact you afterwards.
Thanks
John

[Davidmnc]

just need a set of these... :sifone:

If there is such a thing as a sexy prop...........these are them! :drool5:

[Dock Holiday]

Good thread Julie

I know first hand what it feels like to have a blade decide it wants to leave the family. That is one wicked vibration!

I never have heard this before about a minimum blade thickness and labbing for the horsepower and find it very interesting. The prop pictured was the fastest set of props I ever owned after working them twice and they did not last one full season. I guess I know why now. Yes they were THIN baby!

P.S. No these were not your props Julie they came from our buddy out of Houston that hosed so many people.

[ThrottleUp Props]

Yes thin can be fast......but everything has its breaking point. When it comes to Stern Dirve props there are some other forces at work as well. Drive heigths have become so very high that the round ear props are really suffering. But our friend at Houston liked to make props very thin....it was his way of insuring you would have to come back. And I mean sooner rather than later!

Julie

[ThrottleUp Props]

Buy the way is that your "Barn Shop"? Cute! I am glad you found somewere to put the propeller!

Julie

[Dock Holiday]

Buy the way is that your "Barn Shop"? Cute! I am glad you found somewere to put the propeller!

Julie

AKA "The Cave"

It used to be a horse barn and we don't have horses any longer. I'm almost finished with it and I could not bring myself to throw the old prop away!

Thanks

[ThrottleUp Props]

If there is such a thing as a sexy prop...........these are them! :drool5:

Thank you Dasvidmnc!

We spent a good amount of money on R & D trying to figure this one out for you guys. This new treatment will provide additional strength to propellers. It will also allow us to go thinnner, for certain applications to gain top end WITHOUT sacrificing strength and durability!

I happen to think that they are pretty sexy too!

Julie

[ThrottleUp Props]

AKA "The Cave"

It used to be a horse barn and we don't have horses any longer. I'm almost finished with it and I could not bring myself to throw the old prop away!

Thanks
Its a "Man Cave"!!!!!!!!! I know how much you guys like them!!!!!

Julie

[Joe]

Does that mean no chillers and smaller pullies mommy?

hmmm... considering i'm running 1075's??????? i'd bet you are A-OK!

FYI - I ran those props on two events..... my friend, richard, whom has a 368 w/ 1400's ran the exact run, nearly side-by-side, and when we got back on the trailer, his 1200 hp propellers (not Throttle-up's) were all nicked up.

the "old style" Throttle-Up props, which is what we are all currently running have had the porousness (sp?) of the metal significantly reduced compared to most of the other props out there.... so, if you're talking thickness-to-thickness, Throttle-up 850hp props are/should be stronger/tougher and more able to withstand "the elements", including debris, heavier boats & larger hp engines vs. the identical propeller of another brand.

re: "old style" ---- the "new style" props are even thinner, with the "golden" coating, which makes them as tough, or stronger/tougher, than the "old style", thicker props (which, remember, are already stronger/tougher than most of the other's).

so, Throttle-Up has just 1-up'd itself.


PS: Also, they have, for the last two years, held the title, "World's Fastest Propeller"..... It will be interesting to see what happens this year with this new "golden" #6, outboard and stern drive prop.

Way to go, Matt, Julie and the entire Throttle-Up Team!!!!!!!!

------- now quit being so humble and let all those guys who keep throwing blades realize A) how dangerous it is (ala Gary Smith & Aqua Mania) and B) how much of a hassle and expense it is to be carrying around duplicate sets of props --- in case you throw a blade? :willy_nilly:

joe

ps: unfortunatly, however, i can attest that if you back into a wooden piling, they will bend! (and no, GL, before you ask, I did it w/ the set that is currently on my boat, not the set you have.). :banghead:

[Joe]

Check your propeller blade thickness at the start of the season...COME ON!!!??? I know things are slow, but this takes the cake. I've heard just about everything now.:rofl:

Since you didn't include what boat you have in your avatar, i presume, either way, this thread is not directed toward you or your canoe --------- haha.... only kidding (remember, you dished it firrrrrrst!).

Seriously, When you step-up and buy/have a boat with an excessive amount of hp, you can not imagine how much expense the vibration alone from a bent or nicked propeller can cause - drive shaft vibration alone can quickly ruin a drive, drive shaft and motor.

Joe

ps: OneBadInjun --- If we weren't so polite around here I'd tell you how much of an idiot you just made of yourself --- but, then again, you could always argue, "Ignorance is Bliss"..... and I'd at least stand behind the first part, goofball!:ack2::seeya:

[Joe]

Come on Julie...Please stop. I'm pee'n in my pants...:rofl:

Why don't you just take a deep breath, hold it, and count to 10,000 slowly! Then, go somewhere else...... Here, I have a suggestion...

Try this: www.offshoreonly.com


:26::kiss:

[Joe]

just need a set of these... :sifone:

Sean, let me finish your comment with, "...and then you're Golden!" :cheers2:


Joe

[Joe]

:cool: :cool: :cool:

...and yes, I'm sure you and Woodsy can have a pair also!!!!!!!!!!

Tell Kerry I bet they'll even make a special set of Golden teeth caps for him... which he could put in on Friday & Saturday nights while he's trying to sell "someone" on coming over to see his "baseball card collection"!
:biggrinjester:LOL.......

Joe

[MattBMiller]

I guess mine wasn't thick enough...

[glh]

I guess mine wasn't thick enough...shiat!

[Geronimo36]

Great info here.... When I bought my BMax drives several years ago they noted labbed props would void all warranties.

How about old labbed props? I understand over time they kinda wear out and loose trueness. Can they be rehabbed?

After all these years I finally got my X Dimension where it should be and I might need a set of labbed 28's but first I gotta do some WOT runs... Cruise picked up 3 mph so far and I'm really happy with the results of the project so far! Even if I don't pick up on the top end, which I expect I should, I don't even care cause I picked up the cruise so much and the boat handles even better than it did previously!

[MattBMiller]

Julie - I broke another Bravo prop this weekend, same place as the one pictured above, only this one wasn't labbed. Thankfully I notived the crack in the blade at the gas station before I dropped in the water. Any ideas on that one??

[ThrottleUp Props]

Great info here.... When I bought my BMax drives several years ago they noted labbed props would void all warranties.

How about old labbed props? I understand over time they kinda wear out and loose trueness. Can they be rehabbed?

After all these years I finally got my X Dimension where it should be and I might need a set of labbed 28's but first I gotta do some WOT runs... Cruise picked up 3 mph so far and I'm really happy with the results of the project so far! Even if I don't pick up on the top end, which I expect I should, I don't even care cause I picked up the cruise so much and the boat handles even better than it did previously!

So are you saying that BMax voids the drive warranty if you run labbed props? Or are you saying the labbed props have no warranty?

Lab Finished props are thinner and therefore have a shorter life span. They also become a higher maintainence piece of equipment, on your boat. Higher maintainence also implies higher dollar. Labbed props can certainly be reconditioned and should be maintained.

Appropriate drive heigth can be a night and day difference on any boat. But blade confirguration is key in combination with this as well.

Let us know how your testing goes!

Julie

[ThrottleUp Props]

Julie - I broke another Bravo prop this weekend, same place as the one pictured above, only this one wasn't labbed. Thankfully I notived the crack in the blade at the gas station before I dropped in the water. Any ideas on that one??

Sorry to hear you have had another prop issue, Matt. If it is a smaller sized crack, than a repair may be in order. But, you need to look into the root cause of the blade failure. Here is a very important thing to consider.

High Rake, Round Ear props were not designed to surface pierce. So for those of you installing shorties keep in mind that this may lead to or be directly causing your blade failures. Your asking a propeller to due something it was designed to do.

I mention this as you have now cracked labbed and stock props.

Julie

[Geronimo36]

So are you saying that BMax voids the drive warranty if you run labbed props?

Yes, they void the warranty. Apparently they had several lower bearing and propshaft failures due to customers throwing blades so they don't honor the warranty if you run labbed props.

I was given the info when I bought the drives so I stuck to it. But, I'm 1.5/2yrs out of warranty now! :sifone:

[Big Time]

Labbed props can certainly be reconditioned and should be maintained.


I don't have a labbed prop, but I was thinking about it. My question is how do you maintain a labbed prop?

[ThrottleUp Props]

A labbed propeller needs to be visually inspected before and after every run. If you have nicks on the leading edges (LE) or on the trailing edges (TE), you need to address them immediately. A nick in either the LE or the TE is the equivlent to a stress risers. These are small anomylies on the metals surface, which create a "week spot" on the metals surface.

If you think of it this way.....when you pick up a rock on your windsheild, a lot of times it is a very small chip and if it is not addressed it progressively gets larger. The next thing you know it zips right across your windshield. This is similar to what a blade will experience if nicks are not addressed.

So, moral to the story.... you can never check your props to frequently!

Julie

[T2x]

I don't have a labbed prop, but I was thinking about it. My question is how do you maintain a labbed prop?

I'm just a casual observer here but let me jump in for a second. A labbed prop can certainly be refurbished if you have minor nicks and dents, generally with the loss of some metal and subsequently a bit of blade area. A proper propeller shop will even all of this out in the refurbishing process (lotta "pro's" in this sentence). An improper propeller shop will only work on the affected blade(s) and leave you with a bit of a balance problem.

However........ There is a condition called "swept blades" that cannot be properly repaired....at least for very long. "Swept Blades" occurs most often on cleaver props and is manifested by a loss of straightness on the trailing edge towards the tips. Basically the end of the prop blades sweep backward from the long term force against them in a rearward bend. The untrained eye will see a nice curve and think everything is fine, but, in fact, the blade(s) has (have) lost its (their) bite and peak performance. Some prop shops will attempt to heat and bend them back, but obviously if they bent once, when they were newer and stronger, subsequent use will simply restart the problem...in a hurry. The end result of this phenomenon is usually the loss of a blade or blades' tip(s).

And now back to Julie and her more than informative and valid thread.

T2x

[ThrottleUp Props]

Great points Rich! This is something we see with Cleavers.....I guess it is becasue they can have a longer span (more metal on the trailing edge). It is of great importance to consider the weight and the HP of the boat when determining the blade thickness or the recommendations we make. Some adjustments are permanent and some are only temporary as Rich has described! Another great example would be pitch changes, which are not always permanent.

Julie

[BRAD SCHOENWALD]

Interesting Stuff. This is/has all been in lesson plan four of our performance boat school. We have found numerous props with cracked blades on the pre checks of the students boats as well as boats with the wrong prop.

Keep up the great work!

[MattBMiller]

Sorry to hear you have had another prop issue, Matt. If it is a smaller sized crack, than a repair may be in order. But, you need to look into the root cause of the blade failure. Here is a very important thing to consider.

High Rake, Round Ear props were not designed to surface pierce. So for those of you installing shorties keep in mind that this may lead to or be directly causing your blade failures. Your asking a propeller to due something it was designed to do.

I mention this as you have now cracked labbed and stock props.

Julie

I tried a Hydromotive on my boat last year, but it just blew out at 2200 RPM's. Any suggestions on other props to try?

Thanks!

[ThrottleUp Props]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

[T2x]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

I bet you say that to all the boys...................

;) :D

T2x

[MattBMiller]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

These are the only pics I have. Don't have a pic with the drive down. Propshaft CL is 2.5" below the bottom at neutral trim.

[ThrottleUp Props]

Eureka....good job Matt! You have just uncovered your problem with blade failures. So the good news is your boat is set up aggressively. The bad news is this is exactly what is causing your blade failures. You are surfacing a round ear, high rake propeller that was never designed to surface pierce. We have not even touched on the performance issues you are having. This is what semi-cleavers and full cleavers are for. So you have three options:

1) Switch to semi-cleavers
2) Space the drive down
3) So nothing and invest in props. You will need one on the boat, one in the mail and one on order. In other words tossing blades will be common place.

Sorry I don't have better news but at least you know the root cause of your blade failures.

Julie

[PARADOX]

Just love a Blond talking technical stuff. :)

Long ago, and far away, back and on Lake "X" we were drilling pin holes on the surfacing props, try to eliminate the T2X rounding/bending problems. The scheme actually worked a bit, allowing some stress and "gases" to escape releaving preasures at the tip.
I haven't seen any holes in the props for decades, but again, this was before the labbing era. Labbing back than meant putting a grinder or a drimmal to the edge and make them sharp as a rasor. :)

[Geronimo36]

Can you post a pick of your transom (on trailer), so I can get an idea of your prop shaft heigth, please.

Julie

Julie, here's mine with the new setup. Sorry for the pic quality, I had the morning sun to deal with. It's hard to imagine they were 2" lower! I'm now measuring 5 1/4" propshaft depth at neutral position.

Your thoughts?

Thanks in Advance.

[Ratickle]

I tried a Hydromotive on my boat last year, but it just blew out at 2200 RPM's. Any suggestions on other props to try?

Thanks!

A four blade? That surprises me....


Should have finished reading before commenting.....


2.5 inches is high........

[ThrottleUp Props]

I bet you say that to all the boys...................

;) :D

T2x

I cannot tell a lie.......I do!:biggrinjester:

Julie

[ThrottleUp Props]

Julie, here's mine with the new setup. Sorry for the pic quality, I had the morning sun to deal with. It's hard to imagine they were 2" lower! I'm now measuring 5 1/4" propshaft depth at neutral position.

Your thoughts?

Thanks in Advance.

At 5.25" below the hull your optimum propeller will be a 4B Propeller. It might be a tad to deep for a 5B propeller. However if you have modified motors the addition of a blade can assist at carrying the weight. Why don't you post your performance numbers and we can take a look at efficency.

Julie

[Geronimo36]

Will do Julie, thanks.

I may go testing this weekend...hopefully I don't blow it up.. lol

[Tomas Wallin]

GREAT THREAD JULIE!

What about my application?

I know I have asked you before but it won't hurt...

At what prop shaft height should you consider semi cleaver and cleaver props?

My prop shaft is at 3.15" below the bottom with a 10" notch and I would like to stick with 4bl props.

I'm going to try a std Bravo 28 and a std 30 next, with 825HP I had only 11% slip with a std Bravo 28 at 89mph - now I have some more boost and 870HP.

The two labbed ones I've got only gets me a lot of slip and no speed. The labbed Bravo 31 I tried last got me to 88.5mph with 24% slip and probably way to little bow lift since it chine walked like crazy. I will get some pics next time to see what it looks like at wot.

The props markings are Wood190 (29P) and FO1D127 (not completely sure about the "1" though. 15 1/4 X 31 R - blade thickness 0.135")

Will a Hydromotive do me any good theoretically? I assume the QIV-X would be my best bet with it's bow lift?

[KnotRight]

Hey Julie am I doing this right??

[KnotRight]

Oh yeah 1580 hp herrings 16.75 x 37.5,s
3.5 inch drive height. 46 Skater Turbines

[Geronimo36]

At 5.25" below the hull your optimum propeller will be a 4B Propeller. It might be a tad to deep for a 5B propeller. However if you have modified motors the addition of a blade can assist at carrying the weight. Why don't you post your performance numbers and we can take a look at efficency.

Julie

Julie, the verdict is in. The boat picked up 3 mph through out the entire RPM range. However, I'm still a little under propped spinning 5250-5300, I'd like to see 5400-5600 but I don't want to loose cruise speed by labbing..

Boat ran 87 mph!!!

Your thoughts?

[Padraig]

What about Cryogenic hardening a thinner blade. Weren't some racers doing that a few years back. Are there advandages or was it dropped because the benifit was not there?

[PARADOX]

Q: to July

Off the thickness issue we are going. :) but.

"X" dim? Deep "V" no step. 24 Deg. deadrise. The camera was pretty even and in line with the bottom of the hull.
Prop shaft center 5". Props are labbed with added cup for bow lift. Still looking for some hard to find additional speed. With the 28's and 32's pretty much same top end. (525's bravo XR, SM shorties)

Any thoughts?
31624

31625

[ThrottleUp Props]

GREAT THREAD JULIE!

What about my application?

I know I have asked you before but it won't hurt...

At what prop shaft height should you consider semi cleaver and cleaver props?

My prop shaft is at 3.15" below the bottom with a 10" notch and I would lika to stick to 4bl props.

I'm going to try a std Bravo 28 and a std 30 next, with 825HP I had only 11% slip with a std Bravo 28 at 89mph - now I have some more boost and 870HP.

The two labbed ones I've got only gets me a lot of slip and no speed. The labbed Bravo 31 I tried last got me to 88.5mph with 24% slip and probably way to little bow lift since it chine walked like crazy. I will get some pics next time to see what it looks like at wot.

The props markings are Wood190 (29P) and FO1D127 (not completely sure about the "1" though. 15 1/4 X 31 R - blade thickness 0.135")

Will a Hydromotive do me any good theoretically? I assume the QIV-X would be my best bet with it's bow lift?

Well with your prop shafts 3.15 below the hull you are marginal for being able to run them successfully with 4B props. I would try a Hydromotive P5-X I bet this propeller will perform pretty well for you. Labbed props are definately out with your new set-up. To much slip!~

Julie

[ThrottleUp Props]

Hey Julie am I doing this right??

WOW.... nice KnotRight!

I am going to post a diagram for you all today. This will give all of you with Micromoeters something to measure by.


Julie

[Ratickle]

Well with your prop shafts 3.15 below the hull you are marginal for being able to run them successfully with 4B props. I would try a Hydromotive P5-X I bet this propeller will perform pretty well for you. Labbed props are definately out with your new set-up. To much slip!~

Julie

All right, now you really lost me.......


A labbed prop made specially for the boat is not the best?

[ThrottleUp Props]

Julie, the verdict is in. The boat picked up 3 mph through out the entire RPM range. However, I'm still a little under propped spinning 5250-5300, I'd like to see 5400-5600 but I don't want to loose cruise speed by labbing..

Boat ran 87 mph!!!

Your thoughts?

At what RPM is your peak HP produced? If you ran 5200 and your looking for 5600 (your range is too wide) Then you may not even be in the power band of the motor. If this is the case your currently getting a false sense of cruise speed and possibly lugging the motor.

Julie

[ThrottleUp Props]

What about Cryogenic hardening a thinner blade. Weren't some racers doing that a few years back. Are there advandages or was it dropped because the benifit was not there?

I have spoken with a few companies about this as well. It has been around a long time. Some say it works while other say it makes the propeller too brittle. It works well on fixed parts that experience little to no flex.

Julie

[ThrottleUp Props]

Q: to July

Off the thickness issue we are going. :) but.

"X" dim? Deep "V" no step. 24 Deg. deadrise. The camera was pretty even and in line with the bottom of the hull.
Prop shaft center 5". Props are labbed with added cup for bow lift. Still lookng for some hard to find additinal speed. With the 28's and 32's pretty much same top end. (525's bravo XR, SM shorties)

Any thoughts?
31624

31625

If you can post ALL of your data I can take a look. To be able to run 28P props and 32P props in the power band would surprise me.

Julie

[ThrottleUp Props]

All right, now you really lost me.......


A labbed prop made specially for the boat is not the best?

During the process of labbing a good amount of the cup is cut out. This is part of the reason why your RPM increases with a labbed propeller. However some boats just do not respond well to this modification and need the cup put back in. By doing so the RPM will come back down. Now one may not be achieving their RPM goals. So it is not always the answer.

Julie

[BradH]

Just love a Blond talking technical stuff. :)

Long ago, and far away, back and on Lake "X" we were drilling pin holes on the surfacing props, try to eliminate the T2X rounding/bending problems. The scheme actually worked a bit, allowing some stress and "gases" to escape releaving preasures at the tip.
I haven't seen any holes in the props for decades, but again, this was before the labbing era. Labbing back than meant putting a grinder or a drimmal to the edge and make them sharp as a rasor. :)

I've heard of a few fairly recent commercial propellers that a few holes have helped. Most of the time the propeller is overloaded and begins to cavitate on the back of the blade. Drill some holes and allow the bubble to fill, rather than collapse on the blade. Same thing that you experienced, just on a different scale. Simple solution for a complex problem.

Out of curiosity, when was this? Michigan wheel made some major changes to blade design in the mid 80s to combat this problem and I'm wondering how many manufacturers adopted these.

[ThrottleUp Props]

Lab Finishing propellers is typically more successful on progressive or aggressive hulls. Conventional Deep Vee hulls with no steps or notches, so not respond as well to labbed props.

Julie

[PARADOX]

I've heard of a few fairly recent commercial propellers that a few holes have helped. Most of the time the propeller is overloaded and begins to cavitate on the back of the blade. Drill some holes and allow the bubble to fill, rather than collapse on the blade. Same thing that you experienced, just on a different scale. Simple solution for a complex problem.

Out of curiosity, when was this? Michigan wheel made some major changes to blade design in the mid 80s to combat this problem and I'm wondering how many manufacturers adopted these.

Brad.

It was during the early and mid 80's. We were racing a Donzi hull with a single Bulldog, and a OMC cobra drive. The hull/keel was rounded. That boat wanted to go everywhere but straight. We put 2X4's under the engine blocks to raise the "X" dim. and ran Merc. "cleavers" and drilling holes in the tip, try to dial in the goofy set up. Good times tho... :26:

Julie.. Thanks.. I will try to get some specs and running RPM's / speeds.

[Ratickle]

That boat wanted to go everywhere but straight.

:sifone: :rofl: :sifone:

[Tomas Wallin]

Well with your prop shafts 3.15 below the hull you are marginal for being able to run them successfully with 4B props. I would try a Hydromotive P5-X I bet this propeller will perform pretty well for you. Labbed props are definately out with your new set-up. To much slip!~

Julie


During the process of labbing a good amount of the cup is cut out. This is part of the reason why your RPM increases with a labbed propeller. However some boats just do not respond well to this modification and need the cup put back in. By doing so the RPM will come back down. Now one may not be achieving their RPM goals. So it is not always the answer.

Julie
Yes I can definately see that the props have very little cup.

What if I put the cup back in. Shouldn't a labbed, thinned and sharpened prop with a cup perform better than a std prop?

[Geronimo36]

At what RPM is your peak HP produced? If you ran 5200 and your looking for 5600 (your range is too wide) Then you may not even be in the power band of the motor. If this is the case your currently getting a false sense of cruise speed and possibly lugging the motor.

Julie

I'm looking for 54-5600. I have 5250-5300, not 5200. Pk torque was at 4500, pk hp is 5800 and made about 10-15hp less @ 6k. It's within a few hp of peak from 54-5800 and valvetrain is set up for 5600.

I've run smaller props to get to 5700 rpms and the boat is/was slower. It seems to like bigger wheels.

Thanks for the input.

[Geronimo36]

Lab Finishing propellers is typically more successful on progressive or aggressive hulls. Conventional Deep Vee hulls with no steps or notches, so not respond as well to labbed props.

Julie

Good talking to you today Julie. For now i'm going to leave it stock and just enjoy myself.

I'll be sure to refer Brett over to you.

Frank

[ThrottleUp Props]

Thanks Geronimo36. I enjoyed our conversation as well!

As I said I will help you freind in any way that I can and try to make it fun along the way!

Julie

[ThrottleUp Props]

Yes I can definately see that the props have very little cup.

What if I put the cup back in. Shouldn't a labbed, thinned and sharpened prop with a cup perform better than a std prop?

Yes it certainly can! I would recommend adjusting the cup for starters.

Julie

[KnotRight]

Julie what thickness is sufficiant for 1500hp plus?
pleasure use.


You may not agree here but on occasion I inspect my blades and take small nicks out with a sharpening stone.

[ThrottleUp Props]

Julie what thickness is sufficiant for 1500hp plus?
pleasure use.


You may not agree here but on occasion I inspect my blades and take small nicks out with a sharpening stone.

What hull are the 1500 + HP motors in?

Also taking care of nicks on the leading and trailing edges, at the ramp, is really an good thing to do. At least your cognizant of the trailing edges and the leading edges overall condition, prior to running them. But, I must clarify that there is a BIG difference between a nick on the leading edge or trailing edge and shark bite or a missing chuck on either of the edges.

I would only recommend lightly cleaning up the edges, do NOT try to be a propeller repair technician at the ramp!!!!!

Julie

[KnotRight]

46 Skater


I just try to stay on them when I notice a nick.
You really cant take to much off with a stone I,m worried about balancing.

I would never run a damaged prop.


They are hair under a 1/2 inch in thickness?

[ThrottleUp Props]

I will get you some info to check the thickness. Give me a bit and I will pm you.

Julie

[KnotRight]

I will get you some info to check the thickness. Give me a bit and I will pm you.

Julie

Tank you!!!!

I will be a good boy!

[OneBadInjun]

I will get you some info to check the thickness. Give me a bit and I will pm you.

Julie

Did you get this info yet? Thanks

[imco offshore]

alls i know i let mat and julie do what ever they want, i tell her what i need and what my boat is doing, they do their thing , and i WIN AND WIN AND WIN , thats good enough for me, the biggest and most offten question i get asked is ,,,what did u do this year to get the speed, THROTTLE-UP,,, if your not running one ,,,your following one ,,, thanks julie and matt,, george jr.