Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Results 1 to 22 of 22
  1. #1
    Petty Officer 2nd Class
    Join Date
    Apr 2009
    Posts
    118

    Default Sharpening edges of prop blades?

    This might seem like a stupid question, but what harm or good might come from sharpening the leading edges of the blades?

    thanks
    Verne

  2. #2
    Rear Admiral
    Join Date
    Apr 2009
    Location
    Greenville,S.C.
    Posts
    4,920

    Default Re: Sharpening edges of prop blades?

    I've seen racing boats with sharpened prop leading edges but for most normal boating I doubt there would be much to gain...I run a Stainless Steel Ballistic prop on my Yamaha 90HP and the edges are pretty darn sharp enough as they are....at least for my usage...

  3. #3
    Senior Chief Petty Officer emilsr's Avatar
    Join Date
    Dec 2010
    Location
    El Paso, TX
    Posts
    773

    Default Re: Sharpening edges of prop blades?

    If its just you at home with a file,its more important that you keep the leading and trailing edges clean and smooth, taking out nicks when you get them.

    There is a thinning/reshaping process called labbing. When done properly it can really wake up the performance of a boat. Expensive at around $100/blade, hard on toes if you're swimming and thinning weakens the blades so service life drops.

  4. #4
    Supreme Mariner Frank Acampora's Avatar
    Join Date
    Jan 2007
    Location
    Southeastern Pa.
    Posts
    10,293

    Default Re: Sharpening edges of prop blades?

    Try cutting meat with a dull knife and then with a sharp one. The principle is the same. Sure, sharpening will ease the blade entry through the water but: A sharpened edge is not the whole story, blade thickness and design count too .A knife can be as sharp as possible but if it is not hollow ground, it will not slice through meat easily. And, that is why there are different blade designs for different cutting jobs. Similarly, there are different prop blade designs for different expected uses.

    But back to your question: If done judiciously, no harm can be done by sharpening the leading edges of your prop blades. However, any performance gain from just that will be so slight that you will probably not notice it.

  5. #5
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,373

    Default Re: Sharpening edges of prop blades?



    10.00 sharp as you want to get it..Be careful
    Stickly a opinion your milage may vary.

    Speed is how fast you hit the wall
    Torque is how far you move the wall"

  6. #6
    Petty Officer 2nd Class 1FASTLASER's Avatar
    Join Date
    Dec 2006
    Location
    Southeast Arkansas
    Posts
    158

    Default Re: Sharpening edges of prop blades?

    First off W_Guy there is nothing as a stupid question....the only question that is stupid is the one not asked.

    If you are looking for performance gains by sharpening the answer is simply this....NO....you wont notice anything unless you have a fast ultra light boat setup for racing and then it is better off to let the prop experts get there hands on it. BUT it is a good practice to keep the leading edges of your prop true and in good shape. This will help to keep the prop performing as it should and also help to eliminate any further problems but keep in mind that any file work done should be VERY minimal for fear of getting one out of balance which aint good.

  7. #7
    Vice Admiral tpenfield's Avatar
    Join Date
    Jul 2011
    Location
    Cape Cod, MA
    Posts
    5,901

    Default Re: Sharpening edges of prop blades?

    I'm thinking that a sharp leading edge on the propeller will hamper the performance and give you greater tendency for cavitation under load conditions. Probably something that is advantageous only for surface drives.

    A slightly rounded leading edge might be the best. Take a look at airplane wings & propellers, hydrofoils, etc. - rounded leading edge, thin trailing edge.
    Best regards,
    Formula 330 Sun Sport
    Twin Mercruiser 7.4 LX MPI (0F802036, 0F802039), Bravo 3's (0F806198, 0F806199)
    1969 Mercury 7.5 HP Outboard (26346XX)
    .
    My Formula 330SS Web Site: -> Link
    My Formula 242SS Web Site: -> Link
    My Catalina 22 Web Site: -> Link

    Member of the Month - February 2013 http://www.iboats.com/blog/tpenfield...-of-the-month/

  8. #8
    Fleet Admiral Texasmark's Avatar
    Join Date
    Dec 2005
    Location
    N. Texas, USA
    Posts
    9,398

    Default Re: Sharpening edges of prop blades?

    Quote Originally Posted by robert graham View Post
    I've seen racing boats with sharpened prop leading edges but for most normal boating I doubt there would be much to gain...I run a Stainless Steel Ballistic prop on my Yamaha 90HP and the edges are pretty darn sharp enough as they are....at least for my usage...
    I'm running the Ballistic 13 1/4 x 24 XP SS on my 90 Merc.. A real performer. For you folks out there, blade thickness is important and SS prop ads. stress the point. As Frank A. said, slice the water with a baseball bat and a machette and see which one takes the most force. I realize that sharpening your blades isn't like a SS blade, but it doesn't hurt. Nicks don't really hurt either other than cutting yourself with them when around your engine for whatever reason. I used to sharpen mine when I ran alum. props.

    Mark
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

  9. #9
    Lieutenant Commander tazrig's Avatar
    Join Date
    Dec 2012
    Location
    Cape Cod, MA
    Posts
    1,715

    Default Re: Sharpening edges of prop blades?

    Quote Originally Posted by 1FASTLASER View Post
    First off W_Guy there is nothing as a stupid question....the only question that is stupid is the one not asked.

    If you are looking for performance gains by sharpening the answer is simply this....NO....you wont notice anything unless you have a fast ultra light boat setup for racing and then it is better off to let the prop experts get there hands on it. BUT it is a good practice to keep the leading edges of your prop true and in good shape. This will help to keep the prop performing as it should and also help to eliminate any further problems but keep in mind that any file work done should be VERY minimal for fear of getting one out of balance which aint good.
    ^^^^+1

  10. #10
    Senior Chief Petty Officer emilsr's Avatar
    Join Date
    Dec 2010
    Location
    El Paso, TX
    Posts
    773

    Default Re: Sharpening edges of prop blades?

    Just to clarify a couple of things....

    Labbing isn't just for racing, nor do you need to be running the prop near the surface. Most boats will see a benefit if its done properly (of course some more than others).

    Nicks are where cracks tend to start. Its always a good idea to keep them cleaned up, but as has been pointed out, remove as little material as possible.

  11. #11
    Supreme Mariner Frank Acampora's Avatar
    Join Date
    Jan 2007
    Location
    Southeastern Pa.
    Posts
    10,293

    Default Re: Sharpening edges of prop blades?

    104_7081.jpg104_7080.jpg

    Here is an example of a cleaver prop with sharp leading edges and somewhere around 15 hours running time. Even though it is stainless, note the relative blunting of the leading edge due to normal running, not damage from running through sand or mud. Note also the pattern of paint wear from ventilation/cavitation before the prop "Locks-up."

    Note the damage at the tip of one blade that was incurred in shipping. UPS treated the shipping box like a football. The sharp blade punctured through the factory original shipping carton, an outer corrugated carton, AND a layer of packing in between both. You can NOT take a prop with thinned blades and sharp leading edges like this one and bang it against anything. Hit anything while running and the prop would probably be beyond repair.

  12. #12
    Lieutenant Commander tazrig's Avatar
    Join Date
    Dec 2012
    Location
    Cape Cod, MA
    Posts
    1,715

    Default Re: Sharpening edges of prop blades?

    I recently had a pair of stainless props reconditioned to remove some relatively minor nicks and dents along the leading edges. It was approximately $400 for both but the props came back like new. When the pros do it they weld a little material here, grind down a burr there, and make sure the prop is perfectly balanced and re-shaped to original specification. I guess the point I'm trying to make is that there is a lot that goes into fixing a prop correctly not just simply filing it down. Be careful, it's not as simple as it looks.

  13. #13
    Fleet Admiral Texasmark's Avatar
    Join Date
    Dec 2005
    Location
    N. Texas, USA
    Posts
    9,398

    Default Re: Sharpening edges of prop blades?

    Quote Originally Posted by Frank Acampora View Post
    104_7081.jpg104_7080.jpg

    Here is an example of a cleaver prop with sharp leading edges and somewhere around 15 hours running time. Even though it is stainless, note the relative blunting of the leading edge due to normal running, not damage from running through sand or mud. Note also the pattern of paint wear from ventilation/cavitation before the prop "Locks-up."

    Note the damage at the tip of one blade that was incurred in shipping. UPS treated the shipping box like a football. The sharp blade punctured through the factory original shipping carton, an outer corrugated carton, AND a layer of packing in between both. You can NOT take a prop with thinned blades and sharp leading edges like this one and bang it against anything. Hit anything while running and the prop would probably be beyond repair.
    Frank, we usually get along pretty well, but I am going to offer a different view. Back when OMC decided to come out with their first SS prop; the SST (Stainless Steel Teflon) of which I purchased one and used for many years, they used Teflon for the coating, not paint. Having run alum rebuilt props for a lot of years, I had the paint peel in a similar fashion.

    My opinion is that you can't paint something as slick as SS put it under pressure like happens to a prop and expect it to stay. That's the way I see it.

    I have been running SS props since 1973 (when this prop first came out) and never painted them, nor ever had any deterioriation to the extent you mention.

    So sir, my take on what is happening to your prop is not due to thin blades PER SE. I'll go and find a picture of my Ballistic prop which is on my boat and has been since 2005 which I used to run regularly right at 50 mph (see Avatar) with no burning or blade tip damage and add it either to this answer, or if I can't will quote this thread.

    Mark
    Attached Images Attached Images
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

  14. #14
    Fleet Admiral Texasmark's Avatar
    Join Date
    Dec 2005
    Location
    N. Texas, USA
    Posts
    9,398

    Default Re: Sharpening edges of prop blades?

    Added pics. Can't find the closeup I wanted. May have to go out to the shop and take another.
    Attached Images Attached Images
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

  15. #15
    Supreme Mariner Frank Acampora's Avatar
    Join Date
    Jan 2007
    Location
    Southeastern Pa.
    Posts
    10,293

    Default Re: Sharpening edges of prop blades?

    102_6374.jpg102_6373.jpg102_6372.jpg104_7083.jpg104_7082.jpg

    Well, Mark: I don't know if Chrysler ever had Michigan teflon coat their props but it does stand to reason that they might. When I had this prop repaired, the fellow who did the repairs remarked that where he removed the coating, the stainless underneath was not polished but rather it appeared to be sandblasted. Additionally, the parts of the blades where the coating has worn or peeled or otherwise failed to adhere, the surface looks the same. Logically, if I were going to apply a coating such as teflon or even a powder coat, I would ensure a good surface with a lot of "grab." This particular coating is glossy like powder coat but I don't think they had powder coating technology in the early 1980s (The approximate year of this prop).

    These two photos hopefully show the glossiness of the coating. One also shows where an aluminum tag with "Chrysler" silkscreened in red was applied. This tag blew off the first run.

    As for the leading edge, I can offer no explanation. The prop was initially sharper. It was always run in clean water and never touched bottom of any type.

    This prop has probably 15 hours running time at about 3000 prop RPM and 60 MPH. I never noticed any loss of performance.

    Unfortunately, My Ballistic 21 pitch runs about 600-1000 engine RPM less (I forget the exact number) and still delivers the same top speed so this prop rarely gets used anymore. Personally, I am a big fan of Ballistic props however, the lower unit thrust washer needs to be replaced with a split shaft collar on Chrysler/Force engines in order to get the necessary exhaust snout clearance to use these props.

  16. #16
    Senior Chief Petty Officer emilsr's Avatar
    Join Date
    Dec 2010
    Location
    El Paso, TX
    Posts
    773

    Default Re: Sharpening edges of prop blades?

    Current theory is that a smooth (polished) surface doesn't perform as well as a matte finish. Much the same theory as why PWC racers sand the hull.

    Cavitation can be caused by many things, including blade shape. The only time I've experienced significant cavitation "burn" is running cleaver props on our old knee-knocker race boats. They would cavitate a lot getting on plane, and we'd often see burn marks...but that was extreme circumstances. I've occasionally seen the same thing on some modern high powered/high drive height boats with other styles of props, but not nearly to the same degree as with the cleaver design, and in these cases the prop slip was caused more by ventilation than cavitation. I suppose a sharp leading edge could make a difference, but there are other factors at play and simply sharpening the leading edge wouldn't, in and of itself, cause a cavitation problem.

    Prop design has come a long way since the early 80's.

  17. #17
    Fleet Admiral Texasmark's Avatar
    Join Date
    Dec 2005
    Location
    N. Texas, USA
    Posts
    9,398

    Default Re: Sharpening edges of prop blades?

    Quote Originally Posted by Frank Acampora View Post
    102_6374.jpg102_6373.jpg102_6372.jpg104_7083.jpg104_7082.jpg

    Well, Mark: I don't know if Chrysler ever had Michigan teflon coat their props but it does stand to reason that they might. When I had this prop repaired, the fellow who did the repairs remarked that where he removed the coating, the stainless underneath was not polished but rather it appeared to be sandblasted. Additionally, the parts of the blades where the coating has worn or peeled or otherwise failed to adhere, the surface looks the same. Logically, if I were going to apply a coating such as teflon or even a powder coat, I would ensure a good surface with a lot of "grab." This particular coating is glossy like powder coat but I don't think they had powder coating technology in the early 1980s (The approximate year of this prop).

    These two photos hopefully show the glossiness of the coating. One also shows where an aluminum tag with "Chrysler" silkscreened in red was applied. This tag blew off the first run.

    As for the leading edge, I can offer no explanation. The prop was initially sharper. It was always run in clean water and never touched bottom of any type.

    This prop has probably 15 hours running time at about 3000 prop RPM and 60 MPH. I never noticed any loss of performance.

    Unfortunately, My Ballistic 21 pitch runs about 600-1000 engine RPM less (I forget the exact number) and still delivers the same top speed so this prop rarely gets used anymore. Personally, I am a big fan of Ballistic props however, the lower unit thrust washer needs to be replaced with a split shaft collar on Chrysler/Force engines in order to get the necessary exhaust snout clearance to use these props.
    Frank,

    Got some Pics.

    First shot is blade edge for the other guys talking about thin blade edges. Flash obliterated dial caliper reading but .000" is at 6 O'Clock, .100 is at Noon, and the reading is 0.041".

    Next is a shot of the smooth leading edge

    Then The prop ID

    Next some scratches which were on one blade only and the result of low water (Texas drought) and some !@#$%^&* throwing a 6x8x16 cinder block in the water near the ramp which I hit in F at about 1000 rpms.

    Last pic is just a side shot showing some of the above, the distance the 24P puts the blade tips aft, the thickness of the blade front to rear, and one of the 1/4" ports I drilled in it to help my hole shot.

    I Never heard of the brand. I bought the current rig with one on it. It was a 17P and with me running this 24 XL prop (in my avatar to show the match), obviously the previous prop was a neck snapper in the hole shot. For the life of me I don't know how the previous owner ran this boat with that prop and why the dealer sold him the rig with that prop. He did it for 2 years.

    In buying this prop, they are not very popular and iboats had some in stock on a close out and had this sucker priced at about $290 and I couldn't resist. I have not been sorry.

    Regards,

    Mark
    Attached Images Attached Images
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

  18. #18
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,373

    Default Re: Sharpening edges of prop blades?

    I wouldnt deny there might be some benefit to sharpening the blade i actually shaprened the leading edge of my out drive... Very carefully mind you no file file was used..however while shaprening i had a hellof a time with the drive wiggleing back and fourth actually quite a bit as much as a inch. So the mind wander's and suddenly you realize when your at WOT your drive is slightly deflecting either to the right or left..it has to that slop under that much pressure is going to find where there is no play....It's called crabbing and id be willing to bet 3-5 mph is lost depending on how much your leg scew's.....A bit like a dog legging car...

    http://www.mercuryracing.com/_media/...Boat-Terms.pdf

    crab, crab Angle - An oblong object, such as a boat or gearcase, moving ahead but
    not directly in line with its longitudinal axis. For example, the slight angle to the left or
    right that the gearcase is moving in relation to the water flowing past it. Most
    pronounced with an elevated engine installation and surfacing type propellers. The
    term can also refer to a boat when its bow is not pointed directly in the direction of
    travel, such as in a turn or in a strong side wind.
    Page

    Now carry one....
    Stickly a opinion your milage may vary.

    Speed is how fast you hit the wall
    Torque is how far you move the wall"

  19. #19
    Chief Petty Officer jimbo_jwc's Avatar
    Join Date
    Dec 2010
    Location
    Dover Oh.
    Posts
    466

    Default Re: Sharpening edges of prop blades?

    Some guy way back invented a screw it could pump water , move solids ,gases , keep tolerance's around O.D. increased efficiency ,made pressure and heat . As I see it on my props we don't have pipe around our props so any thing less than square edges would spin water out and not push thrust strait back since they are submerged . Seen videos with bubbles around outside edges so props can compress water enough to get air from under water .Lets start a Thread with how many props do you have ad pics description .I have always filled out nick and only ones ever sharpened were on plastic trolling motor to cut weeds better and old Johnsons have reverse type looking props.

  20. #20
    Fleet Admiral
    Join Date
    May 2009
    Location
    Norfolk
    Posts
    9,568

    Default Re: Sharpening edges of prop blades?

    Back to the original question: I can't see how sharpening a prop on a recreational boat could make any appreciable difference. There are way too many other factors, from biminis to how much gas is in the tank. But you are making the prop unreasonably dangerous for people to be around. I'm not talking about serious injury from a running motor; I'm talking about ordinary stuff like bumping a bare foot against it while swimming/boarding, or while its on the trailer sticking out. Even in neutral, props spin.

    for the same reason, file off sharp nicks.

    And as for stupid questions--I used to agree there were no stupid questions, until I joined this forum. Here, I've seen a few. Yours is not one of them; it's a very good question.
    A man of constant boat tinkering.

  21. #21
    Petty Officer 2nd Class
    Join Date
    Apr 2009
    Posts
    118

    Default Re: Sharpening edges of prop blades?

    Thanks everyone for the opinions. It sounds like I'd have a hard time noticing any performance gains by sharpening them. The idea of just smoothing out any dings or bends and removing the least amount of metal seems like the best way to go. Thanks for the help.
    Verne

Similar Threads

  1. Propeller Size BF45, 4 blades to 3 blades...?
    By Jarle in forum Prop Questions and Topics
    Replies: 7
    Last Post: May 11th, 2007, 09:27 AM
  2. Propeller Size BF45, 4 blades to 3 blades...?
    By Jarle in forum Honda & Tohatsu/Nissan Outboards
    Replies: 1
    Last Post: June 10th, 2006, 04:29 PM
  3. prop blades
    By imported_bjs in forum Prop Questions and Topics
    Replies: 5
    Last Post: January 29th, 2006, 02:29 AM
  4. sharpening prop
    By DSL DOC in forum Non-Repair Outboard Discussions
    Replies: 2
    Last Post: June 8th, 2003, 02:16 PM
  5. Sharpening the blades on a standard prop
    By Skiboy in forum Yamaha & Suzuki Outboards
    Replies: 2
    Last Post: April 23rd, 2002, 06:59 AM
  1. iboats Forum Directory - Over 100,000 forum posts organized by topic