Polish prop...or not

[Wile E. Coyote]

A buddy of mine and I were sittin around and complaining bout how nasty my prop looked, and I said yea i'll get it polished up eventually and thus ensued the great debate I'll bring here now...OK racers OPINIONS WANTED In a drag set up two schools of thought. Polish the prop so it spins freely to rev quicker (theory) or leave it with the rough surface supplied by mercury so it gets more "bite" or "traction" to the water (other theory). I liken it to the same debate as polishing/roughening intake runners or velocity stacks to smooth/disrupt air fuel delivery however not being an expert I was just looking for any and all input, or I could just be completly insane with way too much free time. Thoughts????

[Jay Smith]

Mr. Wile,

I always liked the satin finish, I felt it bit harder, no facts to back it up just a theroy !And most agree that the bottom of a boat should be a satin finisn and sanded with 400 grit sandpaper , you would think the more polished ( shiney )a bottom the faster but thats not the case thats why I used the satin finish on the props. I have seen props in the past that was polished to chrome all over but 1" at the entire lenth of the end of the blade and it was bead blasted ! Go figure !:)

[Fl Boy in ILL]

I have a couple Tillman props and they are polished, I heared he says he can see flaws or cracks easier and quicker with a shiney finish and thats the way he likes to do them, I guess thats one train of thought.

Rick

[CompKing]

I just talked to John at DAH about a prop he's building for me.He likes to polish so any cracks will be easier to see.The differance in perfomance would be small but the safety factor in seeing a crack could be priceless.He said for the amount of time it takes if he didn't think it was important he wouldn't do it.

[Wile E. Coyote]

I like the discussion and the opinions are appreciated. It will mean ALOT in the way I work my prop!
Bill

[Ron Hill]

I'll add my thoughts here. Over the years, in kneeldown boats I've never seen a satin finished prop in the inspection area of the finals at an APBA Nationals. Usually, the props are thin as hell and sharp as a razor.

BUT, I used to make OPC props like that and they usually broke after not much use and that was in the 150 HP days.

I my onw testing, I believe a satin finished bottom is in fact faster than a polished bottom. Jay Smith said 400, but I like almost 80 grit...sanded long ways, which brings us to the question of satin finished propellers. I would not want the satin to go across the blade. I try to make the satin lines follow the rotation of the blade, not exactly but in that motion. I am convinced that Speed coat is slower.

The trailing edge is very important in how a props really runs. We, family relgion, always took a very sharp knife and ran it across the trailing edge of a blade to where there was a slight burr, just before a Kilo run or a Nationals final heat.

The slightest "EDGE" is what you are looking for in racing. Polishing, under a microscope, tends to roll off the back edge. But this can be sharpened back..

Bottomline, if the prop works, keep it...Polishing a satin fished prop could ruin it. Same as satin finishing of a polished props could ruin it. I take a machine polished Mercury Bravo One, thin it, balance it, sharpen the edges, and satin finish it and it picks up three mph and gets on plane faster. Nothing I did SHOULD make it plane faster, I wouldn't think anyway, except the satin finish.

Sand blasting or glass beading the trailing edges, to me, was done to cause the cup to "Slip". See, I believe cups slow props down......Anyone want to go there??

DeWald seems to own Formula One, his props are polished. Most Formual One dudes don't use Merc Props, but I've heard it is customer service (He loans you several to buy one). I've heard Mercury sells you one or several. When I've reworked DeWalds, the winningest one I did was satin finished.

Jim Boo has built some damn fast props over the years. His polishing is close to perfect.

All the above are my opinions. I guess that is what makes "HORSE RACE".

Bottomline: I don't know that there is an answer...maybe, I should run for politics!!!

[Barefoot Bob]

I had a thin blade Yamaha prop that was reworked here in Minnesota. The guy did a real nice job on the prop, and said it has been known for this prop to throw blades. After he re pitched it and re polished it for me, he dulled it up all the way around the prop. About a half inch in, all the way around. Said that this is done to divert it from cracking. And if I would nick it at all I should ruff it up again like it was. Never had to, the prop worked great.

Just thaught I would add this...What do you think:confused:

[Wile E. Coyote]

Ron,
Thank you very much for your input. The propeller I have now is an old mercury test prop and it has those very lines you are talking about, in what looks like 80 grit. the prop works just fine its just ugly (it was painted black and now its mostly not :D ) and so I do believe I will go with the old addage: it aint broke so I wont fix it.
Thanks
Bill

Bob,
I have experienced first hand the yamaha props cracking, I have done a little research into it and I belive that shotpeening the fillet area (where the blade meets the hub) will reduce if not eliminate this problem all togeather. I have a yamaha prop with three cracked blades, and as soon as I get the money to have it welded up and heat treated I am going to put my theory to the test. Ill post if and when I get results....

[Ron Hill]

I was pretty sure someone would want to see what I meant about the trailing edge. This knife, was made by my dad, especially for trailing edge "Skuffing". It also doubled as a cupping guage.. We used to smear lipstick on the props and then make a run...Never buy non-smear lipstick!!!

[Ron Hill]

Noitice my kneeldown props are polished... You can use a razor blade knife on the trailing edges, too...

[sho305]

Wow! What a great thread! I have sharpened all kinds of props and (rounded)LUs on stock slow boats, getting a gain every time from that blunt edge. I did note on my Laser II for my 1500 I had to cut out the trim tab to fit it(later put the backset one on...might have to remove it and see what happens) When I notched it I found one blade almost 1/8 longer than the other two, and that made me wonder about dynamic balance. I started to file it down, but then left it assuming they had balanced it maybe. Looks like they ground the back edge after polishing this prop at the factory. I am amazed at how few people realize the importance of a perfect prop for performance:confused:

[BRENT GILL]

Wile , the prop you talked about with 3 cracked blades is junk. Don't waste your hard earned money on those repairs because you will fling a blade and then you might be shopping for a lower unit and a prop.

[Wile E. Coyote]

I agree, however, I'm not really going to run balls out, the cracks are just begining, this is more of a personal experiment than anything else. The prop does no good just sitting there. I have had the opprotunity to tour Metal Improvement in Blue Ash Ohio, and talk with their engineers, I/We felt at the time that welding the cracks, re-heat treating and then SHOTPEENING the fillet area will add greatly improved strength characteristics, and may solve the problem.
I'll sight two examples, one is mine and the other is General Motors, GM was having a fatigue cracking problem on their deisel rocker arms on a certain motor, after x amount of hours they would crack and fail. They sent a sample to be shotpeened and have not had another failure, it is standard production procedure now. The second is mine, I completely trashed the carrier nut in my L/U, sent it out to be replaced, the shop in question did a fine job, but after less than 10 hours (hard hours) there were cracks developing around the welded nut/ lower unit interface, I had them re-welded and I shotpeened the area myself and so far (about 50 hours) not the first sign of failure...
Im not saying this is a cure all for all situations, but the if the cracking in these props is fatigue, and not harmonics, it is possible this will relieve the stress in this area making the prop useable again. Any way its worth my time just to see
Bill

[Ron Hill]

Generally a prop cracks because it is too thin, too old, too sharp, to hard or something. Generally, reparing them IS A WASTE OF EFFORT. Now, after saying that, I will say, I have "Fixed" some people's "Baby" by "T" welding the blade.

I grind a small flat spot, about a half an inch on the leading edge, weld the crack, then run a small bead down the leading edge. Then, I hammer the welds to make them dense, then only sharpen the weld down the leading edge. I do not remore all the weld or any material from the already thin blade. It looks like a patch, and it is a patch.... but sometimes it wll work... Many 14 1/2 Choppers, especially 28's had flaws or "Chills" in the middle of the blade, right where they teld to crack anyway... (Where the metal had cooled when casting and did not blend together)... welding these casting flaws, like I said, some are still running 15 years later...

Add: the "T" weld forces the prop to flex either in front of the bead or above the bead, but NOT on the crack...

Shotpeening makes sense to me, if you don't "Screw Up" the trailing edge by rounding it off...I have only shotpeened rods....

[airide18]

My opinion would be the satin finish.The smother the faster the prop less drag.:D

[mjwalters]

Ron We bought alu. and ss props from you when we still had custom marine in DE. A while ago ...... Any way what about cup? Have you run any surfaceing props with out it? I always thought the prop had to have it. Do V drives and hydros run cup?
Michael:confused:

[tabararacing]

Hey Ron, you already did the politics in APBA. Whats next for politics. Still waiting to try that prop out that you sent me. I got to talk to you some time. Please email me at brian@tabararacing.com. Thanks Ron,
Brian

[Ron Hill]

I'm never "Done" with politics, just "Cooling" my heels. My latest efforts have been toward an APBA Lifetime Achievement Award and establishing a new Division called "Best in Show'. Best in Show would include all OPC-Inboard-Stock-PROP-Mod Divisions plus Classic Stock-Antique Outboard-Classic Mod-Classic Inboard and Classic OPC. Each boat race would have Best in Shop as a part of the "Happening" and a National Points WINNER would be awarded in each Division..

[fasteddie]

You spoke of Jim Boo earlier in this post.Would that be Jim Boo of Precision propeller in Indianapolis Indiana?I have had some repair work done there and it was superb.I have always had dealings with Mark Croxton, who seems to be very knowledgeable.looking forward to having them do some tuning this spring.

[Ron Hill]

He's the ONLY JIM BOO I know. He's the nicest, most humble, honest, funniest and best prop man I know.I can't possibly say enough nice things about the who family....

His son, Chris, who we call "Turbo" spend a week with us about two years ago......by Saturday night he had to go to bed at 8:00, between me and my old boy, Chad, we'd worn his Indianapolis Ass out. Chris loved California, but I think he'll be in Indiana for many years...

ADD:

Mark is like "FAMILY" at their props shop... I don't know if they are as slow as they used to be, but took me about two years to get some props...but then it takes me that long to pay for them....

Last add: Spent a week at The Miami Boat Show about four years ago...Jim and I talked props for hours and hours. He always too care of Reggie Fountain and Benny Robertson...them Offshore Boys is still mad at Benny...mainly because he was so fast....So guys buy A set of props...Reggie buys 25 sets and send them to people for rework....

Last, last add: I used to make aluminum blow out rings for SJ's and FJ's, I thought they were cool....until I saw Jim Boo's stainless steel blow out rings.... We have a mutual respect, maybe because we both know how hard it is to make a truely great prop...

[Ron Hill]

I used to write the "prop Shop" for Western Bass, here is what I'd said, in 1983, about Turbo Props...feelings haven't changed...

[FCnLa]

Mr Hill, I have a Precision Propeller Turbo 14.25 X 22 I bought for my bass boat several years ago for $100. It is a beautiful prop and after what I have read here, I have to try it. The problem is it did not come with a thrust washer. Where can I get one? It looks like some one ran an OMC washer on it because of some grooves in the webbing. I did not want to take a chance on screwing it up, so I put it up.

Thanks,

Paul

[Ron Hill]

Email me your address, I'll send you one (Turbo washer)...

[Barefoot Bob]

I had a 24 Turbo on my boat back whan I had a 175 Rude on it. It was the fastest prop I had.

[AQUAholic]

I been having this "urge" to take one of my satin finished

choppers, cleavers, or ET copy's and run it. Than take it off and

bead blast it and try it again the same day.

Problem is it will look like crap and I will have to spend 2 hours sanding and re-polishing it again.

I cant see it making much of a difference, but then again who knows.

[airide18]

Thats alot of sandin on one prop in one day:)

[Ron Hill]

In the early days of MOD VP the 14" Chopper worked great. But we'd break the blades like popcorn. I started glassbeading some...which NEVER broke, but they were BUTT UGLY... and with the next season came, new hulls, new power, new props....we stayed with polish because I liked the looks...

With GPS timing a man might figure out the difference...ON my Bravo Drive I have a sating finish because that is what is "COOL"...

[Hebert519]

down here in texas we race our duck hunting boats. Mine is 14ft aluminum semi-v with a 3cyl 40merc on it. Ive had extensive motor work done and added trim. I was running a full polish cleaver that was sharp as hell and it was radared at 52mph. After a friend took sandpaper and roughed up the leading edges and bead blasted the trailing ones we radared it and it ran 54 all day long!!!!!

[Ron Hill]

Herbert,

I won't argue with the results....but, glassbeading the trailing edges can act as an increase in pitch, almost like more progession in the blade. If glassbeading the trailing edge helped, maybe you could still turn more pitch...

Just thinking..

[Hebert519]

youre right ron, i was running about 6300rpm, i just sent the prop to be turned up id like to be running about 5800.:D

[Ron Hill]

See, this is where it gets all screwed up...Because, if you had the "perfect" prop and glass beaded the trailing edges...

Somone asked about writing a Prop Book for Dummies... Hell, I'd need to read it too. I've always just read the speedometer...for awhile it was aradar gun, now GPS...

The answer IS TESTING.. When the Speedway would close for the night...Penske would fly his cars to Michigan to continue testing...even if they were fastest that day.

[Ally 1988]

I have a copy Yamaha 24 not sure who made it. But my question is are the welded together or are they forged then machined then polished or left what I will call a mat finish in my case. I love this prop for its wholeshot but I had it inspected today using a die penetrant and found two shallow cracks as I was told by the inspectors ( at work) they both seem to think this is a weld line. Me Im not sure anyway the (2) cracks are on the leading edge side in the transition area from blade to hub located about 1 1/2" from back of prop neither appear to to go any further than this one is about 1 1/4" the other about 1" they run along the transition area. Should I be concerned or have them removed then welded up then polished back down. Or just call this prop history. Sorry no camera hear or I think I could get a shot of its location anyway. Thanks for any help.

[Wile E. Coyote]

Ally,
That is where they all crack, mine has all three blades cracked. They can be welded, make sure you get the prop re-heat treated after. Most people don't fix them because they will crack again. It is the way they are made. way to thin in the area in question. Sorry

[Ally 1988]

Thanks a friend has one as well his has not been thinned out as much as mine has been and has not been used as much. So I guess Ill find another prop. Another question there was talk of having props bead blasted what type of material was used Glass, Ceramic, or Steel ?

[sho305]

I thought they used glass for beading.

[AQUAholic]

You can use all kinds of stuff.

Sand and ground glass id the most common.

I use ground glass, it actually looks like sandblasting sand.

[Wile E. Coyote]

Media, depends on what you are doing. Plastic, walnut shells and other soft media are used to strip paint from all types of surfaces
The more agressive like aluminum oxide and glass actually move metal around, glass is the most common and is most likely what is being used.
Bill

[Ally 1988]

media does move material around I work with Steel Shot Ceramic And Glass. Steel does the most as far as moving material around then ceramic then glass. But it depends on whats being hit. Titanium moves alot but Stainless changes the least that and Nickal. It sure would be cool to have a prop made out of titanium because of its weight. But the downside is the cost have you seen the cost of the new golf clubs and that is the recycled stuff we cant have that in the Aircraft industry but it is light.

[MirageMark]

Hydrodynamics suggest that a satin finish should be more efficient than a polished finish on props and here's why: A "rough" surface tends to keep the boundary layer attached, therefore creating less turbulence as the blade moves through the water. As a result, the prop moves faster through the water and ultimately allows for more rpm's maybe! This same concept applies to any object in motion through water and often the air. A smooth polished finish tends to break the boundary layer, allowing air to enter and increasing turbulence. This is all bad when you are talking about things moving through the water column. People think that fish are smooth, but the slime coat actually provides a microscopic rough layer allowing that boundary layer to remain attached. So, if anything, you should always try to emulate a fish, because after all, they have to be as efficient as possible, becuase they live in the water column. It's life or death and millions of years of evolution for them. Hope this helps. At the ODBA events, you will see both finishes. I would venture to say that you will see more satin than polish though.

Mark

[Ron Hill]

I'm making a bunch of new little outboard race props... I have NEVER done one with a Lab Finish. This group, I'm going to make several, exactly alike as possible...then satin finish some...This finish seems to be working, for me, on everything else...

[thaw ripper]

They are worth it ! A pic of Jeffs mean machine! It use to be in the family, my dads old boat he restored! It does fly, trust me!

[Stv Euro]

I am just getting into the high performance world of outboards and I have a couple of props that are polished. What and how is the best way to polish the props?:D

[Wile E. Coyote]

You mean to re-polish an existing prop just get a good quality metal polish. (met-l-prep or met-all) and go to it.
If you're intent on polishing a prop that has never been polished before there are two options. 1. send them out (this is most efficient!) after youve done one youll know why
2. strip all the paint (if there is any) and begin by choosing a grit of sandpaper that will remove all the surface defects (this is assuming your prop isnt damaged or dinged up too bad) usually 320 in wet/dry sand by hand until all you can see is the sanding marks from the 320. Move to the next finer grit (400) and repeat sanding until all the 320 marks are removed. Continue this process down to at least 800 grit (for a super fine shine go all the way to 1000) After that get U some metal polish (MET L PREP) or similar and polish until it shines!
This is very labor intensive and possibly dangerous to your hands depending how sharp the leading or trailing edges of your prop are. Good luck

[David_L6]

Ron,

How about telling us your thoughts on cup?

[Mark75H]

David, I saw Ron's thoughts on cup elsewhere. I'm pretty sure he said it wasn't that great of an idea; that cupping a prop was basically a bandaid that made up for some defeceincy.

Ron, I understand your point of view when it comes to cupping to increase speed by adding cup to affect effectivce pitch, but what about the effect cupping has on a prop's ability to maintain a good bite in turns? Can you really make a prop that goes fast and doesn't blow out with no cup?

[Ron Hill]

Big cups, with cold Coors Light is great... 44Ds are big cups, too.

If you're playing catcher their damn important...

Truth be told, cups are needed, usually, but I don't see them increasing speed, if everything is "TOGETHER"... You need a "TRACE" of a cup, you can't have fade away....

[Ron Hill]

Call my 900 number, it is $45 bucks a minute...

Not really Sam...Weigh to power is a term I've used all my life and what I mean is that a 10 HP on 400 pound boats...the props doesn't matter...2000 HP on a flat bottom, the prop doesn't matter unless it turns the boat over when you jump on it...

I've so many races in my life time with CARY Props, I could not count all of them...And cup a Cary or a Record and you'll lose speed and general performance.

My friend used to play a one string guitar... he said,
The rest of them SUM BITCHES is looking for it, I've found it." He wasn't much of a guitar player...and to say you own one prop and that is the answer, is like playing a one string guitar...

In theory, and I know the difference between theory and practice, when you slow for a corner, that is when you'd want a prop to slip and keep you R's up... What ever racer looks for is a shifter prop...one that picks up RPM's as soon as you turn the wheel and winds all the way around the corner, then shifts when you straighten the wheel. Any J or A driver that has ever been fast know shifter props are where it is at... In larger classes it is harder, but they are around!!!