Holes in propeller?

titaniumneck

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Does having the holes, on the side of the propeller under the front of the blades really help increase your hole shot rpms? And if it does help, what size holes on a 40 hp s/s prop.
 

flyingscott

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Yes vent holes can help quite a bit. If the holes are too big the prop will ventilate to much to small and they won't make a difference.
 

Scott Danforth

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About 1/4" ti 3/8" range for a 40hp. Start small and gradually increase the diameter
 

Texasmark

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+1 on both answers. Size matters. I liked to get about a 1000 rpm boost at hole shot with ports vs without. So I adjusted the size till that's what I got. Since HP is (torque x rpm)/5252 and in the hole shot rpm range torque is linear with rpms, the faster you can jump your rpms the faster both will come up so it's AxB or HP exp2 effect. HP is what spins your prop shaft, spinning your prop which provides the necessary thrust.

Once you get on plane and up to speed, the water pressure running across your hub will seal off the ports and your engine will load up like they weren't there. When that happens the prop takes a good bite and you can expect your boat to lurch forward (somewhat) as the engine rpms drop with the load.

What it does for you in Bass Boats for one, is to allow you to run a high pitched prop for dazzling straightaways yet get your lard-arse transom heavy boat out of the hole in short order. It's like having 2 completely different props. I loved mine and played with it every chance I got.

Hey Scott, on this subject and "What's behind you doesn't matter".......Can't believe Enzo said that as his 6 cyl opposed hot dog that made his cars the rockets they were WAS BEHIND HIM, as is one's outboard and prop. Grin
 

Scott Danforth

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I believe he made that comment about rear view mirrors on racecars
 

jimmbo

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The holes allow an engine that is weaker in torque at low rpms to rev up to where it has enough torque to accelerate with a prop that has enough pitch to keep it from over revving. Years ago it was very helpful on engines like the OMC 49.7 cubic inch 75hp, and the Mercury 99.8 cubic inch 1500. Both of these engines were putting out 1.5 hp/cubic inch, and weren't the strongest engines at the bottom end.
Today, I guess the 4 strokes need all the help they can get to increase hole shot.
 
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titaniumneck

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I appreciate your help, I will try with 1/4 inch holes to start. I was just kinda concerned because everything I read on Internet said for 17 pitch props and up. I just took this 40 Tohatsu off my aluminum 15 foot flat bottom and placed it onto a 15 foot sprint fiberglass boat that I rebuilt, got it nice and shiny with all wood replaced. I needed the v hull because of my neck and spine issues. I have no power tilt and trim, but once it would finally get on plain it ran at 27mph which is fine by me, it ran at 30 mph on the aluminum boat. The prop pitch is at 12 now, 10 1/4 diameter. I'm going to put the holes in the prop and try it today.
 

walleyehed

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Yeah, start small...personally I'd start with 3/16" hole on 1 blade only, then 2, then 3. If you get to 3 and you still don't like it, go 1/4" all 3. then 5/16'
You can get too big too quick on that size of prop.
 

Texasmark

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I was just kinda concerned because everything I read on Internet said for 17 pitch props and up.

My guess on that is that the higher the pitch the more noticeable the change. Shallow pitch props are work props so you are already doing the work. A high pitch is usually for light fast boats that don't require a lot of work so you need to get some work out of them when in a working environment....the hole shot.
 

jimmbo

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Personally, I think venting the prop on a 40 is a waste of time and effort, but it's not may call.
 

walleyehed

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Jimmbo, we run 25hp on 12ft tunnels,(70+mph) with complete over-hub props (total vent) just to get on plane. HP/weight is proportional. 40hp on a 14ft light-weight or 250hp on a 22ft rig, doesn't matter.
 

Texasmark

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This is what it was like when I was a teenage spectator. Lots of 3 pt hydros too with 10 hp (average) too. Tiny little 2 blade bronze props with hurrendous pitches on 1:1 Quicksilver racing lower units were the norm.

They called it "getting over the hump" back then. Today it's the "hole shot". On the 3 pts, they had a spring loaded single throttle control. Squeeze and the little prop would squirt water, release, squeeze-squirt with boat gaining speed, etc etc etc, finally over the hump and away they went.

The guy in the cowboy hat is none other than Roy Rogers, VP of Yellow Jacket boats at one time. Lots of pictures associated with this one on the www....just google Roy Rogers and Yellow Jacket boats. He liked to race, lot of pics of that, and ride his 6 kids (with Dale Evans his movie star wife) around in his 16' Yellow Jacket with his 60 )when the first 6 cyl Merc came out and 70 hp later on "towers of power". I know he wore his cowboy boots most all the time but I just wonder if he had his spurs on too while racing? Who knows. Grin

That's a 25 Merc Hurricane in the pic, green alum cowling, first 4 cyl Carl (Kiekhaefer) built after his highly successful twins....see Chinewalker's Avatar for a racer.

http://www.pellegrinmarine.com/image...%20rogers).jpg
 
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titaniumneck

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Hey peeps, I forgot that I had a 11 pitch aluminum prop as a spare prop for the 40 hp, but before I came back and reread the new post, I drilled 3 - 1/4 inch holes in the aluminum prop, hopefully if my neck and back will cooperate and go try it today. One thing I forgot to mention is that with the twelve pitch s/s prop even after on plan, the rpms were lower than they were supposed to be. Besides the material, with everything equal what are the performance differences between aluminum vs stainless steel?
 

jimmbo

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When you say equal, meaning same blade shape and thickness as an Al prop, there will be no performance increase. the heavier weight might even slow the engine down a bit. But you would have a very strong and durable prop. The increases in performance with stainless came about because of thinner and better blade design allowed by the stronger metal. A Drop in rpms when switching to a SS may be because of the better blade design has a better grip on the water where the AL might be losing its bite.

I will acknowledge I have no idea what boat you are putting your 40hp on, but if you are racing, it is likely you would be running an over hub prop, not a thru hub. In most cases a 40hp is not going to benefit from a vented prop.
 

Texasmark

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When you say equal, meaning same blade shape and thickness as an Al prop, there will be no performance increase. the heavier weight might even slow the engine down a bit. But you would have a very strong and durable prop. The increases in performance with stainless came about because of thinner and better blade design allowed by the stronger metal. A Drop in rpms when switching to a SS may be because of the better blade design has a better grip on the water where the AL might be losing its bite.

I will acknowledge I have no idea what boat you are putting your 40hp on, but if you are racing, it is likely you would be running an over hub prop, not a thru hub. In most cases a 40hp is not going to benefit from a vented prop.

All of the above with one added big plus.......alum props, Turning Point's Hustler excepted, are usually NOT cupped whereas SS props normally ARE. Cupping makes a big difference in prop "bite" and performance. With that comes lower rpms due to the extra load on the engine, but if your rig benefits from the change, your lower rpms will bring you higher speeds....about 1 mph is the tossed around the site number but it depends on your rig. Gotta compare apples and apples when comparing props. TP Hustler is the closest thing on the market (opinion I have one) to SS except for the material. However their alum is of superior quality and that may allow them to thin out their blades somewhat over conventional run of the mill alum.
 

jimmbo

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OMC/BRP has been cupping their AL props for the V6 outboards and I/Os for decades.
As for what I think of Turning Points props... They make what looks like a decent blade design, but their quality control leaves a bit to be desired. I opened a few of their products boxes, and found a couple props that had 2 blades with one rake angle and the third with a different rake angle.
 

Texasmark

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OMC/BRP has been cupping their AL props for the V6 outboards and I/Os for decades.
As for what I think of Turning Points props... They make what looks like a decent blade design, but their quality control leaves a bit to be desired. I opened a few of their products boxes, and found a couple props that had 2 blades with one rake angle and the third with a different rake angle.

I stand corrected sir. Those engines are/were out of my league. I boat in the lower hp ranges, 125 and below. My experience with TP is one prop. I didn't mike it out but it looked good and ran smooth, nice prop for a hundred bucks.
 

jimmbo

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Jimmbo " I opened a few of their products boxes, and found a couple props that had 2 blades with one rake angle and the third with a different rake angle."

To clarify. The third blades were bent outward in the middle of the blade and it was easy to feel the difference in contour/shape, which changed the rake and pitch of the blade.
 

walleyehed

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Jimmbo " I opened a few of their products boxes, and found a couple props that had 2 blades with one rake angle and the third with a different rake angle."

To clarify. The third blades were bent outward in the middle of the blade and it was easy to feel the difference in contour/shape, which changed the rake and pitch of the blade.

I have heard of this but never seen one.. Was it (they) replaced no charge?? Did they have anything to say as to why it was that way? Interesting..
 

jimmbo

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I wasn't buying it, I just was looking at them. Found one bad, looked in a couple more boxes and found a second. I have run OMC or Merc Props for the last 20 yrs. I did run a 3 blade Stilleto on my outboard as a loaner for a month. It was OK, almost as good as the RAKER, but I ordered a RAKER.
 
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