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Propeller change 3 blade or 4 blade?


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If it's just hole shot you can plug vent holes on your prop.

The kit is $10.  And if you experience blow out a prop ring might help.

Basically a rubber band fits on prop. 

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Dog out of hole, blowing out are all just hard on your engine. The correct prop should plane your boat at max operating weight and top speed should be just below your max rpm.  

Think of it as the difference between a tractor and a car. The 4 blade will move more water meaning heavy loads can be negated so if you load up for camping, pull toys or have 4 adults they make it so

Finally got the boat out on the water.  Results are increased my speed by 3 mph.   I like the handling at speed,   So far happy with the reults

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Hey gang, this is a great discussion and I appreciate all the input on something I know nothing about. I am interested in your opinions on my situation. I will preface by saying some of the terms being used here are not familiar to me, so I won't use the terminology that most of you are, and if you could keep it simple for me that would be great.

I have a 2009 16' Lund Rebel XL SS. 50HP Merc. I bought it used and it came with a 4 blade on. I also have the original 3 blade, and I have always wondered if for my usage, I should switch back to the 3 blade?

75+% of my usage is on Lake O/E downrigging. So... run out to where I want to fish as quickly as I can, troll all day and then run back in to the launch. Not usually at full speed given there's usually too much chop on Erie to open it up. 

Usually have myself and one other person with me, have 2 downriggers- weight wise I would say medium... I'm not loaded down to full capacity at all. 

Performance-wise, I think its good, but I have nothing to compare to. My only complaints/issues are: 1) Its sometimes challenging to get the trolling speed quite as low as I want to in the spring. I am often shifting weight in the boat to try to get it down another 1-2 tenths of a mph, and 2) At top speed on flat water, it  does cavitate occasionally when turning sharply. This isn't a big deal or anything as I know when it will happen and I adjust to avoid it, but I'm not thinking I should have to?

So... there you go, thoughts? Should I leave the 4 blade on, or switch to the 3 blade? And for either one, why?

Thanks in advance for any help!

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I am running a 2019 Alumacraft Competitor 205 Tiller that has a 115hp VMAX SHO. 

I switched the standard yamaha 3 blade 17p aluminum to a 15p 4 blade Mercury Nemesis Aluminum. To be honest I haven't lost any speed, 37-39 mph in the right conditions.

I experienced a better hole shot and handling. These are not a overly expensive prop and hub kit to try :) 

 

 

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Thanks for the quick feedback. I know I can switch it out and test. And no, switching isn't a big deal, but I guess what I was looking for was expertise on if the 3 blade would be expected to help or hinder my two issues. I don't get out on the water very often, so figured there was no need to bother with it if conceptually it was obvious I would be going in the wrong direction. 

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2 hours ago, Grangb2 said:

Thanks for the quick feedback. I know I can switch it out and test. And no, switching isn't a big deal, but I guess what I was looking for was expertise on if the 3 blade would be expected to help or hinder my two issues. I don't get out on the water very often, so figured there was no need to bother with it if conceptually it was obvious I would be going in the wrong direction. 

No amount of expertise is better than an actual on water test.

If I was thinking of buying a prop, I would seek advise.  If I already had the other prop I would just try it out and get actual results.

  

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You can think of blades on prop as grip, 3 blade less grip little faster, 4 blade more grip slightly less speed ,5 way more grip than 3 .

What will grip do for you . For hole shot more grip will get you on plane quicker but you can over do it and bog motor.

When on plane like erie and Ont that grip will help when you need to go (mountain of water).

If your prop blows on holeshot it will defiantly blowout in big waves.

I don't know 50 hp market all my experience is 150 up .

to prop a boat you need your standard load 2 people downriggers  drink cooler rods tackle everything that you take on lake.

Then you need good holeshot and at max throttle to be just under the max rpm for your motor.

If you have it right you can never over drive your motor.

 

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On 4/1/2020 at 12:29 PM, Grangb2 said:

I have a 2009 16' Lund Rebel XL SS. 50HP Merc. I bought it used and it came with a 4 blade on. I also have the original 3 blade, and I have always wondered if for my usage, I should switch back to the 3 blade?

I got an email today because I was using the sizing app they have on their site.  They said that three blade props perform better for motors under 120 hp.  According to them the better hole shot etc., from four blades only applies to motors over 120 hp.

I also have a 16' boat with a 50 hp Merc.  So, I am interested in hearing how your boat performs with the two different props.  

  

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I put a 4 blade on our underpowered 60hp legend 16ft and was night and day difference.    Same  on our underpowered 20ft legend 115hp   stays on plane at much lower rpm and much better holeshot.   Beware around docks your first time with a 4 blade reverse is different. 

Edited by Freshtrax
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Don't get too caught up with # of blades. Find the prop that allows your motor to reach "peak" RPM at WOT. Whether it be 3 4 or 5 blade. Pitch and # of blades will change hole shot, stability and top end speed to slightly different degrees. Your motor and hull will influence each other differently day to day based on weight distribution and wave conditions. When you are out of the RPM range you'll notice one day your 3 blade will feel perfect but the next it will feel like it's pushing water and not moving the boat like it should. If you are under powered or over propped you will really notice when trying to maintain cruising speed in chop. But I don't think your rig is under powered.

I went down from 3 blade 17 pitch to a 15 pitch for my 40 HP etec tiller. Hole shot is now truly amazing. I'm on plane and cruising at 25MPH in under 10 seconds even in chop.  Top end speed at WOT is 2 mph lower than before but  RPM is right where it should be for peak HP.  I can back the throttle from max RPM to about 90% and cruise 2mph under my max speed. The extra 300 RPM I gained by dropping from 17 to 15 makes a world of difference when running close to top RPM. Before I could reach 31mph but only hitting 5400 RPM on flat water, I could never even get close to WOT in any kind of chop.  Now I max out at 29mph at 5700. And I can maintain that pace in chop no problem. 5400RPM gives me about 27MPh and 5000 around 25mph in most conditions.  So I generally cruise at 25MPH around 5000RPM and maintain tight handling and instant throttle response.  5000 would just get me over 25MPH on flat water before I switched. 5000 in chop wouldn't quite get to 25MPH and it was actually scary to hold onto the tiller arm LOL.

Now a full tank lasts forever and the engine never works hard, even when loaded and running at WOT.  Now all 40 HP is available. How much of my 40 was I getting with the 17 pitch??

Main thing is no matter which prop you choose, make sure that you are in the recommended range for RPM at WOT. If you aren't able to get to peak RPM at WOT then anything else is an experiment that makes your engine work harder and burn more gas.

You would probably get the all around performance boost you are looking for by dropping down a pitch.  Unless you are already hitting peak RPM. But I have a feeling you aren't. A 90 that's over propped wont be able to achieve 100% of it's HP. A properly propped 90 will have all of it's power available all the time. Tiny increments in throttle will push you further back in your seat and make your passengers giggle. Maybe your rig is set up near perfect and you are just striving for the ultimate sweet spot.

I hope you keep this thread updated with your impression of any changes you make.  Hopefully you find that sweet spot.

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A lot of tiller guys like 4 blade. They supposedly work well with stern heavy boats. I have a fibreglass ranger tiller with a 50 Yamaha running a 12 pitch 3 blade which works well it gives me 32 mph at 5800 rpm. I am going to try the same prop in a 4 blade 11 pitch to see how I like it. With me at 200 lbs plus 3 batteries and the fuel tank in the back I think the 4 blade might be nice. They recommend dropping in pitch when going to 4 blade to maintain your same rpm. Plus I like tinkering with stuff lol!

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I think you’ve got a handle on this already but here is my experience. 
 

went from a 24p raker HO to a 24p Raker RX4. Obviously not a merc but this is what I found. 
 

The RX4 has been a great prop for me. 
It lowered my RPM by about 200 (still raising the motor slowly to get its optimal performance), hole shot is faster and smoother, handling in turns is improved and no slip whatsoever. 
 

I haven’t lost any top speed  but I think that has more to do with me not getting everything out of the 3 blade than it has to do with anything else. Plus, I’ve raised the motor by about 1” so far and still plan on going higher 

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4 Blade was great for the hole shot but I lost 3-4mph on my top end.  Turn in was good, a lot more bite then the 3 blade I had on there.   Currently running a 3 blade stainless.  Best of both worlds if you ask me.  

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On 5/12/2020 at 3:30 AM, sauce said:

I went down from 3 blade 17 pitch to a 15 pitch for my 40 HP etec tiller.

Interesting.  I have 13" pitch on my Mercury 50hp.  Perhaps the E-tecs run lower RPMs or have a lower gear ratio at the lower end so they run a higher pitch prop at lower RMPs.

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I would have thought 15 pitch on a 40hp would be much too high also. I once had a Lund explorer with a 50hp mariner that came with a 14 pitch and I could only get about 5000 rpm. I dropped to a 12 pitch and it was perfect. But mine was a 4 stroke . With that boat I didn’t lose any top end speed it just got there much quicker. 

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With the 17, I was able to get RPM to just over 5400 tilted to the verge of porpoising. Recommended RPM for my engine is 5700-6000. Switched to 15 and I'm maxing out around 5750. I can really feel a difference when I'm cruising at 5000 and open it up all the way.  Fun!

I had it out on Wednesday. Found out I can plane out at 15 and then cruise at 12.  2500 RPM.

Getting my RPM closer to the recommended range definitely improved my motors overall performance.

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After reading the above, I started with a 10x17P  3 blade on a F40 tiller Yamaha/16' Princecraft.  Couldn't get it above 4800rpm.  Down to an 11 1/8 x 13P and got to about 5300rpm,  dropped it to 10 5/8 x 12P, now it will get to 58-5900 rpm without any struggle.  These are aluminum OEM.

Edited by Fisherman
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Got the 4 blade prop from Freshtrax (thanks) just little P.O &##%^^&^& that all local Boat Ramps are still closed!  Hope they open them up this week.

Sucks that the closest boat ramp is over 1.5 hours away right now. 

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