Another Prop Question: 4 Blades VS. 3 Blade?

Carl

Carl

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Cabelas has 4 Blades Solas high thrust props to fit my Nissan 18 2 stroke.
Stock prop on it is a 3 blade, 9.2 Dx 8.8 pitch.
The Solas are 9.5"D x 7 or 9 Pitch.
Does anyone see any advantage to going to a 4 blade prop?
Will I have more power under load or speed?
Any reccomendation on pitch when going from 3 to 4 blade?
I may be moving up to a heavier boat next year (1542 or 1548) and an wondering if I could consider keeping my 18 hp if I go to a 4 blade prop or some other different prop. Dont want more speed, just power to get a heavier & wider boat up on plane.
Thanks!
 
Carl, my experiance with 4-blades is, that they give you more hole-shot with less rpms on motor,do you have the "stingray or whale tail on the outboard" this will help tremendously getting up on plane, smaller number of pitch on prop=more rpm better hole shot,than on plane faster,bigger number on prop slower hole shot,more speed on top end,if that makes any sense,when you have a heavy load,as almost all duckhunters do getting up on plane is crucial,the four blade would make a big differance on your rig. I hope this helps Brian Rippelmeyer
 
Carl, what Brian said is true. More blades equals more thrust. You may loose some top end speed and even get some washout in high speed turns. Your stearn end will ride a bit higher with the 4 blade prop. For what we are doing more thrust will usually win out over top end speed. Good luck................Kevin
 
So woud you recommend going with the 7 pitch on the 4 blade?
Do I need to worry about exceeding the max rec. RPMs with a smaller pitch prop? Guess I need to invest in a tach!
 
Carl, Iwould go with the smaller pitch,more power out of the hole to get the rig on plane,is the 18hp a 2-stroke? I would not waste the money on a tach,I would place a whale tail on back though. Hope this helps Brian Rippelmeyer
 
Carl I am glad you started this thread. I had the same question, but I have a displacement hull BBSB. I know my top end speed is limited, but would I have notice any difference in overall performance b/w the two props? thanks. James
 
JS, your hole shot or getting on plane distance will be shorter with the 4-blade the smaller motor needs all the help it can get, the boat will come out of the water easier and not as many rpms on the motor. What size of motor are you using? Hope this helps, Brian Rippelmeyer
 
On small motors, you won't see any benefit with a 4 blade prop.






Q: What is the advantage of a 4 or 5-blade prop as compared to a 3-blade?
A: Most boats are equipped with a 3-blade prop from the factory. A 4-blade prop will usually give a boat a little better low-end power and handling, but often results in some loss of speed. A lot of bass boats with high horsepower will do fairly well with a 4-blade prop, especially with the new designs that are out now. Most inboard/outboard boats do just fine with a 3-blade prop, unless they are lacking on horsepower. 4-blade props do better when running close to the top of the surface, and most I/O's are running deep enough that a speed loss is common because of the extra drag. The 5-blade props are almost strictly a ski prop, where the low to mid-range pull is of main importance.
 
Lee is right.
Unless you have a tach you will be guessing at loaded RPM. And if the "Top End" is what you are worried about you can burn up your motor with it over loaded with too much pitch, IE wont turn up to rated rpm at the loaded weight of the boat as used. Called over wheeled.
You also own it once you test it. Props can hold a world of performance gain but must each be measured at the load(full of duck hunters and decoys ect.) and hull in use. No rule of thumb.
 
Sounds like two lines of thought here, one says it will be helpful, another saying it wont be a big difference and may over-rev the motor.
Guess I need to chat with Cabelas about their return policy on props before I decide to test one out. Any it mightbe worth getting a tach. They are pretty cheap compared to a blown powerhead.
 
Carl, your owners manual should have some guidelines in it for propping. Also, if you look at your motor specs, it will say something like "18hp @ 5500 rpm" or " wot @ 4400-5500rpm" this means you want your motor to be able to achieve this rpm pushing the load you have. Overloading the motor will "coke" it up with carbon and can cause cracked rings or worse, a run away motor that you can't shut off because of white hot carbon deposits stuck on the head acting like sparkplugs. That is a scary sumbitch as you sit and listen to your motor hit 13000rpm before chunking a rod through the side of the case. I watched a video of it somewhere on line a few years ago. I'd say start with the stock prop and see how it pushes the load then if it seems doggy, go down two pitches. Remember to use the stock one for fishing when you take your 300lbs of duck gear out.
 
It's really helpful to have a tach to know how your outboard is performing. Especially with small boats, adding 300 pound can add a lot of drag. Check out Tiny Tach: http://www.tinytach.com/tinytach/gasoline.php

On my bluebill with a 15hp Yamaha I use a standard 3 blade prop in the summer and a 4 blade prop during duck hunting season. I don't know how much of the difference is due to 3 vs 4 blades--it's probably due more to the difference in pitch between the two props--but there is a notable change in performance between the two.

Rick
 
Midwest has a prop with 4 blades & same pitch/diameter as my stock prop. How would that effect performance vs. stock 3 blade prop ??
Thanks guys!
 
You want a 4 blade prop so bad you can taste it...buy it and let us know how it works! ;) all being equal you will get a bit more drag with the extra blade.
 
That is what i was thinking, more drag cause its the same prop with just more blades to push through the water.
Dont really want a 4 blade, just looking to get the most out of my 18 under load. Do they make a 5 blade??? :)
 
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