Why 4 blade prop

[OnEyeJack]

More is usually better. Why don't I see more 4 blade props around ?
What would I gain with a 4 blade prop on my large, under powered pontoon boat ?
does the blades factor into the pitch required ?

Thanks, love the forum
1 i

 

[alldodge]

More is not always better, ask the folks getting a months worth of rain in one day :facepalm:

More blades provides more lift, having a pontoon is not going to help.
More blades take more HP to turn, so you can reduce your slip which pushes the boat a tad farther with each revolution, but then the motor cannot turn the same rpms

Everything is a trade off

 

[superbenk]

4-blade provides more torque which gets you going faster (faster to plane, more control at low speeds) but the extra blade causes more drag which tends to drop top speed slightly.

I went from a stock aluminum 3-blade getting ~53MPH tops to a stainless 4-blade & dropped down to ~48-50MPH tops. But my low end control improved significantly & it runs a bit smoother.

4-blade is better than 3 for sports too (tubing, skiing, etc.) where the low end torque is a benefit over speed.

 

[superbenk]

Also, plan to drop pitch 1-2” if transitioning from 3 to 4 blades due to the added bite & drag. The drop in pitch is necessary to keep the engine WOT RPMs in spec. A good prop shop should be able to help with specific advice for your boat/engine setup.

 

[ahicks]

More is usually better. Why don't I see more 4 blade props around ?
What would I gain with a 4 blade prop on my large, under powered pontoon boat ?
does the blades factor into the pitch required ?

Thanks, love the forum
1 i

The little bit you stand to gain on the average pontoon boat is so small I doubt seriously you would ever notice it.

 

[jetboater]

Look on Mercury’s website—they specifically say their 4 blade Spitfire (or equivelent Quicksilver Nemesis) is their best prop for pontoons.

I’ve been running one on my current pontoon for the last 6 years (a Premier 25 footer) and on the Sanpan before that.

I think they’re a great choice for pontoons—-great low end torque and run very smoothly. Im not too worried about top end speed (after all, its a pontoon!) so a 4 blade is perfect for me.

 

[Leardriver]

The more blade surface, the less slippage. Think of a 4 blade prop as 4 wheel drive for your boat. The penalty is drag. At the top end, you will lose a little mph. That's is often a good trade off.
The manufacturers want to publish a high top speed for bragging rights and marketing purposes, so they use a 3 blade.

 

[groovy_moon]

Just went from a 14.5" X 19" 3 bladed to a 14.5" X 17" 4 Bladed on my Sea Ray 175. Will NEVER go back to a 3 bladed. Should have made the switch the day I brought the boat home the 1st time

 

[dingbat]

Can't generalize when it comes to props. The number of blades is just a small part of a prop attributes. A good stern lifting prop will perform as well, if not better, than generalized 4 blade prop coming out of the hole any day of the week.

I ran a 4 blade prop for a number of years because of the hole shot. Didn't like the amount of slip (21+%) it was giving me at cruise rpm and figured there had to be a better way.

Went to a vented, "performance" 3 blade prop. Between the vents and the stern lift the prop provides, the hole shot is superior to that of my old 4 blade and it increased the top end by 2-3 miles per hour. On top of that, fuel consumption decreased by roughly 6%.

In the end, the 3 blade was faster, provided a better hole shot and reduced my fuel consumption. Remind me again why a 4 blade is better...lol

 

[Sea Rider]

Just went from a 14.5" X 19" 3 bladed to a 14.5" X 17" 4 Bladed on my Sea Ray 175. Will NEVER go back to a 3 bladed. Should have made the switch the day I brought the boat home the 1st time

Just for the record, can you specify both wot rpm achieved with both props as usually loaded to read if there was a small or large amount of rpm difference. For me 3 blade props all the way...

Happy Boating

 

[Scott06]

Use what work best for how you use your boat, which I think is very individual. I would second the comments regarding stern lift.

For me I just got through trials of a 4 blade vensura, 3 blade enertia, and 4 blade revolution 4 . Best holeshot was with the vensura, but had high slip at wot, enertia performed well but gave up too much holeshot , though it gained 3-4 mph top end. The Revolution 4 surprised me. Since it bites better holeshot suffered a little compared to the vensura as the engine couldn't spin up as fast. Stern lift was the best of all three but was able to trim out more and actually gave highest top speed of the three. I didn't expect huge ability to trim out with the rev 4, nor the lowest slip (12%) of all three. Will see if going up in vent plug size helps holeshot. Very different results than I expected on top end with a 4 blade

 

[groovy_moon]

Just for the record, can you specify both wot rpm achieved with both props as usually loaded to read if there was a small or large amount of rpm difference. For me 3 blade props all the way...

Happy Boating

WOT with the 4-bladed is ~4500 spec is 4400-4800

WOT with the 3-bladed... I don't really know since I never really ran it wide open with the 3 bladed

Suffice is to say I am very happy with the 4 bladed. In fact, instead of repairing the 3-bladed I might just sell it for a few $$$'s and buy another 4-bladed for my spare instead of spending the $$$ to repair a prop that is inferior in virtually every way

 

[Leardriver]

WOT with the 4-bladed is ~4500 spec is 4400-4800

WOT with the 3-bladed... I don't really know since I never really ran it wide open with the 3 bladed

Suffice is to say I am very happy with the 4 bladed. In fact, instead of repairing the 3-bladed I might just sell it for a few $$$'s and buy another 4-bladed for my spare instead of spending the $$$ to repair a prop that is inferior in virtually every way

Since you have RPM to spare, I bet you would REALLY like a 15 pitch 4 blade.

 

[Sea Rider]

Thanks GM, engine has + 300 wot revs to play with, going per one less prop pitch from current 4 blade one should put engine to rev close to or near max 4.8 K wot rpm range. Will better hole shot with slight top end speed loss if plan boating more loaded than last water test.

Happy Boating

 

[alldodge]

WOT with the 3-bladed... I don't really know since I never really ran it wide open with the 3 bladed

Then your comparing apples and oranges, no facts or analysis. Unless the testing is done its just guessing and innuendo, but I'm glad you are happy with what your have