3 blade props Vs 4 blade props ???

[wlin88]

hello everyone

I am new to this forum and its by far the most contents fishing forum.

thinking about replacing my prop on the boat now just wanna get few opions from the gurus.

what is the main different and benifit between the 3 blade prop and 4 blade prop ??

thank you

[cormorant]

The extra blade

[wlin88]

thanks mate and the benifit been ???

[STUIE63]

what size boat?
what size outboard ?
what do you hope to gain ?
is your current prop the correct one?
what is your intended use ?
what is the max revs for your motor ?
what are the max revs you are achieving ?
what speed are you achieving by gps ?
all these questions will help to get a better answer
Stuie

[FNQCairns]

Brass tacks....physics says most efficient prop has but one impacting edge. The more blades a prop has (impacting edges) the less efficient it's design can EVER be.

Some 4 blades are more efficient that some 3 blades but if both props are designed to an identical specification then 1hp input into the 3 blade will deliver more work done than 1 hp into the 4 blade.

Now the model becomes application based......on heavy boats that do not run on the last 1 foot of their planing pad/plank the 3 blade rules supreme for all round efficiency.

For boars that are light and have hp outputs high enough to allow great bow lift, tiny running surfaces and engine heights measured in just mm from the centre of the propeller shaft then 4 bades/5 blades even allow greatly more constant contact per revolution with the water surface.

4 blades on slow boats (just about all of out boats) offer greater muscle due to the increased surface area over the entire propeller for blade design and compared to equivalent 3 bladers.

No one who runs a 4 blade on their slow boat (our boats) are getting the efficiency that they could be getting from a 3 blade...the physics do not allow for this while the earth still has gravity anyway but they may see better trim angles so better rough water handling etc, more bite at all times, better turns....just overall better handling....it's just they will be travelling slower for rpm and using more fuel especially once the engine has planed proper the boat.

[DAZMC1]

The extra blade

Why even comment with sarcasm. The guy,s new and just wants a civil answer!

[gr hilly]

i agree F N Q has given him good advice as usual,good onya F N Q
cheers Hilly

[Steeler]

Personal experience on a variety of boats inc 4.6 h/cabs 5.1 h/cabs and a V16R all powered by Merc inline 6's the 4 blade was always my preference.Without any shadow of a doubt the V16R was the most improved with the 4 blade.

4 Blade better holeshot,quicker to plane and better economy ( i am not a speed freak ).If your donk is reaching its ideal rev range with your current 3 blade be advised to drop back a pitch as a 4 will cost you a couple of hundred revs.

As a general rule a 4 blade will not provide the same top end speed by a few MPH and in my cases i mean only a few MPH's.

With all my boats and engine changes the first thing changed out was the prop to a 4 blade.I am in the process of rebuilding a 4 cyl 115 Merc and as soon as its done a 4 blade will find its way onto it.

Oh and if anyone has a 2+2 dead merc kicking around please PM me i need some plastic external powerhead bits.

Hope that helps.

Steeler

[myusernam]

gives you a lot of stern lift. makes the boat ride more horizontal. good for holding the plane.

[Hornet Rider]

Hi mate, welcome aboard. Have a read here, interesting stuff http://www.ausfish.com.au/vforum/sho...er+685+4+blade

cheers, HR

[Blusta]

Agree with Steeler and myusernam in my experience though not sure about the fuel economy comment. On my boat I found the 4 blader slower at the same revs which meant I ran it at a little higher revs to scoot along at the same speed; thus a lower top speed. Definitely more lift, instant pick up and an ability to hang on at lower revs. 'Tis my limited experience with the four blade prop.. I was comparing 19 inch 3 blade with a 17 inch 4 blade.

[trueblue]

You typically need one pitch size down in a 4 blade compared to a 3 blade.

My 3 blade vs 4 blade ends up with just about the same top end speed.

4 blade is great for everything in crappy choppy water, 3 blade is better for fuel economy and performance in calm water. Thats on my boat though. all boats are different.

cheers

Mick

[trueblue]

The extra blade

gold mate, absolute gold.

[dodgyone]

Personal experience on a variety of boats inc 4.6 h/cabs 5.1 h/cabs and a V16R all powered by Merc inline 6's the 4 blade was always my preference.Without any shadow of a doubt the V16R was the most improved with the 4 blade.

4 Blade better holeshot,quicker to plane and better economy ( i am not a speed freak ).If your donk is reaching its ideal rev range with your current 3 blade be advised to drop back a pitch as a 4 will cost you a couple of hundred revs.

As a general rule a 4 blade will not provide the same top end speed by a few MPH and in my cases i mean only a few MPH's.

With all my boats and engine changes the first thing changed out was the prop to a 4 blade.I am in the process of rebuilding a 4 cyl 115 Merc and as soon as its done a 4 blade will find its way onto it.

Oh and if anyone has a 2+2 dead merc kicking around please PM me i need some plastic external powerhead bits.

Hope that helps.

Steeler

A 16r and not a speed freak? You dont know what youve missed.

[Steeler]

I wish,but my 6yr old daughter would start pooping herself whenever i opened it up.