4 blade props

Tim M · 22 April 2007, 09:55

I've been looking at various props on ebay.com for my Johnson 140 (same as suzi df140). I came across a number of 4 blade props. Are there any advantages with these? The prop I have is fine in terms of speed/load etc but I want to get another to use as the main and use the current as a spare.
My current prop is a 3 blade 14X17 aluminium jobbie....

Hightower · 22 April 2007, 10:22

I think the general rule about numbers of blades on a prop is that the more you have the better balanced it's going to be and that it gives you better acceleration (holeshot).

You will suffer at the top end though, as props with more blades are less efficient. I dought that you will notice any or much difference with your setup though when comparing 3,4,5 bladed props with the same pitch and diameter!

Simon B · 22 April 2007, 21:25

Other factors for going to a four blade prop are;

1. Gives higher torque, effectively giving you more low end grunt.
2. Is useful if your boat will be carrying heavy payload but you still want it it to plane.

Ezgoing · 23 April 2007, 21:00

Tim

i changed to a four blade prop on my previous boat and loved it for the following reasons:

Better acceleration
Better mid range fuel economy
Better grip in foul weather
Better all round when carrying heavier loads
Slightly slower but not noticably, at WOT.

I am experimenting with props for the new booat and have not finalised decision yet.

Rgds

codprawn · 23 April 2007, 21:04

My 4 blade stainless is great - the acceleration is awesome but I think a 21" would be better than the 19" I have at the moment.

Jon.esp · 23 April 2007, 21:18

I curently have an aly 3 blade and am thinking of a 4 blade ss
can anyone recomend a prop suplier.
There are quite a few usa websites but I cant find anything local.

Roy Smith · 23 April 2007, 21:45

steel developments seam to know just about any thing to do with props

Tim M · 24 April 2007, 07:57

Ok so it all sounds quite positive. Should I get a 4 blade with the same pitch as my current 3 blade?

Jon.esp · 24 April 2007, 10:45

Thanks about the steel developments I will call them.

Do you find SS has an overall performance advantage over Aly. They say it is should as the baldes can be thiner. Is the diference noticable.

Tim M · 28 April 2007, 09:45

Quote:

Originally Posted by Tim M

Ok so it all sounds quite positive. Should I get a 4 blade with the same pitch as my current 3 blade?

I am on the verge of ordering now. Can anyone answer the above question?

Sounds like a 4 blade is the way to go....

Millermob · 28 April 2007, 10:08

We had one of the propulse adjustable 4-blade props on our honda 150, with the same pitch as the aly one we had on before we could barely make 4500 rpm, so adjusted it by one or two pitches and it was perfect, we only lost 1 knot off top speed and fuel consumption was amazing, 15lph at 25 knots.

It might be worth looking at these as we could adjust in 2 minutes depending on load etc.

Tim M · 28 April 2007, 10:11

At the moment by budget is only for one off ebay which seems to rule out something adjustable. I'm really liking the fact everyone seems to have seen their fuel consumption go down

Just need to know what pitch to get....

jwalker · 28 April 2007, 10:40

Quote:

Originally Posted by Tim M

Just need to know what pitch to get....

Tim, it seems to me the choice is; get a fixed pitch and take a chance, you'll be lucky to get it right, or wait for an adjustable one on which you will be able to set the pitch to correct.
Is it essential you have it right now?

Tim M · 28 April 2007, 10:41

It is rather as my present one got dinged....

jwalker · 28 April 2007, 10:48

Propulse

Tim M · 28 April 2007, 10:54

That would be ideal but it won't fit my engine (or will it?). Mine is a Bombadier Johnson (a suzuki df140) not an OMC...

Millermob · 28 April 2007, 11:38

http://www.tnorrismarine.co.uk/propulse.php is where we got ours from, might be worth giving them a call.

http://www.propulse.se/ on the 'fits to' section it looks like you'll need the 8902 model, at least when you ding it you can replace a balde

Tim M · 28 April 2007, 11:54

They're a lot cheaper than I thought they'd be. Problem is they don't seem to do one for my engine

Back to the ebay 4 blade idea....

Can anyone give me a rough idea of what sort of pitch would be suitable given my current 3 blade. There must be some sort of rule of thumb to go by

BruceB · 28 April 2007, 13:48

I tried 3 qand four blade props on my 60hp Yam through Steel dev and after bseveral trials on both blade sizes and pitches couldn't get a stainless to perform as well as the Yam 3 blade alloy one I had, so gave up.
I need a new prop soon and was curious about two things, do you change the pitch without removing from outboard and do people rate these propulse props?

vince · 28 April 2007, 15:17

TimM : 'I am on the verge of ordering now. Can anyone answer the above question?

Sounds like a 4 blade is the way to go....'

Hi Tim, this should answer your q, if your existing prop is the right pitch for the manufacturer, then go for the same pitch but in 4 blade. A 4 blade will drop around 50-100 revs at the top end, so if top revs aren't reached with existing prop, go for next pitch down. More info here: http://www.marine-outboards.com/choosing-propeller.htm