4 Blade Prop

Jono Garton · 26 May 2006, 18:02

Any one used a four blade prop?

Anygood?

Dino · 26 May 2006, 18:10

Hi Jono
I had one on a honda 90 on a 6mtr rib,i thought she used to over-rev(4000rpm at 23knots)but it wouldn't redline(30 knots at 5500 rpm)
so i don't know if that helps but i found it strange.It also aerated as easily as a regular prop through corners on that particular rib.I wouldn't pay for one!

codprawn · 26 May 2006, 21:48

Got a 4 blade 19" on my boat - obviously not a clue what it is like YET but from the sea trials the acceleration is supposed to be awesome. Top speed was 41kts but it is a very fine pitch - should be about 21" or even 23".

Will post some details ASAP!!!

Ezgoing · 26 May 2006, 22:24

Jono

I was using a standard yamaha 13 3/4 x 19 Yamaha three blade.
After much consultation I have just purchased a 4 blade 13 3/4 x 17 four blade Solas prop in stainless steel. I am told it will:

Give better grip in the rough stuff
Give better accekeration
Handle the heavy loads better(i often carry 250 ltrs petrol)
Slow down my top speed a little.
Conserve fuel by approx 10%

I will be fitting it for the run to Scotland next weekend and will let you know.

rgds

Charles · 27 May 2006, 10:06

Quote:

Originally Posted by codprawn

Got a 4 blade 19" on my boat - obviously not a clue what it is like YET but from the sea trials the acceleration is supposed to be awesome. Top speed was 41kts but it is a very fine pitch - should be about 21" or even 23".

Will post some details ASAP!!!

As usual, everything you write about is hearsay, read somewhere or 'someone told me'. Why don't you gain some experience in a RIB and then base your assertions on fact! Blah, bla, blah!

codprawn · 27 May 2006, 12:59

Quote:

Originally Posted by ct01

As usual, everything you write about is hearsay, read somewhere or 'someone told me'. Why don't you gain some experience in a RIB and then base your assertions on fact! Blah, bla, blah!

And why don't you just......

BogMonster · 27 May 2006, 14:08

Not offering an opinion on 3 vs 4 because I know nothing about it, but ....

Most new engines I have seen advertised seem to come with a 3 blade prop fitted by the manufacturer. Is this just because it is cheaper to make, or is it because it does the best all-round job? A pretty competitive industry so you would think that the manufacturer would fit whatever gave them an advantage unless there is a big cost difference....?

Just my thoughts anyway.

LURCHER · 27 May 2006, 17:02

Here Here Codprawn , some people love to have a go at you for no reason , you liven up the forum and after all it is only your opinion !

codprawn · 27 May 2006, 19:15

Quote:

Originally Posted by LURCHER

Here Here Codprawn , some people love to have a go at you for no reason , you liven up the forum and after all it is only your opinion !

Thanks for that - I made it perfectly clear that I hadn't experienced the prop myself YET. In fact the person who told me was someone I respect greatly and is VERY experienced - Bob at Shoreline - Suzuki main dealer.

Still it is pretty obvious which people on here have the "attitude" problems!!!

FreeTrader · 27 May 2006, 22:55

I know I keep harping on about it. But we've just fitted a 5 blader to Quick Exit, and I can't argue with the results. We cruise at 34 knots at 4200 rpm, that's 600 rpm less, I'm saving stacks of fuel, and have achieved a better top speed of 46.2 knots (4 knots faster).

Also, we went out in a F8 on Saturday, and the drive, and grip was fantastic.

Surely more blades = more drive in the water?

Charles · 29 May 2006, 11:11

Quote:

Originally Posted by codprawn

And why don't you just......

Just what, show you up for the fraud you are? 4500 posts and most everything is hearsay and 'googled'!

Quote:

Originally Posted by codprawn

Thanks for that - I made it perfectly clear that I hadn't experienced the prop myself YET. In fact the person who told me was someone I respect greatly and is VERY experienced - Bob at Shoreline - Suzuki main dealer.
Still it is pretty obvious which people on here have the "attitude" problems!!!

You miss the point entirely 'bubble-boy' I did not challenge Bob's opinions (who I happen to know!) rather the way you purport to be a world authority on everything without having any actual personal experience.

Quote:

Originally Posted by FreeTrader

Surely more blades = more drive in the water?

Err, not quite! What pitch is your 4-blader? If you were to add one inch of pitch you will reduce full-throttle RPM up to 200. The same theory applies by reducing the pitch by one. A 4-blade prop generally reduces the revs by about 100 rpm.
There are a number of good reasons for going to a 4-blade prop, if you have a 3-blade prop - all of this applies to your set-up, application and various other influences. A 4-Blade prop generally increases acceleration, cavitates less and handles better in the mid-range. Its the upper range you should be concerned with. As you reach higher speeds the extra blade(s) have served their purpose and drag etc come into play. As has been mentioned a thousand times, prop selection is a 'black art' and the correct prop for your craft should largely be determined on your application. For long-range cruising at higher speeds I would not necessarily chose a 4 -blade or Hi5 prop. Horses for courses!

Simon B · 29 May 2006, 11:21

After advice we changed our prop from a 3 to a 4 as mentioned our horse wasnt right our course. Our boat is routinely loaded to near its stated capacity and we are not interested in top speed.

Having experienced the diffrences it gives our set-up the following advantages;

More torque - when fully loaded it still holds its RPM
It appears better on fuel but we didnt really have detailed figures previously
Doesnt get knocked off the plane as fast as the old one

Charles · 29 May 2006, 11:44

Quote:

Originally Posted by Simon B

After advice we changed our prop from a 3 to a 4 as mentioned our horse wasnt right our course. Our boat is routinely loaded to near its stated capacity and we are not interested in top speed.

Having experienced the diffrences it gives our set-up the following advantages;

More torque - when fully loaded it still holds its RPM
It appears better on fuel but we didnt really have detailed figures previously
Doesnt get knocked off the plane as fast as the old one

Makes sense! You probably did the right thing.

Seaharrier · 29 May 2006, 12:03

We replaced our 3 blade prop by a 5 blade prop.

Top speed with light load and perfect conditions remains the same (52.5).
Top speed with normal load (3 adults and 250l fuel) and normal conditions went up with (from 48 to 49).
Acceleration is much better + it's easier to reach the 45 kn bar and way faster to reach the top speed!
Fuel economy is more ore less the same.
Much more grip!
Planning at lower speed / RMP’s

Paul

Ezgoing · 14 June 2006, 22:18

Hi guys

Sorry I am so long in coming back but our local telephone lines were torn down by some kind trucker.

Regarding the prop change we got

Much better acceleration under full load
Maintain same cruising speed with lower revs( now maintain 30 knots @ 3800 rpm previously we needed 4200 rpm to maintain speed.
Boat appears to hold speed better in the rough.

Further feedback later

Rgds