4 Blade Props

Postby PKB » Mon Mar 15, 2010 4:29 pm

Has anyone tried or run a 4 blade prop on a Lewis Prestige. I currently use a Lt2 3blade and were told by Lewis not to run 4 blade on them.

what is fuel consump like ?
did it help much out of the hole?
boat is used for skiing/wakeboading[if you could call it that LOL :lol: ]
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Postby mac_man_luke » Mon Mar 15, 2010 5:03 pm

We just stuck austral 4 blade prop on our Gilflite shortline 190 w/ 350 chev

We went from 12x15 3b to 12x14 4b

Fuel economy has been better, jumps out of the hole and holds lower speeds far nicer.

Used for kneeboarding/Wakeboarding/Skiing etc
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Postby sncaust » Mon Mar 15, 2010 6:19 pm

i have a lewis excel 1850 350 chev dog clutch and had an austral 1215
went to a lundberg 1214 4 blade.
Out of the hole is so much easier, on plane quicker
fuel consumption alot better due to less effort to get on plane
maintaining a constant speed is alot easier, only downside is i have
lost wake size, not that it was super big but definately noticed a
difference, just run a couple fat sacks now.
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Postby paulsal » Fri Mar 19, 2010 11:49 pm

4 blade prop on a Lewis Outback 2002 model. Usually doing about 18mph with wakeboards and about 25mph with the kids on biscuits. Great fuel economy and plenty of power down low. Unless you need more speed I would go for the 4 blade.
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Postby PKB » Sun Mar 21, 2010 8:29 pm

Thanks for the feedback will be putting one on over winter
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Postby Spud69 » Sun Mar 21, 2010 8:57 pm

also if u ur running over 300hp you should be running a 4 blade prop
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Postby Geckster » Sun Apr 11, 2010 8:56 pm

over 300hp? i've never heard that before. What's the reason for that?

How do 4 blades go at the top end, or are they only suited to boarding/skating?
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Postby AndrewC » Sun Apr 11, 2010 9:49 pm

I am interested in how it was said that a four blade prop cuts down the wake size. Is this a common occurance with all boats or just some. I currently am thinking of changing my 3 blader to a 4 blader too
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Postby sncaust » Sun Apr 11, 2010 10:27 pm

The 4 blade gets onto plane quicker and sits the boat flatter than
the 3 blade giving it less wake.

It wasnt much but noticably different, but in saying that the boat
now pulls out of the water so much better, can now fill it with fat sacs
have 5 people in the boat and still pull 2 100kg+ riders on on
wakeskates. Plus at riding speed is doing less revs, so less fuel.

Thats my experience and when talking to a couple of prop manufacturers they all say that it will loose wake but the benefits are worth it. I still have my 3 blade as a spare but dont htink i will take the 4 blade off in a hurry.
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Postby Geckster » Wed Apr 14, 2010 10:00 pm

sncaust, how does it go top end? whats your top speed compared to the 3 blade 12/15? similar?
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Postby sncaust » Thu Apr 15, 2010 4:58 pm

top end speed still the same, get to about (48mph on the speedo)
only thing that changed was the revs.....
Trying to remember which way they went (up or down) but was only by a couple hundred
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Postby ghind » Tue Apr 20, 2010 6:53 pm

You will find the Acme 3 blade props will give the best holeshot, midrange AND top end performance. They are CNC machined and have a surface like a golf ball. In addition they use more modern profiles than many of the local props.

Also, a 15" pitch prop is VERY tall to run on any 350 chev and not many 350 chevs have the top end to turn them.

A Rolco type 350 chev should be capable of at least 4400rpm at wide open throttle. If it isn't, it is labouring and you should change the prop. You wouldn't tow a caravan up a steep hill at 40kph in 5th gear and you shouldn't lug a boat like that either.

A Mercruiser will have the WOT rating visible on the engine. When the boat is lightly loaded, at full throttle it should turn the full rated RPM as shown. For example, if it says 4600-4800rpm then it should turn 4800rpm when the boat is lightly loaded or even slightly more.

If you use your boats with heavy loads, then you should go back even further in pitch. At your full ballast load, your motor should still be able to turn at least the minimum rated RPM eg 4600 in the above example. If not, change prop pitch.

Generally a 13" pitch prop is about the best for a 350 chev in a normal ski boat. Some people claim a 15" pitch prop is "better" or more economical or whatever but see the caravan example above and consider the manufacturer ratings for the engine.

The ACME and OJ branded CNC props are awesome but expensive. A 4 bladed prop may be better than your current prop but I'd be going with a CNC prop for sure

Greg
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Postby Skier1 » Tue Apr 20, 2010 9:08 pm

ghind thanks for a very informative reply on prop sizes and types,very interesting :D :D just checked my 315 hp Mercruiser and its WOT rating is 4600-5000 rpm. Full throttle is about 4900 rpm from memory.I have a ACME 13 x 11.5 CNC prop on it.
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Postby toecutter » Wed Apr 21, 2010 1:16 pm

Hey skier1 is that a 3 blade prop?
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Postby Skier1 » Wed Apr 21, 2010 6:30 pm

Yes it is a three blade.
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Postby ghind » Fri Apr 23, 2010 10:56 am

Skier1 your prop sounds spot on for your boat, what is your boat?

For a small 20ft ski boat a 13" pitch will generally be the maximum with a 315hp Mercruiser or 330hp scorpion. The "300hp" marinised 350 chevs can't be compared to this - unless your engine comes with a dyno report they are almost always VERY optomistic.

With a 270hp engine, about 12.5" pitch is more like it.

Many people run 15" pitch and their engines top out around 4000rpm or even less, even when the boat is empty and not pulling anybody. I'd never do that to my boat.

Greg
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Postby gotwake » Fri Apr 23, 2010 12:02 pm

On my Response i had a 3 blade, changed it to a 4 blade OJ and the holeshot was heaps better, it was always loaded and topend lost about 3-4 MPH but the wake seemed bigger.

And speed was way easier to regulate
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Postby Skier1 » Fri Apr 23, 2010 4:57 pm

ghind wrote:Skier1 your prop sounds spot on for your boat, what is your boat?

For a small 20ft ski boat a 13" pitch will generally be the maximum with a 315hp Mercruiser or 330hp scorpion. The "300hp" marinised 350 chevs can't be compared to this - unless your engine comes with a dyno report they are almost always VERY optomistic.

With a 270hp engine, about 12.5" pitch is more like it.

Many people run 15" pitch and their engines top out around 4000rpm or even less, even when the boat is empty and not pulling anybody. I'd never do that to my boat.

Greg


Greg It is a Lewis Eclipse.
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Postby toecutter » Mon Apr 26, 2010 8:05 am

Paulsal what is the dia*pitch of the 4 blader you put on your outback.What was the dia*pitch of the 3 blader you replaced.
Thanks m8.
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Postby ghind » Mon Apr 26, 2010 9:27 pm

Skier1 wrote:Greg It is a Lewis Eclipse.


I was going to guess Malibu Response LXI. From what you described the RPM range, you obviously had the idea prop. Being a 12.5" pitch it couldn't be a small ski boat but neither could it be a wake boat.

Regarding the 4 vs 3 blade prop, I have no doubt that a 4 blade prop will be better than most aussie boats 3 blade props supplied new but the ACME props are better again. The 3 blade ACME props will be even smoother, faster, more economical and have better holeshot.

They are CNC cut and have a finish on them a bit like golf balls. They are much more accurate - cast props tend to have between 0.5" pitch and 1.5" pitch difference between each blade on the same prop.

They are expensive but the right prop will make a boat.
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