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Old 01-20-2010, 05:55 PM
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Default Advantages of 4 blade over 3 blade prop.

I am looking to purchase a 4 blade 23 pitch prop, or the 3 blade 23 pitch mirage. Both sets are used but in perfect condition and will be powering a 28 foot 5000 pound center console hull with twin merc 250 efi's. I am leaning towards the 4 blade for better fuel consumption but dont want to lose to much top-end, what do ya think?
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Old 01-20-2010, 06:35 PM
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I lost 3-4 mph switching to 4 blades, but the pros outweigh the cons. I had to go from 21's to 19's when I switched. 26' Cape Horn with twin F-250's.

Pros:
Better Docking
Plane at lower speed
Better throttle response in s$%#tty seas

Cons:
Lower Top end
1 more blade to screw up if you hit something

The prop gurus will be along soon, they are much more in tune with this than myself.

Give Ken @ PropGods a call, Good People! Good Luck!
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Old 01-20-2010, 07:18 PM
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I've got 4 blades on a twin 200 optis, they have great grip in corners and excellent throttle response and I don't see much if any loss in top end.
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Old 01-20-2010, 07:22 PM
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I lost top end and fuel economy with 4 blades. For boats with lots of power I don't think there is a better prop than the Merc Tempest Plus (3 blade).
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Old 01-20-2010, 07:41 PM
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My buddy and I have identical boats except his has a Ford and mine a Chev. Both go exactly the same speed. I have a 23 Mirage Plus, he has a 22 Bravo 4 I believe.
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Old 01-20-2010, 08:00 PM
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I bought a set of the 23 mirage off here and was going to replace the lazer 23's I have now. Everyone seemed to love them. Ended up having to close the torque holes on the bottom of the props with the plugs and I've noticed most everyone else I see with them has also. They were spinning out and would not grab with the twin 250's I had. Holes are huge. Their cheep to buy the buttons and close them up but that totally killed the hole shot so I sold them to the guy that bought my efi motors and went back with the lazor for now until I get the 21p 4 blades I want. Fountain does not even install three blades any longer and I know the hole shot will be better but no slipping while in curves or turning is a huge plus. The bravo 21p 4 blade they said I needed with the 225's is all they run and I think i'm only about 500 pounds more than you are at 5400 with the 31. Suppose to drop one pitch number from the 3 blade down to 22p when your dropping from a three blade to a 4 blade or 21 since I'm not sure they make a 22 4 blade. The bravo blades are huge. I"m trying to sell a set of 17p Bravo's now and I can see why a 21 would be all I need from a 23p on the three blade. Photos are on the for sale page.
If you stick with 23 four blade from what I understand its going to knock your top rpm down about 3 to 5 hundred. Everyone on here dreams this prop god and he might be the one to check with before getting those 23 4 blades then not being happy with them. Fuel for thought.
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Old 01-20-2010, 08:55 PM
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Not always the case , but if sized correctly the switch to 4 blade from 3 can substantially increase low to mid rpm thrust for quicker plane-off, especially with more POB or extra gear. Better for towing boats skiers or tubes. Possible noticeable reduction in I/B vibration . Less unintended variation in rpm when running in seas either direction.

The add'l drag of the extra blade usually reduces WOT speed.
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Old 01-21-2010, 04:44 AM
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Some boats like mine (heavy single powered) need a 4 blade prop. Even now that I have plenty of power the 4 blade is much better to plane and handling (reverse) around the dock is much better. My prop slip numbers at cruise are much better with the 4 blade also. I'm more concerned with performance from idle to cruise speed and best economy rather than trying to maximize wot with I would never use.
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Old 01-21-2010, 06:22 AM
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I switched from 3 blade 19's to 4 blade 17's on my two f225's and I didn't see the reduction in top end that everyone else seems to experience? I did pick up much better response out of the hole and at mid-range.
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Old 01-21-2010, 11:29 AM
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Here is a link to an older post on the same general topic:

http://www.thehulltruth.com/boating-...stainless.html

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Old 01-21-2010, 12:23 PM
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Quote:
Originally Posted by TinManMike View Post
I lost 3-4 mph switching to 4 blades, but the pros outweigh the cons. I had to go from 21's to 19's when I switched. 26' Cape Horn with twin F-250's.

Pros:
Better Docking
Plane at lower speed
Better throttle response in s$%#tty seas

Cons:
Lower Top end
1 more blade to screw up if you hit something

The prop gurus will be along soon, they are much more in tune with this than myself.

Give Ken @ PropGods a call, Good People! Good Luck!
Mike Did you move your motors up a hole with the 4 blades... I tried 19 rev 4s and didnt like them at all... planed at lower speed.. didnt see any stern lift (which is what I was looking for) and shifting the boat in gear was awful.. only lost 2mph on top end but no better fuel econ.. only used them 1 trip and sold them..
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Old 01-22-2010, 04:44 AM
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Quote:
Originally Posted by TinManMike View Post
I lost 3-4 mph switching to 4 blades, but the pros outweigh the cons. I had to go from 21's to 19's when I switched. 26' Cape Horn with twin F-250's.

Pros:
Better Docking
Plane at lower speed
Better throttle response in s$%#tty seas

Cons:
Lower Top end
1 more blade to screw up if you hit something

The prop gurus will be along soon, they are much more in tune with this than myself.

Give Ken @ PropGods a call, Good People! Good Luck!

Mike want props are you you running? I am running 22 pitch Bravo 1's on my 31 CH and turning 5700RPM LOADED and 5900 RPM light. I do plan to raise my motors when I get time, and figure out how to get them off the boat. Capehorn put them on with 5200!!
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Old 01-22-2010, 06:26 AM
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I found the following when switching from 3 blades to 4.

1) Holds plane at lower speed
2) Holds its bite in rough water where the 3 bladers would blow out
3) Better overall fuel economy
4) Slightly lower top speed.
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Old 01-22-2010, 08:10 AM
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Quote:
Originally Posted by ScarabChris View Post
I found the following when switching from 3 blades to 4.

1) Holds plane at lower speed
2) Holds its bite in rough water where the 3 bladers would blow out
3) Better overall fuel economy
4) Slightly lower top speed.
I have to agree with Chris...my twin F115's with 3 blades were not doing well in anything over light chop. These aluminum 4 blades have done basically as well as can be expected....
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Old 01-22-2010, 08:44 AM
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I went from Lazer 23- 3 blades to Bravo I 22 - 4 blades. I wasn't getting the hookup I needed offshore. The Bravo I's solved the problem. I didn't loose any top end.

At the time the smallest Bravo I 4 blades were 22's. It might still be that way.
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Old 01-22-2010, 01:23 PM
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A 3-blade with long swept blades and extra cupping will accomplish much of the same advantages of a 4-blade. I put a custom Baumann 3-blade prop on a tunnel hull and got better holeshot than the Merc SS Trophy 4-blade that was on there - top speed remained the same, but engine rpm increased into the recommended operating range. Oh, the Baumann prop was cheaper, too ($375 delivered).
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Old 01-22-2010, 02:20 PM
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If you are fishing the weedbeds offshore and get them wrapped in the prop, the three blades will chop/rip it up and blow through, four blade you will need to clean it out and will act like you have no traction at all.
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