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 3 blade vs 4 blade prop
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Author Previous Topic: Proper way to repair fiberglass on hull bottom? Topic Next Topic: Need help from Les and the other wise folks here  

PartsMan

RO# 29198

Posted - Feb 07 2008 :  08:48:02  Show Profile  Reply with Quote
I'm looking for a new SS prop. I have a 23 1/2" cuddy cabin w/ 5.7 and alpha one drive, that we mainly use for water sports. At first, I was looking at a 19p 3 blade SS prop, now swaying towards a 18p 4 blade SS prop. I want a good hole shot for the water sports, but like all men still want the top end. I've heard the 4 blade will cause you to lose a 1-2 MPH on the top end. But, you run at lower RPM at cruising speed and will save fuel.

Looking for some opinions, is it the 3 or 4 blade prop?

Homeport: Perry, Ohio

Perry

RO# 3836



Posted - Feb 07 2008 :  09:10:50  Show Profile  Reply with Quote
PartsMan,
Better hole shots, lower planning speeds, lost high-end mph. My buddy changed his 23' Maxum to a 4-blade and loves it.
Perry



Homeport: Shinnecock Go to Top of Page

Ponce

RO# 21119

Posted - Feb 07 2008 :  11:21:39  Show Profile  Reply with Quote
I had a 25 maxum scr with a 5.7 and put on a 4 blade (i Don't remember what pitch) It did plane the boat out nice, but I went back to the three blade because the prop seemed to loose it wash when making turns like pulling a tube or dodging crab pots. I did loose some top end, but I never ran that hard so it was insignificant.


Homeport: FL Go to Top of Page

KiDa

RO# 16492



Posted - Feb 07 2008 :  12:32:17  Show Profile  Reply with Quote
Trashed my Aluminum prop on my Regal (Volvo 5.0 SX) and replaced it with a Piranha 4 blade composite. Pickup up cruise speed, lowered GPH at cruise and all but eliminated the vibration associated with a three blade.

____________


Best Regards,

David
Saint Max
'99 330 Sundancer

==========

Capitalism is to this administration what Judaism was to the Third Reich.

-- Me

Homeport: Hopewell, VA Go to Top of Page

PartsMan

RO# 29198

Posted - Feb 07 2008 :  13:19:10  Show Profile  Reply with Quote
I'm new to this boating stuff ....

What do you mean, when saying "the prop seemed to loose it wash when making turns like pulling a tube" ?



Homeport: Perry, Ohio Go to Top of Page

Adjuster

RO# 29088

Posted - Feb 07 2008 :  17:42:08  Show Profile  Reply with Quote
I switched to four blade, one very significant benefit not yet mentioned and this will apply to a small number of boaters. Four blades give you ten fold increase in steering ability while reversing. I have to back out of my slip and now I can purposely steer anywhere I want to go instead of just meandering backwards at the mercy of the wind and tide. Also the four blade will lift the stern of your boat much higher out of the water even at low speeds while in forward. It is a difference you will immediately notice. My prop also 'washes' out at hi speed turns but my boat is more of a slow planing speed cutty cabin so I am rarely going fast enough for it to be a problem.

PartsMan, to put it simply 'washout' is the equivelent of loosing traction and spinning out your car ties. An air pocket forms around your prop and prevents it from getting traction in the water.



Edited by - Adjuster on Feb 07 2008 17:47:56

Homeport: Lighthouse Point Go to Top of Page

jimini

RO# 29250

Posted - Feb 07 2008 :  19:39:41  Show Profile  Reply with Quote
Adjuster~ doesn't your three bladed prop also washout at hi speed turns? Washing out means the prop is too close to the surface of the water or the keel is picking up air and delivering to the lower unit? which is the same difference for a four blade or a three blade prop isn't it?

jim "jimini" kennedy

Homeport: saugatuck, michigan Go to Top of Page

Adjuster

RO# 29088

Posted - Feb 07 2008 :  21:59:28  Show Profile  Reply with Quote
Hey jimini, no my three blade did not wash out. I believe the reason for this is with the three blade the stern of the boat and hence the outdrive stay much lower in the water. The four blade prop provides a significant amount of lift raising the stern out of the water and hence bringing the outdrive up to the waters edge. I believe this is why I am getting the washout in sharp turns at full speed. I highly recommend the four blade if you have an old heavy fiberglass hull with an I/O that likes to squat in the water. It leveled my boat out at plane, reduced planing speed and increased mpg. The improvement was immediate and actually amazing. Prop was delivered to my door for $130.00 made by 'Solas Propeller' the 'Amita 4' model. Best $130.00 I have spent on the boat.


Homeport: Lighthouse Point Go to Top of Page

jimini

RO# 29250

Posted - Feb 07 2008 :  22:09:57  Show Profile  Reply with Quote
I gotcha ya! Amazing what $130 will do isn't it?

jim "jimini" kennedy

Homeport: saugatuck, michigan Go to Top of Page

Type-A

RO# 24241

Posted - Feb 08 2008 :  10:44:38  Show Profile  Reply with Quote
I went from a Merc Laser II (19 pitch, 3 blade) to a Merc Rev 4 (17 pitch, 4 blade) on my Crownline 225ccr. 5.7 liter/Alpha 1. Another plus to the 4 blade is it takes out the pulsation that you feel with a 3 blade. It wasn't that noticable until I tried the 4 blade and then put the 3 blade back on - and both props were balanced.
If your drive is trimmed down/under you won't wash out (blow out) the prop.


Russ
Oshkosh, WI

2005 Cruisers Yachts 300 Express

Homeport: Oshkosh, WI Go to Top of Page

mikev324

RO# 29026

Posted - Feb 08 2008 :  12:07:47  Show Profile  Reply with Quote
OK...Here's the dumb question of the week!! Month...year...
I have a 24 ft Chris Craft cuddy...Volvo Penta motor 5.7 Gxi..and an OMC Cobra outdrive..How do I know what type/size prop to purchase????


'93 Chris Craft Concept
24'

Homeport: NY Go to Top of Page

stmbtwle

RO# 7934

Posted - Feb 08 2008 :  12:11:29  Show Profile  Reply with Quote
Do you have ANY prop now? If so what does it do with that prop? That will give us a baseline to work with.

Willie: Look Ma no paddle!

Homeport: Tampa Bay, FL Go to Top of Page

MrsRobinson

RO# 19626

Posted - Feb 08 2008 :  12:25:27  Show Profile  Reply with Quote
We have 4 bladed on our boat (twin inboards). Currently the 3 bladed ones are on while we wait for new 4 bladed ones to be cast. So this is the first time for me to run our boat with 3 bladed props. BIG difference getting on plane (twice the amount of time) and a BIG difference docking. The 3 bladed props do not 'bight' as nicely as the 4 bladed ones. She also cruises slower at idle speeds with the 3 bladed ones.

Greg
2001 Regal 3780
Twin Horizon 7.4

Homeport: Deltaville, VA Go to Top of Page

obeejr

RO# 16004

Posted - Feb 10 2008 :  21:01:55  Show Profile  Reply with Quote
Sounds like four blades are clearly better. Why then has no engine manufacturer put them on stock, if it is so much better? The OEM cost between the three and four blade has to be negligible.


Homeport: Greenwich, CT Go to Top of Page

KiDa

RO# 16492



Posted - Feb 10 2008 :  21:49:43  Show Profile  Reply with Quote
quote:
Originally posted by obeejr

Sounds like four blades are clearly better. Why then has no engine manufacturer put them on stock, if it is so much better? The OEM cost between the three and four blade has to be negligible.



Anticipate a minimum of 25% more for a four blade v. a three blade. More if on an inboard. Add a 5th blade and the price triples.

According to Mercruiser, the boat mfg determines which prop goes on the boat, not the engine folk. Now how that makes any sense on a Sea Ray, please explain it to me.

So the retailer wants to make as much money as possible they are going to put on the cheapest prop possible.


____________


Best Regards,

David
Saint Max
'99 330 Sundancer

==========

Capitalism is to this administration what Judaism was to the Third Reich.

-- Me

Homeport: Hopewell, VA Go to Top of Page

Adjuster

RO# 29088

Posted - Feb 11 2008 :  22:51:38  Show Profile  Reply with Quote
The engine and boat come as a package and then add the optional accessories. You need the total weight of the boat before you can prop it correctly. Even then the boat manufacturer can only install a general prop that gives a certain range of maximum rpm. The dealer needs to know the purpose of the boat, hole shot or top speed, number of regular passengers, fuel and water always topped or never topped off and many other variables before the absolute correct prop can be chosen for the buying customer.


Homeport: Lighthouse Point Go to Top of Page

Msibley

RO# 16534

Posted - Feb 12 2008 :  06:54:12  Show Profile  Reply with Quote
quote:
Originally posted by Adjuster

The engine and boat come as a package and then add the optional accessories. You need the total weight of the boat before you can prop it correctly. Even then the boat manufacturer can only install a general prop that gives a certain range of maximum rpm. The dealer needs to know the purpose of the boat, hole shot or top speed, number of regular passengers, fuel and water always topped or never topped off and many other variables before the absolute correct prop can be chosen for the buying customer.



Not quite.

To determine correct prop, you need to know what the wide-open throttle rpm's are for your engine. The best prop is one that lets the engine run nearest the designated WOT rpm setting as is possible.

1" of blade pitch change equals approximately +/-200 rpm.

Over-propping, meaning a prop that is too steep in pitch, will lug the engine and eventually damage it.



Mike
"War is cruelty. There's no use trying to reform it, the crueler it is the sooner it will be over."
"I hate newspapermen. They come into camp and pick up their camp rumors and print them as facts. I regard them as spies, which, in truth, they are."
- Maj. Gen. William Tecumseh Sherman, Commanding, Union Armies-Military Division of the Mississippi

Homeport: Melbourne, FL Go to Top of Page
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