What if anything would I notice from 3 to 4 blade prop

[KDAVID1]

I am looking for a spare prop. I currently have a 14" 25p on a Ranger 354v with 1993 Merc 150hp. Top speed 68mph rpm 5500. Would a 4 blade be safer. Not looking for more speed, gas savings, or hole shot just wondering what if anything a 4 blade would give me.

 

[Bifflefan]

Re: What if anything would I notice from 3 to 4 blade prop

I use a 4 blade exclusively on my I/O. I love them. I have a 3 blade spare and every once in a while I put it on to remind me why I dont like them.
To keep the same speed and such, use a 24p 4 blade.
In my experience, a 4 blade gives you better slow speed handling, less blowout when trimmed up, they go a lot straighter in reverse. I dont know why that last one is, but it does.
Others say you will lose a couple MPH with a 4 blade. This has not been true for me.

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

You think being an outboard v i/o would make any diff. from what you have seen with yours?

 

[Texasmark]

Re: What if anything would I notice from 3 to 4 blade prop

Yepper.

Every post I have read on the subject says the same thing as Mr. bifflefan said....but this is the first time I heard about the reverse part. The other thing that you can get is reduced vibration that you may not even know you have. For a given rpm, you have each. circle cut into 4 pieces rather than 3. Years ago Merc ran 2 blade props for the efficiency at higher speeds but had a lot of vibrations in the process. I think they changed over to 3 being the standard when they changed their paint from Seafoam white to Phantom Black Lacquer.

I/O's have a lot of weight at the transom including passengers who love to sit in the jump seats alongside the engine cover so I/Os would be somewhat more noticeable that an OB without those problems, but the extra control is still there. You can take some pitch out of your 3 blade and get similar type results with respect to slower speed control and more stability but you certainly will sacrifice top end (normally).

Mark

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

sounds good. Thanks alot.

 

[Jennifer "water-wolf"]

Re: What if anything would I notice from 3 to 4 blade prop

http://www.propgods.com/forum/default.aspx?g=posts&m=6639#6639
I just went though this experience myself, you can read all about it at the Prop-Gods forum above....Now I know why people refer to 3 blade aluminum props as 'clunkers'. EVERTYHING will be much better with a 4 blade, especially a Stainless, which is stiffer and stronger, and can be made with thinner blades.

Safe boating,
Jennifer

 

[QC]

Re: What if anything would I notice from 3 to 4 blade prop

Now I know why people refer to 3 blade aluminum props as 'clunkers'. EVERTHING will be much better with a 4 blade

Top speed won't be better . . .

 

[Jennifer "water-wolf"]

Re: What if anything would I notice from 3 to 4 blade prop

In my case top speed WAS better by 1 MPH. I have to admit this was not an apples to apples comparison, as I went from a entry level 3 blade stock Mercury 19P prop to a Mercury Quicksilver Typhoon 4 blade 21P stainless steel. Speed loss or not will depend on the slip ratio of each prop and the pitch. I still think he ought to consider a Solas Stainless 4 blade from the sales side of iBoats or one of the more expensive brands if he can consider that. A Solas Rubex would have been my first choice had I not found a pre-owned Typhoon at a good price. He may or may not loose a few MPH, but mid and low speed grip and stability should be much better. For ONLY going fast, then I agree with you totally 100%, and personally would be looking to find a superior engineered 3 blade, and not expect to gain as much in the handling, grip and feel that a good 4 blade will do in more normal speed ranges.
Jennifer

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

Thanks to all this helps alot. I still haven't decided which but I think I may be leaning toward 4 blade just to see. Stainless of course--wouldn't use anything else as they are very durable.

 

[zopperman]

Re: What if anything would I notice from 3 to 4 blade prop

Some things I've heard about SS -- they ARE stiffer and harder which means you will mess up your engine if you clunk somehting, whereas with an alum. it will more likely damage the prop then the drive/gimbal housing ETC... Just something to consider. But in general people seem to be happier with SS

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

Some things I've heard about SS -- they ARE stiffer and harder which means you will mess up your engine if you clunk somehting, whereas with an alum. it will more likely damage the prop then the drive/gimbal housing ETC... Just something to consider. But in general people seem to be happier with SS

Isn't that what the hub is for? Doesn't it slip?

 

[Dhadley]

Re: What if anything would I notice from 3 to 4 blade prop

SS props won't tear up the motor. If they did no one would run of fish shallow waters. I can assure you flats fishing is alive and well.

There are different kinds, models and styles of 4 blade props. Some are made for sterndrives, some for outboards. The outboards have a huge advantage as they can easily be raised to change the X dimension. We'll assume that the Ranger we're discussing has a jackplate, probably hydraulic. Generally speaking, a 4 blade will run at a higher X dimension especially with models built for outboards. It's not unusual to find the right 4 blade prop is faster than the best 3 blade, depending on hull style.

With the newer Rangers we find that the right 4 blade is much better overall but the fastest prop has been the Turbo Lightning or TXP. It all depends on set up and balance. And what the owner wants.

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

SS props won't tear up the motor. If they did no one would run of fish shallow waters. I can assure you flats fishing is alive and well.

There are different kinds, models and styles of 4 blade props. Some are made for sterndrives, some for outboards. The outboards have a huge advantage as they can easily be raised to change the X dimension. We'll assume that the Ranger we're discussing has a jackplate, probably hydraulic. Generally speaking, a 4 blade will run at a higher X dimension especially with models built for outboards. It's not unusual to find the right 4 blade prop is faster than the best 3 blade, depending on hull style.

With the newer Rangers we find that the right 4 blade is much better overall but the fastest prop has been the Turbo Lightning or TXP. It all depends on set up and balance. And what the owner wants.

Hmm--of course mine is a 1991 model so the hull is different from the current models--but something to think about. One thing--would a 4blade have more or less steer torque? Turning left (especially when trimed down) seems a little stiff.

 

[Dhadley]

Re: What if anything would I notice from 3 to 4 blade prop

Torque in the steering wheel is a product of set up. With the older Rangers we see the fastest prop as a 3 blade Turbo Lightning, a 4 blade TXP or Fusion 4 will probably be a tick slower with a light load but as fast if not slightly faster with 2-4 people and a 1/2 tank or more of fuel. Mid range and laod carrying ability will be better. Mercs don't have a lot of bottom end torque so the TXP 4 blade would probably be a better choice than the Fusion 4.

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

Torque in the steering wheel is a product of set up. With the older Rangers we see the fastest prop as a 3 blade Turbo Lightning, a 4 blade TXP or Fusion 4 will probably be a tick slower with a light load but as fast if not slightly faster with 2-4 people and a 1/2 tank or more of fuel. Mid range and laod carrying ability will be better. Mercs don't have a lot of bottom end torque so the TXP 4 blade would probably be a better choice than the Fusion 4.

Now I getting some where. When you say set up--is this height of the engine or trim angle? The way it is now I know I am trimmed proper when I get zero torque at speed. Should the engine be jacked up a bit more?

 

[wellcraft19]

Re: What if anything would I notice from 3 to 4 blade prop

Hmm--of course mine is a 1991 model so the hull is different from the current models--but something to think about. One thing--would a 4blade have more or less steer torque? Turning left (especially when trimed down) seems a little stiff.

KDAVID1:
For torque steer, you have to adjust the trim fin that sits above the propeller (under the anti-ventilation plate). On Mercruisers (assume it's still there even on the Mercury outboards) it is also the sacrificial anode. Adjust so you have no torque steer at the speed/trim you use the most.
Personally, I feel I saw more torque steer with the new 4-blade, but outdrive is not fully adjusted/trimmed yet, so a tad early to tell (can read about my experiences in a separate post). Went from 14x19" 3-blade, to Solas 14.5x17" 4-blade (should likely have stayed with a 19' pitch).

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

Interesting---do you adjust in the opposite direction of the torque?

 

[wellcraft19]

Re: What if anything would I notice from 3 to 4 blade prop

Yes, at least that is the idea.

On a "fixed" drive (straight axle, sail boat drive, etc), a RH rotating propeller will try to pull the stern to the right, turning the vessel to the left. On a stern drive, same principle, but since it'll "pull" (or rather try to to turn) the drive, the vessel will tend to turn to the right. This is due to water having higher density/pressure at the lower (deeper water) half of a propeller than at the upper.

So on a RH rotating propeller, the the prop will try to "move/turn/pull" the sterndrive to the right, thereby the boat will turn to the right. To prevent this, you adjust trim the little trim fin above the propeller in the same direction. The fin will then force the drive in the opposite direction, compensating for the force of the propeller.

So, in this case, you have to put force on the wheel to prevent boat from turning more and more to the right. Turning the trim fin to the right will help you reduce the torque steer.

That is at least in theory - and the way it worked on my 3-blade propeller. On my new 4-blade Solas, I actually had to adjust the trim fin a bit in the OTHER direction (illogical, but latest experience from being out this weekend)...

And, as you might have seen in my updated post, I went too far down in pitch when going from 3-blade to 4-blade (dropped 2" in pitch) and is now horribly under propped. Can easily reach 6,000 and only 26 knots, about 500-1,000 rpm too high, and about 10 knots too slow.

 

[KDAVID1]

Re: What if anything would I notice from 3 to 4 blade prop

Thanks for the info---this is the only time I have heard of this (but is all new to me anyway) about adjusting the trim fin (anode) other than in the previous post you made---it's pretty cool stuff.
Boy on the prop you really have a big swing their!! For me I think I will stay with the 25p on the 4 blade--I see where someone said to go with 24p on a four blade--but my speed and RPM are perfect with 25p and don't want to change that (loosing a bit of speed is no big deal--as this boat is fast enough for me--68 on GPS perfect conditions)

 

[hoopstoon]

Re: What if anything would I notice from 3 to 4 blade prop

some advise you need to drop a degree when you go three to four... read the Mercury prop selector site...