3-blade vs 4-blade

[V4 Johnson]

I need to get a 2nd prop for my boat.

It's a 17 ft. 4 Winns with a 1984 115 hp Johnson. I am currently running a Michigan Wheel 3-blade 13 1/4" x 17 aluminum prop and it seems to be a spot-on match for my rig.

As I've been looking over all my prop options, I was kind of considering trying a Solas 12 3/4" x 17 4-blade aluminum. What are the advantages and disadvantages of the 4-blades?? If the pitch remains the same, will top speed also remain the same with a 4-blade??

Also.......what about the Comprop's?? Are they worth it to save a few $$ ??

 

[JaseBosto]

Re: 3-blade vs 4-blade

Also.......what about the Comprop's?? Are they worth it to save a few $$ ??

I had a few comp props in my day...they work fine but are useless after hitting anything, where as an aluminum will take a little abuse and a stainless will take a beating, but then again, something like a comp prop is good because you save your lower end....unless that something hits the lower end

 

[Ruggybuggy]

Re: 3-blade vs 4-blade

The holeshot is better on the four blade but the top speed is higher on the three blade.

 

[trendsetter240]

Re: 3-blade vs 4-blade

I need to get a 2nd prop for my boat.

It's a 17 ft. 4 Winns with a 1984 115 hp Johnson. I am currently running a Michigan Wheel 3-blade 13 1/4" x 17 aluminum prop and it seems to be a spot-on match for my rig.

As I've been looking over all my prop options, I was kind of considering trying a Solas 12 3/4" x 17 4-blade aluminum. What are the advantages and disadvantages of the 4-blades?? If the pitch remains the same, will top speed also remain the same with a 4-blade??

Also.......what about the Comprop's?? Are they worth it to save a few $$ ??

What is your WOT with the current prop?

I've been an aluminium prop guy for quite some time. They work great and are inexpensive. I recently purchased a 4 blade Solas HR Titan stainless but have yet to try it out.

Sure looks pretty on the back of my boat in the yard though

 

[V4 Johnson]

Re: 3-blade vs 4-blade

What is your WOT with the current prop?

I've been an aluminium prop guy for quite some time. They work great and are inexpensive. I recently purchased a 4 blade Solas HR Titan stainless but have yet to try it out.

Sure looks pretty on the back of my boat in the yard though

WOT is 5500-5550 RPM and 41 mph with just me aboard.

A stainless prop is really not an option for me, though, due to the treacherous (submerged rocks) waters the boat is run in at times.

 

[V4 Johnson]

Re: 3-blade vs 4-blade

Another question along the same lines...........

If the 4-blade will give a better holeshot but less top speed, would the same be true for a 14"x17 3-blade versus a 13 1/4"x17 3-blade??

 

[Ruggybuggy]

Re: 3-blade vs 4-blade

Another question along the same lines...........

If the 4-blade will give a better holeshot but less top speed, would the same be true for a 14"x17 3-blade versus a 13 1/4"x17 3-blade??

Generally speaking a smaller diameter will give a better hole shot, it allow a little more slip and allows the motor to get it's power band. You have to remember that there are so many other factor that can contribute just as much such as rack, cupping and shape that the only way to tell is to try them. I like to work with my local prop guy, he's says try this one and I take it out for a try and if it's not right he'll keep exchanging until we get it right.

 

[hwsiii]

Re: 3-blade vs 4-blade

V4 Johnson, if you will buy a Solas Amita in a 15" pitch your hole shot will increase dramatically, your RPM will be right and you will lose less than 2 MPH at WOT.



H

 

[V4 Johnson]

Re: 3-blade vs 4-blade

V4 Johnson, if you will buy a Solas Amita in a 15" pitch your hole shot will increase dramatically, your RPM will be right and you will lose less than 2 MPH at WOT.



H

Is the RPM gained/lost per degree of pitch different for the 4-bades?

Theoretically, if I dropped from my current 17 pitch to a 15 pitch 3-blade, I would gain 400 RPM's at WOT, right? That would put me right near 6000 RPM WOT. I think that's too high for my engine's recommended operating range.

Many thanks to everyone for the help!!

 

[skargo]

Re: 3-blade vs 4-blade

I've talked to a couple prop companies and they said the losing mph at top end is old technology, that the new designed props don't lose anything on the top end.

 

[hwsiii]

Re: 3-blade vs 4-blade

You will gain right at 200 RPM and the people who are knowledgeable on your motor recommend that it should run about 5,800 RPM with todays gas.



H

 

[V4 Johnson]

Re: 3-blade vs 4-blade

You will gain right at 200 RPM and the people who are knowledgeable on your motor recommend that it should run about 5,800 RPM with todays gas.



H

Thanks for the info!!

 

[Bayliner175xt]

Re: 3-blade vs 4-blade

Hi Try a Piranha prop, they are composite and work well.
We run one on our 3.0 Mercruiser and it has saved us a bucket of $$$$
you can change Dia and pitch in just 1 minute

http://www.piranhapropellers.com/

We have 3 sets of blades spare. still cheaper than buying 1 alloy prop

 

[NoKlu]

Re: 3-blade vs 4-blade

I have been wondering about the difference as well. I read on one site that 4 blades get the prop slip, numbers at a lower rpm. If you are getting say 10% slip with a 3 blade at 4500 rpm a 4 blade will give you the same slip but at 2000 rpm. That makes them more efficient at cruising speed which means better fuel economy. Is this correct?

 

[hwsiii]

Re: 3-blade vs 4-blade

NoKlu, the theory is right, BUT at 2,000 RPM most boats will not even be on plane, so you need to be on plane to really get the lower prop slip numbers and better cruising numbers.



H

 

[hwsiii]

Re: 3-blade vs 4-blade

V4, you are very welcome.

You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.

http://forums.iboats.com/showthread.php?t=369057



H

 

[Slojoe]

Re: 3-blade vs 4-blade

A stainless prop is really not an option for me, though, due to the treacherous (submerged rocks) waters the boat is run in at times.

If you hit a rock and lose metal off an aluminum prop, a 4-blade tends to vibrate less than a 3, so you can keep it for a backup. Also 4-blade props vibrate less to begin with, at least in the cheaper versions that I buy.