Replacing Prop - 3-blade or 4?

[jmb23802]

Picked up a 2003 Four Winns Freedom 170 late summer this year. With the original VP 4.3 GL and three-blade 23p prop on this #2k boat it will get up and run nicely, gets up on plane quickly and has a nice cruising speed at 3k RPM (~30 mph); however, a little more low-end grunt may be nice in another 1-2 years when the kids get big enough for some towing sports; plus, a more robust feel when turning would be nice but not really a big deal at the moment.

The boat lived in a shallow lake prior to me and the aluminum prop (I'm guessing it's the original prop) has taken a few hits, been repaired at least once, and then dinged up again so I am going to start fresh with a new prop in the Spring but I am at a draw as to whether to replace it with a 3-blade or change up to a 4-blade. Due to cost, I will most likely stick with aluminum either way.

If I am mostly happy with the three-blade prop should I stick with it or is an upgrade to a four-blade prop worth it? If I go four-blade I am thinking about the Solas Amita-4 but if I stay three-blade will probably go with a gently used Volvo prop in the same size and pitch as the original so cost will be about the same either way.

Uses for the boat will be primarily cruising from one swim hole to the next and evening boat rides on large Corps lakes in TN for the next 1-2 years and then we will look at adding a tube and maybe an occasional adult on a water ski.

Question is: three-blade or four-blade and why?

 

[alldodge]

Picked up a 2003 Four Winns Freedom 170 late summer this year. With the original VP 4.3 GL and three-blade 23p prop on this #2k boat it will get up and run nicely, gets up on plane quickly and has a nice cruising speed at 3k RPM (~30 mph); however, a little more low-end grunt may be nice in another 1-2 years when the kids get big enough for some towing sports; plus, a more robust feel when turning would be nice but not really a big deal at the moment.

The boat lived in a shallow lake prior to me and the aluminum prop (I'm guessing it's the original prop) has taken a few hits, been repaired at least once, and then dinged up again so I am going to start fresh with a new prop in the Spring but I am at a draw as to whether to replace it with a 3-blade or change up to a 4-blade. Due to cost, I will most likely stick with aluminum either way.

If I am mostly happy with the three-blade prop should I stick with it or is an upgrade to a four-blade prop worth it? If I go four-blade I am thinking about the Solas Amita-4 but if I stay three-blade will probably go with a gently used Volvo prop in the same size and pitch as the original so cost will be about the same either way.

Uses for the boat will be primarily cruising from one swim hole to the next and evening boat rides on large Corps lakes in TN for the next 1-2 years and then we will look at adding a tube and maybe an occasional adult on a water ski.

Question is: three-blade or four-blade and why?

IMO every blade on a prop creates drag. A one bladed prop is more efficient (one blade cannot be balanced) then a 2, a 3 , and so on. Most props are 3 bladed due to balancing the prop and least drag. Your boat is handling fine but could use some more low end torque (grunt) when pulling loads in the future. A 4-blade prop will give you more lift at the stern which is bad for low speed pulling. I would suggest fix or replace your current prop with the same for overall performance. Get another 22 or a 21 at the lowest for more hole shot. When using the lower pitch props you will come out of the hole quicker but you can over rev if not pulling and going for WOT.

I run a 21 on my Rinker and also have a 19 for when I want to do some heavy pulling and it works out very well

 

[steelespike]

A 3 blade usually provides good all around performance.A 4 blade usually provides better holeshot,should stay on plane easier at reduced throttle,
May seem smoother and should respond better around the dock.
Usually suggested to reduce pitch 1" to help maintain rpm and you may lose a little top end.
The Solas props have a good reputation. The Solas Amita has a permanent hub the Rubex is the same prop with a removable hub.
You should get your prop repaired and get us a lightly loaded wot rpm and gps speed.
It will tell us if your setup works and hopefully what changes are needed if any.
You can keep the repaired prop for a spare or sell it on Craigs list.

 

[Mi duckdown]

jmb pics of Dinged up prop. every ones idea is different of dinged up

 

[jmb23802]

I am a little confused AllDodge...you say stern lift is bad for low speed pulling but wouldn't it be better to get more stern lift so I can plane off at lower speeds instead of plowing around when towing a tube?

As requested, I am trying to attach some links to pics of my prop - the prop is far from pristine but overall maybe not too bad. Not sure if this is a good candidate for repair and back-up service or if this prop can be a very good performer with a little repair.

 

[Starcraft5834]

Ive got a 4 blade Solas Amita....if your boats heavy.. 4 blades is best overall option... and IMHO provides best overall performance

 

[steelespike]

Referring to 2,3 and 4 blade props 2 blades are considered best for top speed not particularly good for heavy weight or hole shot.
The 3 blade is better for overall performance with a little less top end and then the 4 blade with its low to mid range performance.
These are very general classifications and there may be some exceptions ie: the Merc. spitfire.
Then there is the high 5 with its amazing nitch performance.

 

[scutty]

I recently went through the process of upgrading my prop. I went to a SS 4 blade from a 3B AL and it was the best money I've spent on a boat. Way better low and mid range performance and not much lost off the top end. Because there are soooo many factors that go into matching a prop to a boat to a driver I strongly recommend working with a prop shop that has an exchange program and will let you swap props until you find the set up that works for you. I had to try three different geometries before I found the one that worked for me. There are lots of different prop designs out there. There are 4 blades that are designed for stern lifting while others are designed for bow lifting. See Merc Rev4 vs Trophy. Some work better for outdrives and other are designed for sterndrives. Some are designed for speed and others for rough water handling. If you can give some more of the data ( read the sticky notes at the top of the forum ) i.e. WOT, GPS speed etc folks can give you some more specific suggestions. Hope this helps-

 

[Lager]

I went from a 3 blade alum 19 inch on my 18 ft 3.0 liter bowrider to a 17 inch Solas 4 blade that I bought here. I noticed a big difference in hole shot to plane, smoother or less vibration and much better prop hold in tight corners at speed.
But I lost about 6 mph in top speed and about 5 mph at 3k rpm or cruise speed. I think what O should have done was only drop one inch of pitch for the 4 blade and I would have a better package. I use the 4 blade when Im pulling the kids and the three blade when Im going out to cruise the lake for better fuel economy.

 

[blackhawk180]

I recently went through the process of upgrading my prop. I went to a SS 4 blade from a 3B AL and it was the best money I've spent on a boat. Way better low and mid range performance and not much lost off the top end. Because there are soooo many factors that go into matching a prop to a boat to a driver I strongly recommend working with a prop shop that has an exchange program and will let you swap props until you find the set up that works for you. I had to try three different geometries before I found the one that worked for me.-

My experience and results exactly.

 

[jmb23802]

Since my boat is now winterized for what is supposed to be a long and cold Midwestern winter, I will get my current prop fixed/replaced for now. Next season I will get a real-world performance baseline for the boat "as-currently-propped" and then decide what adjustments to make from there. Since my engine compression numbers are less than amazing (low side of good compression range) I may just find that I need to take a couple steps down in pitch to compensate and get the engine running in the optimal RPM range again and that may be all I need until we start towing stuff. Again, it sounds like a lake test at WOT will tell a big piece of the story.

I like the idea of finding a shop that will work with you and let you exchange props. I'll have to see if anyone in my area will do this.

Thanks everyone for the advice! If I end up changing props I will post back next season.

 

[jmb23802]

It has been a long time but figured I would close this one out for posterity. Here is a quick summary of my own meandering prop replacement efforts and results:

Bought our boat with the original aluminum 14.25 x 23" Volvo prop that had been beaten and repaired more than once. Prop was messed up so I didn't bother running at top speed to get a reading. Boat documentation said top speed should be in the neighborhood of 50+ mph.

Bought a Viper 3-blade stainless 14.75 x 21" that was a fast prop once on plane and WOT rpms were perfect, but the bow would point at the moon when we took off so we kept looking. On plane, you could feel even minor throttle movements in your seat as it was very responsive, which we liked. Top speed was about 46-48 with our usual load.

Bought a 14.? x 21 stainless Volvo Penta 3-blade prop but throttle response was vague and mushy and just 'meh' compared to the Viper acceleration. Sold it after one boat ride. Bow rise was almost as bad as the Viper.

Decided to move to 4-blade prop to get more stern lift in hopes of keeping the bow more level on launch. Bought a 14.X x 21 four blade Solas prop. Prop did a great job keeping the bow down and nice crisp throttle response (response not quite as active as the Viper though) and the boat popped right up on plane, but the engine sounded strained and could only reach WOT RPM that was, at best, the minimum recommended RPM for the boat. Top speed was in the low 40's

Bought a 14.25 x 19 4-blade Solas stainless prop and we are finally happy. Boat launches out of the hole and presses you back in your seat when it starts to plane off. Bow rise is minimal. WOT rpm is at the max of the recommended range when we are loaded normally. Solid and steady power delivery through turns. Top speed is around 44 mph. So we lost around 2-4 mph over the Viper and about 6 mph under the factory but some of that could be the way we are loaded.

Took four props to replace the aluminum with a stainless but it was worth the effort. Love the way the boat handles now. For reference, our typical load is 650 lbs of passengers and call it a 150 lbs of gear (tools, two anchors, canvas covers, skis, tube, coolers, towels, life jackets, and so on).

 

[SeaDooSam]

Sounds like you figured it out well! Exactly what we did. Trial and error is by far the best way even if it isn't the most economical!

 

[HT32BSX115]

IMO every blade on a prop creates drag. A one bladed prop is more efficient (one blade cannot be balanced)

Hmm..... This one is balanced!

(now don't get me wrong........I'm not suggesting anyone try a 1 bladed prop on a boat. But it would work. And it could be balanced.....just like the one above. But I am not suggesting it would be better than the current choices!!

For the OP,

Glad you got the right prop on the back!

More blades will pretty much always give you better hole shot and slightly lower top speed (due to the additional drag) but the trade off is usually worth it!! I went from 3 blades to 6 (3x3 contra-rotating) blades with essentially the same HP! The (hole-shot) difference was spectacular and the loss of top speed was largely negligible.

Cheers,


Rick

 

[SeaDooSam]

Hmm..... This one is balanced!

(now don't get me wrong........I'm not suggesting anyone try a 1 bladed prop on a boat. But it would work. And it could be balanced.....just like the one above. But I am not suggesting it would be better than the current choices!!

For the OP,

Glad you got the right prop on the back!

More blades will pretty much always give you better hole shot and slightly lower top speed (due to the additional drag) but the trade off is usually worth it!! I went from 3 blades to 6 (3x3 contra-rotating) blades with essentially the same HP! The (hole-shot) difference was spectacular and the loss of top speed was largely negligible.

Cheers,


Rick

Correct me if I'm wrong but that looks like a two blade to me

 

[HT32BSX115]

Correct me if I'm wrong but that looks like a two blade to me

Nope, just one. The other "side" is a counter weight

Here's a better picture!

 

[SeaDooSam]

Nope, just one. The other "side" is a counter weight

Here's a better picture!

Oh I see! That's a better picture. Cool!

 

[H20Rat]

A 4-blade prop will give you more lift at the stern which is bad for low speed pulling.l

You WANT stern lift for low speed pulling! Best thing I did for towing young kids around on a tube was to get a 4 blade prop. I can now stay on plane around 15-16 mph, with a 3 blade I was at 20 mph and even then just barely.

 

[HT32BSX115]

You WANT stern lift for low speed pulling! Best thing I did for towing young kids around on a tube was to get a 4 blade prop. I can now stay on plane around 15-16 mph, with a 3 blade I was at 20 mph and even then just barely.

You can also easily control stern-lift with drive trim and trim-tabs. I can completely control it with my Bravo III + Bennett tabs....