Prop Experts Please Take a look

[KNOT-RIGHT]

Shown below is a 17.5x32 Mercury 5 blade and A Rolla 17.5 32 blade.

Notice the tips of the rolla is looking more like Chopper Round ear
Compared to the mercury which resembles a Cleaver style.
These are both surface piercing. Can You explain the differences
of these props.

Would one give more stern lift, or bow lift??


The Application: Arnesons on a V bottom
Positive trim is difficult to obtain.

Thank you in Advance for your Explanations

Gerry

[HOUSTONPROP]

The Merc has a much larger blade surface area,This will give you much better crusing capabilities ,holding the boat on plane much easier also with the pointed tips ,This will allow you to pierce the surface using the tip of the blades which will result in greater speeds on top end ,also it should lift the entire boat up and out of the water reducing the drag ,The rolla prop has a much smaller blade area as you can see ,I personally think the merc will out perform the rolla night and day!Alot of this is that the manufacture may have a paten on the prop so it can not be copied .So they have to change it some to get by these laws.Hope this helps ,try them and see which one works best on your application.These are more of a stern lifting prop due to the thick trailing edge.

Darin

[KNOT-RIGHT]

Thats the opposite as I was thinking. I have the mercs here.The rollas are
copied off another post. So I cannot try them However in running the Mercs
It feels real loose in the stern Compared to my 32 4 blades. I agree Midrange is higher and the boat will stay on plain at 2000 rpm. But I think the 5 blades
are actually giving to much Stern lift. What Im thinking is there a prop
that will aid in lifting the bow with this type of propulsion system.


12 inch notch transom. no steps ,Props spinning inward.

[throttleup]

Caveman,

I would have to disagree with Darin. There are reasons why those props are designed the way they are and it has nothing to do with legal issues regarding blade design.

Give us a call and I can explain to you what can be done to your props and why the difference in blade designs will affect your boat. We work on a lot of speedmaster props for many race teams as well as poker run and private clients boats.

Matt

[44MTI]

You might want to try a set of Herrings they tend to give alot more bow lift than the mercs. You can also try a High rake Herring they are designed specifically for additional bow lift. They are quite expensive however worth ever cent. I wouldn't run my boat with out them. they make a cast version which i think retails for $5000 each, and you may be able to get a discount from some dealers.

[KNOT-RIGHT]

Originally Posted by 42MTI

You might want to try a set of Herrings they tend to give alot more bow lift than the mercs. You can also try a High rake Herring they are designed specifically for additional bow lift. They are quite expensive however worth ever cent. I wouldn't run my boat with out them. they make a cast version which i think retails for $5000 each, and you may be able to get a discount from some dealers.

I have spoke with Jim Herring regarding this. He told me to get it dialied in closer with the mercs. Then give him a call. I hear there is quite a lead time.
42MTI Can you post a picture of you herrings????

Thanks
Gerry