MnFastBoat
Dont get in a big hurry, I talked to Mercury Racing Friday and was told that their Labbed five blade props will be out in the latter part of Jan. they gave me the part numbers so that I can get either a 30, 32 or 34.
It might be worth the wait after all where can we go with this snow and ice?

I recently saw a 36 daytona with 5 blades - they looked like Hydro's. My guess is that he was blowing out rolling on plane. Most will tell you that the fewer blades the faster top end. Next, you keep rasing the drive until you loose speed or blow out getting on plane. I would think that the 5 blades will be helpfull on extremely high drive heights were the gain from a lower coefficient of drag outweighs the loss of efficiency with an extra blade in the water. I did some testing on my daytona and with a direct replacement to a Blackhawk, I gained 10 mph, which has 6 blades. Once again, the gain is having a drive that is 5.5" higher out of the water, not the extra blades.

john.sblendorio,

Great analysis. The assumption some make, that fewer blades are faster then more is WRONG! As you stated it's all about setup regarding the prop selection. Sometimes a 5 blade is fastest, sometimes 6, sometimes 2,3 or 4. It all depends on the setup of the boat and what the customer wants from the prop setup.

On a setup for acceleration and top end speed you should expect the prop to "blow-out" while getting on plane.

With a boat set up to run a 6 blade prop I would expect it to have a higher X dimension then it would with a 5 blade prop. Of course there are advantages with 4, 5, and 6 blade props that can't be seen on paper. Some boats just like certain props and sometimes the driver of the boat likes the feel of a certain prop and thats very important.

There are times when I see a boat pick up speed with more blades while nothing else was changed. It's nice if you can try different props before you buy a set so you have a good idea of what to expect when you deceide on the prop you want.

There is a lot of new technology in props out there right now. 5 and 6 blade props that didn't exist just two years ago. It's exciting that there is a great selection of high performance props on the market that will fit any application.

Matt

Think that you are right on the money when you are talking the right set up for each different boat. Mercury has been making props for my cat and they indicated that by using their new lab 5 blade I will drop from 16 per cent slippage to 10 0r 11. At present Im using 130 ratio with 34 Labs,2' in shorties and turing 6100.Thats a pretty big pickup for me. Will keep you informed as how much good they really do me..But dont mind telling you that you are right when I carry extra people I have a harder time rolling it over. hope new props can cure that.Only time will tell.

Les, Can I slip a quick Happy Birthday in here for you?

To you prop experts...... Does a reduction in prop slip automatically lead to an increase in speed?

I am looking forward to testing the new Merc 5 blades. We will have a set of 30's next week. Just need to find a boat that can turn them and see what they do.

We were told it would be late Jan before we see the 32's or 34's. We will just wait till they arrive. Since it's a new prop it will take a little working to find out what it likes and dislikes as far as improving performance.

I was able to check out a set at Lake X a couple months ago. There is a lot of blade area there!

Matt

Boatfreak28
Thank you for the Birthday wishes We at our home wish you and your family a Merry Xmas and a great New Year!!.

Matt, Thanks for the kind words you must be both a gentleman and a scholar. How about you send a RH 30 my way to test?

On my boat, I have run stock and xr geared bravo1 drive in a 1.5, 1.36 ratio, stock height w/ no nose cone, +2, +3 IMCO's with nose cones and 12" extension box, lab 28, lab 30, stock 32 bravo 1 4 blades, Hydromotive 4 blade, mach 4 blade and a three blade Mirage plus on a bravo 1 drives. With a backhawk, I have run stock 1.5, 1.36 ratio on stock gears and xr gears, stock height w/ 29" props, lab 29, lab 31" props, custom made lab 33's, +3 / 12" extension box with the same schenario. I would be happy to let you know the outcome. If it works you may even have a sale or two, as a 25 daytona is a fairly common hull design on this forum.

Mike,

I don't think you can say reduced prop slip automatically means better speed. Slip is a tool. We don't get too caught up with the prop slip numbers. If a prop with a higher slip runs better than thats the one to go with.

The other problem with prop slip, which I see frequently is the pitch number. Most of the time the improper pitch is put into the formula therefore the incorrect slip is computed.

For example; A 32p lab finished 3 blade cleaver is actually about 30-30.5" of pitch. A 32 pitch Hydromotive 4 blade is 32-32.5" of pitch. If you use a pitch of 32 to calculate the slip, for both props, you can see how the Hydromotive prop would calculate a lower slip number.

When you lab finish a prop, or anytime the cup is adjusted, the pitch of the prop is again changed so an accurate measurement of the prop would be necessary to come up with an acurate slip number. Putting a pitch gauge on the prop is not an acurate measurement of the pitch of the entire prop. Since the pitch, on many props, changes at various points along the blade it's impractical to use a pitch gauge.

Point of the story, don't get too wrapped up in slip numbers, use them as a tool.

Matt