buttonhead40

I'm looking at prop selections and would like to hear what differences will I see in a 5 blade vs. 6 blade hering prop vs. mercury cnc prop, thanks

throttleup

We need more info on the boat to answer this question for you. We need your performance data WOT RPM and WOT MPH with your current set up including gear ratio, propeller diameter, rake, blade count and pitch as well as the year of your hull.

Julie

buttonhead40

Julie, 6400rpm, 143mph, 16.5x38 5 blade cnc merc 18 rake , 40 skater, 1000hp/side, 1.35 gear

RunninHotRacing163.1

Stick with the Mercs BIG Daddy and have Brett @ Bblades tweak em in if ya need a lil more she's running good and was flying nice from the pics i got

throttleup

I have calculated 16% slip which is NOT good for a cat with a normal range of 6-8%. The good news is there is room for improvement. There is more speed in your boat ...you just need to do some dial in work to find it! We have recently dialed in a few Race Skaters and the percentage of slip with our props and the has been low. Efficient propellers equals greater top end.

Julie

Julie

WeaponX

36" not 38"

buttonhead40

Julie, yes pitch is 36, not 38, how do your new props compare to the other 2. what is your experience with the 40 skaters, we have a 5.5" x dimension with 16" ext boxes on wet sump 6's

WeaponX

It's not 5.5" around 3.5"

buttonhead40

Julie, your right slip is in the 14% range, how do you account for number of blades in your formula, a 6 blade will have less slip then a 5 blade correct? also how do you correct for merc and hering prop pitch being 2 * by the number but same actual pitch? can we expect to get to a 6-8% slip on the 40 skater, how can we get there and what speed increase will we see between say 14% and 8%, thanks Jim

throttleup

When adding a blade we usually expect the slip to decrease, but not always. There are many varibles to take into account.
All the CNC props, Merc, Hering and ours are all very close to the marked pitch. The previous generation, non CNC, of Mercury props were about 1.5" taller in pitch than marked.

If you were to run a straight edge along the bottom of the hull infront of the drive how high above the bottom are the center of your prop shafts?

What is the thickness of your Merc CNC props? It should be stamped on the prop, something like "850HP, 1200HP, etc"?

Are you shooting a rooster tail when the boat is running at top speed? Do you have to go into negative trim to attain top speed?