Thunderstruck

The leading edge cones are pointy.

Outdrive1

I only noticed a slight speed increase when I added Hydromotive nose cones to my vee bottom but I did run at the speed at a lower rpm, with less slip. The boat also handled completely different, more midrange punch and it felt like it was more stable at speed. The only down fall I noticed is that sideways rollers that wouldn't have much of an effect on the boat before really pulled the boat hard into them after. It actually scared the crap out of me the first time it dipped way into one running 80. I thought I was going to roll the boat. It litterally had that much more grab to it.

Outdrive1

Imco's design is said to be one of the fastest.

kylemenz1

This may be a silly question but I'm new to outdrives. What is slip and how do you measure the %?

4mulafastech

Slip is simply the difference in percentage comparing actual speed and theoretical speed. Theoretical speed is when you take into account engine rpm, gear ratio and prop pitch and calculate the 'theoretical' speed. If your actual speed = theoretical speed you have 0% slip and you should throw a party! ...never happens, typical is 10-15%, or in other words, actual is 10-15% lower than theoretical.

Now you can get your pen, paper and a trusty calculator or just go here and play around. Make sure your 'actual' speed is gps or radar verified!

http://www.go-fast.com/Prop_Slip_Calculator.htm

Tinkerer

Tibbs - I put IMCO 2 inch shorties on my SCARAB.
You are right - as they come from IMCO they are not very pointy.
I did a LOT of work to mine to get the leading edges a little sharper.
Dont go to a point on the point of the nose or it won't stay sharp the first time you hit a twig in the water.
There is a reason they have a SS point on the SSM drives.

Rebel_Heart

I was looking at adding a nose cone. But added -2" Imcos. One of the best decisions I've made on my project.

Tibbstoy2

Thanks for the input guys!

So I'm assuming that a total knife edge will be a waste of time. I'll start as it is and then add a little shape to it afterward to get a before and after...

It's all about getting the slip down... I don't care a lot about top speed, but 18-20% slip when I know I can get around 10% with this boat tells me I need to look at props and lowers.

kylemenz1

Great answer! Thanks.

Thunderstruck

The formula is:
Slip = (1-actual speed/theoretical speed) x 100%

Theoretical Speed = rpm x pitch/1056/gear ratio

Get good rpm and speed measurements and be honest with yourself!!