Prop help

[ers906]

I have tried to follow this thread, but the physics of fluid dynamics seem to be beyond me at this point. Can anyone direct me to a thread, website or book which can allow me to understand the basics of reduction, etc. so I can build a base knowledge and start understanding the more complicated aspects of prop dynamics.

[Mikeski]

ers,

Not as complicated as you would think. The first number is the diameter of the prop in inches, the second number is how far the prop travels forward through the water in one revolution (with zero slip). In addition to these there is also cup to the blades so the trailing ends of the blades can remain loaded after the water starts to move away from the prop. There is also a relationship between motor torque, prop diameter and slip, this is where everything gets fuzzy. My debate with Mark is really around the slip aspect of the equation. His position is that the 5.0 motor has enough torque that it does not need slip to get into the fat part of the torque curve, my position is that it does need a fair amount of slip to get into the meaty part of the torque curve to push the boat out of the hole when fully loaded. That's about it. Do some internet searches, there is a ton of information on the internet. At the end of the day the best thing to do is try a couple different props until you get one you like, no amount of reading here, there or anywhere will teach you enough to make the right decision the very first time everytime. Earlier on I failed to mention that throughout the 80's I was involved with a drag race boat team. I did some hand tuning of the props we ran. I pre-tune many of the props I run on my boats, I prefer a sharp leading edge, sharpened by filing the back near the edge very carefully.

[johnboyy7]

My boat has an 844 13.5x16. Would a 644 have more hole shot? I have 2500 ballast in 04 210.

[wcherashore]

like johnboyy7, I'd like to take the opportunity to get the opinion from two who's experience is far above my own.

I have a 2000 Air with GT-40 and am looking to put in a new ballast system with somewhere between 1200-1500 lbs. I am the primary user and wakeboard, however, my family also skis occasionally behind the boat too. Should I be looking at a new prop to maintain performance with the additional ballast?

[Mikeski]

Johnboyy,

I have already diluted this thread mixing v-drive props into the mix. For the answer to your question please look here: http://planetnautique.com/vb3/showth...4-Prop-diaries...

I will answer your question over there.

wcherashore,
Depends on what you have now and how it performs. In general I would suggest a flatter pitch prop if you are going to be running more than 1k of ballast, maybe 0.5" flatter for the first 1k and another 0.5" flatter for another 500lbs. Be a little careful running bigger diameter props, as I found you can change the wake dynamics at faster skiing speeds. I also prefer the 13.5 more than the 14.5 for surfing wakes. The wake behind the 13.5 has a cleaner surfing face and lip.

[wcherashore]

I have the stock prop and the boat will probably run with 1500lbs when everything is all said and done (roughly 1200 lbs ballast + 2-3 people on average)