Do I need to sharpen and balance my new prop?
The question of whether props need to be sharpened and balanced, and how it should be done comes up often. The answer to the first question, should they be balanced, is absolutely yes! Prop manufacturers sell unbalanced, dull props. In theory, they could balance and sharpen them before they sell them, but since boaters tend to "personalize" their props it's probably best that the manufacturers sell raw props. Shipping them raw also makes them less succeptable to damage during shipping and handling in stores.
So, what does a new person do with this raw prop? Well, there are several choices. The first is learn to sharpen and balance props. I provided links below to help those who might want to do this. Another option is perhaps you have someone local who can sharpen it for you. And the final option is many of the racing oriented online vendors offer a sharpening service. For a small fee, they will take that raw prop you order from them and send it to you sharpened, balanced, and polished and ready to put on your speedy new boat. If you're not excited about spending a couple hours with the prop, a few files, an assortment of really fine sandpaper, and a prop balancer, I heartily recommend letting someone else do it for you. If you're too proud to do this, consider the fact that many racers also use this kind of service.
I was going to extract information from a bunch of places and perhaps write an article on sharpening and balancing props. But if someone else has already done this, and better than I would have done, I'm just going to link to their information.
How do I sharpen and balance my new prop?
Here are some articles that describe prop sharpening, balancing, and modifications:
http://www.offshoreelectrics.com/prop_balance.htm
http://www.rcprops.com/TechNotes/rcprop_tech_info.htm
http://www.geocities.com/jwohlt5362/Propguide1.html
http://rcboat.com/prop.htm
Note, many props are made of an alloy containing beryllium. Dust containing beryllium is hazardous. Here is a link to a fact sheet:
http://www.state.nj.us/health/eoh/rtkweb/0222.pdf When working with this material, it's important to wear a dust mask, and take steps to control the dust. I prefer hand tools, rather than a dremel, because it reduces the amount of dust generated, and the distance it spreads.
What about after run oil?
Working on this section. Until it's done, here's some links to get more information:
http://rcboat.com/after.htm
How can I find other boaters in my area?
As I was writing a reply about an upcoming race I realized many people reading this thread may be interested in finding other people to run boats with, and perhaps race. Here's links to 2 North American based boating organizations:
North American Model Boating Association (NAMBA)
http://www.namba.com
International Model Power Boat Association (IMPBA)
http://www.impba.net
How do you choose which one to join? Go to the web sites, find your district and look for the nearest club. Each of the organizations has strong and weak areas, pick the one that works for the place you live.
How do I choose the right size prop for my boat?
Here are some charts showing ranges for common boat sizes:
http://www.funrcboats.com/prop_chart1.htm
Octura prop chart that Ron posted:
http://www.pirespreto.com/octura_catalog3.htm
How much oil should I add to bring my fuel up to nn%?
To determine the quantity, do the following math...
Ounces of fuel times desired percentage = desired ounces of oil
Ounces of fuel times actual percentage = actual ounces of oil
Desired ounces of oil minus actual ounces of oil = needed ounces of oil .
Note that this will be a bit off because you have to pour off a bit of fuel to make room for the oil you add. This means you'll end up starting out with a lower amount of oil and fuel, throwing the calculation off a bit. However, rather than worrying about it, the above will give you a slightly higher than the desired oil percentage , which certainly won't hurt the engine...
Here's an example:
128 ounces times 18% = 23.04 desired ounces of oil
128 ounces times 12% = 15.36 actual ounces of oil
23.04 - 15.36 = 7.68 needed ounces of oil .