wierd_dragon

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hey all,

i have a K&B 3.5 and 7.5 outboard and i'm looking for props that are already balanced and sharpened. do you have any suggestsions? 2 or 3 blades? company name? site where i can get this? also, will having a 3 bladed prop reduce the small pocket of air when the engine turns quickly and there isn't water under it for a while? (cavitation)

thanks

Ron Olson

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Try http://cmdracing.com/updated/main.htm and look at the "Prop Wall" to see what they have currently in stock. It is updated daily so keep checking in to see what you want. I recently ordered 4 props from them and they are very nicely done. I have dealt with them on the phone and on the Internet, they're great people to deal with.
Props to look for; for the 3.5, Octura X-437 to X-440 or a Prather 215. For the 7.5, Octura X-447 to X450, a X646/3 or M-447. Prather 230 or 235.
If you're getting cavitation in the corners, the motor is a little too high.

wierd_dragon

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is there a significant difference between 2 baldes and 3 blades?

Ron Olson

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This question gets asked a lot. Some props you can only get in a 2 or 3 bladed version, all Ptrathers are 2 bladed. A 3 blade prop allows at least one blade in the water at all times when using a surface drive. The problem is finding the right props for your boats. I test a lot of them for each one that I own. Once I find one that works, I get a spare one of just in case something happens like hitting debris in the water. At an out-of-town race, some boaters will run one size smaller to see how the water is. Yes, you'd think that water is water but what's in the water, sand for instance can make the water different to the boat. A smaller prop is easier to get the right tune on also is your carb is a little off on its setting.

desertbuzz

so for instance if the perfect prop for me is ...let's say ...the octura 455 .... if I get the 3 blade 455 is that better than the 2 blade?

wierd_dragon

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by what was said above and what i've learned from it, i'd figure that a 3-bladed prop would be better than a 2 blade prop because with 3 blades, one blade will always be in the water and therefore keep the boat moving more smoothly (yah?)

Mr Cajun Gator

depending on what you are wanting your boat to do. for movement the best would be a singal blade prop, in which we know, that will not be very balanced lest to say. If your wanting a prop for faster take offs then the more blades the better. As to say what prop is better, 2, 3 or 4 blades, best I can answer this is that a prop with X amount of pitch will stay the same no matter how many blades, if the "X" is the same. Once your engine reaches its max RPM with 0 slip the speed will be the same.
As stated above the best thing to do is to test different props, find out just what prop your boat wants. No 2 boats will run exactly the same.