Ok, I am actually posting for a friend of mine who is looking to get a better propeller for his boat but doesn't know where to begin. I will provide you with the information that I have and get answers to more questions if need be. The boat is a 2002 21' Glastron, boat construction is fiberglass and it has a V Hull. It is equipped with a volvo i/o that is powered by a chevy 305. At WOT the rpm's are about 6000. He is looking to get maximum performance as a wakeboard/ski boat and wants to get a new prop. Right now all he has is the stock prop and is trying to find more information about it for me. No tabs, foils, or jackplate to his knowledge, he did mention a 'whale tail' but I don't know what that is. Thank you for your help, we are also located in Colorado so if Altitude is a factor we are at about 6000 ft.<br /><br />Seth
<br /><br />Altitude is definately significant. The motor can't produce as much power as at sea level due to the thinner air. There is a high-altitude gearset fot the outdrive. If the motor has a carburetor, i'll need different jets.<br /><br />First thing we have to do is find out how many RPMs he's Really turning. I'm betting that the tach is set for a 6 cylinder. There's no way that motor will turn 6 grand. If it is set for a 6, he's turning 4500 which is way more realistic and pretty much on target.<br /><br />Whale tails can help with quicker planing, but can adversely affect handling, and they slow you down. Trim tabs are much more effective without the negative side effects.<br /><br />There are certain props that produce Stern lift such as Mirage stainless and Alpha 4-blade aluminum models. High-Five props also work nicely when power is a bit low for the application. Regular 3-blade aluminums are fine, but made to fit anything. The first two props I mentioned are specifically for sterndrives.<br /><br />See a dealer in your area. Chances are they know all about high altitude modifications. If it was purchased up there, I'd hope those were already addresssed by the selling dealer.