Re: Will changing from factory aluminum prop to SS aftermarket increase rpm's
Jason,<br /> Sound's like we have the exact same problem. I have a 2005 johnson 50hp on a 173 sport Tirton boat. It's kind of a flat bottom design, So I think we basicly have the same design. Let me start from the begining. It came with the OEM aluminum 12x15 prop. First time out i was ready to trade it off. Had great hole shot, But it hit the limiter at WOT at 34mph, and could only trim, Maybe 1/8 of the way from bottom, then it vented. In turns it was impossable. So I called the dealer and finally convinced them I needed a 11 3/4x17 prop. Put it on and took it out. It was alot better. 5600rpm at 36mph (speedo). I could trim it as far as I wanted. In turns it was better but still vented some. I found the pitot tube and the deph finder transducer mounted too low. I raised both and this fixed the venting in turns. Everything worked like it should. Then, in my quest for more speed, I bought a 11 3/4 x 17 Rapture SS prop. Bad move. I took it out. when you gassed it it when to 5000rpm and stayed there up to about 15mph then started to bit a little. It ran 38mph (speedo) at 6000rpm, which was good, but the venting was bad! In turns you had to trim all the way down and it would still vent. I liked the speed but the venting wasn't worth the trade. So I ebay'd the Rapture. Then ordered a 12x17 Ballistic prop. Took it out. It ran 38mph (speedo) at 6000rpm. But the best thing was, the way it handled. Good hole shot, could turn on a dime, and NO VENTING!!!! I love it. This prop was the best purchase I have made for my boat. Most people in this forum down the ballistic, but I'm thinking about ordering another for backup, just in case they quit making them. Oh yea, By the way. I read all the great stuff on this forum about raising the motor. All I got was venting. I don't think it helps with low hp, low speed boats. It didn't mine. I hope this helps some. I spent alot of time and money and the best thing I did was buying the Ballistic prop.
