Re: Evinrude e-tec or Yamaha 4 Stroke
Mr. Canadian,<br /><br />You must be getting a little LOST reading all these posts and getting a bit mixed up.<br /><br />I always agreed with Forktail that the one performance test did not compute using a 15" prop. I assumed that it was a misprint that traveled "up the line" somewhere. My feeling were that it was a 17" prop, which would "fit" mathmatically. I also explained refiguring the formula for theoretical speed to account for cupping on a prop which results in increase efficiency (speed) on most boats. It is a formula that has been widely used for over 30 years by manufacturer's and technicians. Of course it is a "rule of thumb" and is only a guide for quick calculations to account for the speed differences in cupped and un-cupped props on a variety of boats. <br />On the water testing with accurate instrumentation is the only "true" way of determining performance.<br /><br />Some of the posters here are well experienced in the recreational boat industry and have freely shared accurate information. It is one thing to read books, articles, and newsgroup postings, then expound on the literal interpretation of something, making yourself sound like an "expert", whether you are a retired engiineer or not - but it is something else to be knowledgable in your profession and experienced enough to see the whole picture, not just a paragraph in print.<br /><br />I know a few of the more technically experienced members of this forum, and you would be very suprised on their depth of experience, their accomplishments, and their job titles in this industry.<br /><br />This post is not to criticize or bad mouth anyone, just to explain that you have to "see the forest thru the trees" and how to cut thru the dis- and mis-information that is posted by some folks, whether deliberate or not.
Mr. Canadian,<br /><br />You must be getting a little LOST reading all these posts and getting a bit mixed up.<br /><br />I always agreed with Forktail that the one performance test did not compute using a 15" prop. I assumed that it was a misprint that traveled "up the line" somewhere. My feeling were that it was a 17" prop, which would "fit" mathmatically. I also explained refiguring the formula for theoretical speed to account for cupping on a prop which results in increase efficiency (speed) on most boats. It is a formula that has been widely used for over 30 years by manufacturer's and technicians. Of course it is a "rule of thumb" and is only a guide for quick calculations to account for the speed differences in cupped and un-cupped props on a variety of boats. <br />On the water testing with accurate instrumentation is the only "true" way of determining performance.<br /><br />Some of the posters here are well experienced in the recreational boat industry and have freely shared accurate information. It is one thing to read books, articles, and newsgroup postings, then expound on the literal interpretation of something, making yourself sound like an "expert", whether you are a retired engiineer or not - but it is something else to be knowledgable in your profession and experienced enough to see the whole picture, not just a paragraph in print.<br /><br />I know a few of the more technically experienced members of this forum, and you would be very suprised on their depth of experience, their accomplishments, and their job titles in this industry.<br /><br />This post is not to criticize or bad mouth anyone, just to explain that you have to "see the forest thru the trees" and how to cut thru the dis- and mis-information that is posted by some folks, whether deliberate or not.