Hello,<br /><br />I have some questions calculating engine speed of a rib with two engines:<br /><br />1.) E-Tec-50hp: i=2,67, prop=3 x 14 x 17<br />measured max speed = 59.9km/h / 6000 rpm<br /><br />2.)Honda 50hp: i=2,09, prop=3 x 11.5 x 14.25<br />measured max speed = 59.4 km/h / 6000 rpm<br /><br />I must calculate the E-tec with a far less slippage of only 4 % due to the 14 " diameter and an additional 1 '' of pitch due to cupping to calculate 6000, the measured value.<br /><br />The Honda on the other hand needs a more common slippage of 8 % and a less pitch increase of 0.5 '' due to cupping to meet the measured 6000.<br /><br />Do you think that all is realistic.<br /><br />I know increasing prop diameter decreases slippage, but will it make 4 % ?<br /><br />And are the assumptions for speed decrease due to prop cupping realistic ?<br /><br />They are derived from:<br /><br /> http://www.mercurymarine.com/chapter_4_-_propeller_technology <br /><br />Greetings from Germany<br /><br />Nordy
