| 摘要 |
PURPOSE:To prevent erosion of a positive electrode due to cavitation bubbles by arranging the positive electrode metallic piece which is fitted to an outboard motor having a gear part with a casing and propeller horizontally supported at its backward position, on the forward position from the propeller. CONSTITUTION:An outboard motor 1 comprises a driving shaft part 2, a gear part 4 and a propeller 5 horizontally supported and situated backward from them. The gear part 4 is mainly provided with an aluminum casing 4a, and a positive electrode metallic piece 10 (made of Zn so as to have larger ionization tendency than the material of the casing 4a, Al) is fitted to be contacted with the backward outside of casing and to prevent electric erosion of the casing. As the positive electrode metallic piece 10 is situated forward from the propeller 5 and also backward on the casing 4a, it is not eroded with cavitation bubbles 16 due to the propeller 5 and not suffered abrasion due to collision with floating matters in the water. Hence, the positive electrode metallic piece has a long life. |
