Rev-Range

Rev-Range

Every maker of marine engines specifies a recommended full-throttle rpm for each model it produces. This information is somewhat like the “redline” rpm that automotive manufacturers specify, but in the marine case, it carries far more ramifications than a simple “redline” that one must stay under. Unlike automobiles that have multiple forward gears, marine transmissions have only a single forward speed. In a terrestrial vehicle, if your rpm is too low or too high, the driver can change gears so that the engine is not over loaded or over-revved. In a boat, the only way to alter the load being put on the motor is to change the propeller size. To help you determine when the propeller you are using is either over-loading your engine or allowing it to over-rev, the maker specifies the allowable full throttle rpm as a range.