1994 Johnson/Evinrude "ER" 9.9 thru 30 outboards Service Manual, Page 122Get this manual
RPM Limiting Power Pack Some power packs have built-in RPM limiting deviceCertain models are equipped with limiting power pack to guard against possible powerhead failures caused by improper propeller selection (underpropping), excessive wear on propeller blades, improper motor installation, propeller ventilation, or unusually light boat loadingBe sure to use the correct power pack when servicing the models listed below to control the engine's operating RPM range and protect it from possible powerhead damage due to overspeedingModel
20-30 25RW
RPM Limit
6100 5700