1991 Johnson/Evinrude EI 60 thru 70 outboards Service Manual, Page 112Get this manual
RPM Limiting Power Packs Power packs designated "CDL" have built-in RPM limiting deviceCertain models are equipped with CDL power packs 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