Quote:
Originally Posted by Maine Sail
Most all engine manufacturers suggest the engine be able to hit max rated throttle with a clean prop and bottom.
You're not "backing off" 20% from max RPM you are forcing and over loading your engine and thus preventing your engine from hitting max RPM by over propping it.
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From one of my Perkins manuals it states that the max rating of 4000 rpm should not be run for longer than 45 minutes of every hour with the rpm reduced by 20% during the 15 minutes before returning to max rating. However it goes on to state that if the wide open throttle setting is less than the max rating then it too should be backed off by 20% every 15 minutes on the hour. In other words the WOT setting should be treated as the max rating.
I've always heard the term "over proped" and understand that to get the hp rating of the engine that certain rpms should be obtained. However I do not understand if I'm operating the engine at a lesser rpm that I'm over loading it even when I'm not able to achieve the desired rpm rating. Is there some physical sign(temp rise, smoke from exhaust, strange sounds) to show that the engine is being overloaded??