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what is the proper propeller for my boat?

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ben16430

New member
i have a 5.8l omc and have been using a 14.5 by 19 prop which is what the manual said, however the boat's rpm are way to high and the speed is only about 30mph instead of the 45 to 50 mph i used to get i don't remember what prop i had on it before which size should i go to do lower my rpms? according to the manual i should be cruising around 4400 rpms but im still only at 30mph at 6000rpms. any ideas?
 
How about the rest of the story, why was the prop changed? Has the drive been worked on (gear ratio changed)? Even if you go up to a 23" pitch that's only going to bring your RPM's down to by approx 800 (5200) something is not right here.
 
19P, 1.4 ratio drive, 6000 rpm = around 60 mph with typical aluminum prop efficiency(80%)

either your tach is wrong, your speedo is wrong, drive ratio is wrong, prop is slipping in the hub, or prop is marked wrong, or all chewed up
or any combination of those 6 things
 
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