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Low RPM's

2K views 7 replies 4 participants last post by  MobjackB32 
#1 ·
I have an Universal M3 20B with about 450hrs. She runs like a top but, after being put in service this spring she will only run up to 2100 rpms. This is under load or in neutral...doesn't make a difference. There is no lag or stutter, runs fine and pushes along at hull speed
What could be the causitive factors of such an issue and is it possible that the tach is not reading correctly (although it does register the proper idle speed) thanks!
 
#8 ·
I have a universal 5424 and have the same issue. After much angst, I ordered a laser tach off ebay for about $10. Using the laser tach I determined that my boat tach was way off and I feel much better. I also believe that the prop is over pitched and will be having that adjusted this winter gaining an extra 400 rpms. One of the ways to tell if it is your prop is to see how fast you move while idling.

If you are moving at hull speed at 2100 and the engine feels normal then it is probably your tach. Does the engine sound the same? You should notice a big difference in sound if she used to run at 3600 and now only runs at 2100. Your ears will tell you if you are that far off. Vibration will too.
 
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