prop slip calculator

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prop slip calculator

Postby 95LSDIY » Thu Aug 23, 2012 8:09 am

Okay guys on the other thread about the wrap and speed, blewbyu had poseted a like to a prop slip calculator. Well I had sold my boat, but I remember all the numbers so I entered them in. Accoriding to my tach reading 4800 rpms, my gear ratio on my alpha one being 1.98, the prop was a 17p michigan rapture, and the gps speed was 41 mph full take of gas, normal gear including 3 batteries and 300lbs of sand in the bow and a 3.0LX merc it says I had -.02 slip and that speed was too fast even with no slip... my speed was taken with a gps app for my phone as well as a garmin nav unit that shows speed. So I'm thinking my tach wasn't accurate and I was turning more than 4800?

Any ideas?

This is with a 1995 1750br 3.0LX and alpha one.
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Postby BlewByU » Thu Aug 23, 2012 9:27 am

I have a digital Tach I compare to the stock analog Tach and there is always a difference between them. I trust the digital tach more.
2007 Caravelle Interceptor 232SS, 350 Mag, Bravo1
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Postby buyfire » Thu Aug 23, 2012 10:52 am

the more satellites a GPS unit is receiving, the more accurate it's going to be. if the unit in your phone is only locked on to 2-3 satellites, the accuracy can be way off. you'd need to be locked to about 5+ to get a really accurate reading. the fella i bought my boat from showed a 73MPH GPS reading with an accuracy of about 50 feet. with an accuracy of about 9 feet i show 67MPH.
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Postby BlewByU » Thu Aug 23, 2012 11:25 am

^^ Exactly! I see a difference between my phone GPS speed and my In dash GPS Perfect Pass speed control. The Perfect Pass is much more accurate.
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