# Prop slip



## WALI4VR (Jun 4, 2017)

What would a decent percentage of prop slip be? I'm coming up with 26% for my rig which seems awful to me! 
14"pitch x 6000rpm =84,000
1056constant x 1.83 lu ratio=1932.48
84,000÷1932.48=43.5 mph (Theo) 
43.5-32 actual mph=11.5
11.5 ÷43.5=26% slippage an...YIKES

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## KMixson (Jun 4, 2017)

You have to figure the prop pitch is measured in a perfect world. You will never get that. 32 MPH sounds good to me.


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## DaleH (Jun 4, 2017)

I'd run your rig info through the prop calculator posted as a sticky post on the motors forum.

What hp motor? Boat make/length/design/style?


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## Stumpalump (Jun 4, 2017)

7-20% Are you sure it's 1.83 gears? If I put in 2.32 it puts it at 7%. Is it really a 14" prop? What kind of tach and is it set for your motor? Is it a two blade prop? They slip more. Light boats slip less. Pontoons slip a lot. Use this next time: https://www.mercuryracing.com/prop-slip-calculator/ and check slip at cruise RPM. It's easy to ventilate, over rev and slip when your trimming it out and raising it to wring it's neck out but it sure is fun!


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## WALI4VR (Jun 4, 2017)

1999 mercury 4cycle 50hp carbureted on a Lund Explorer 16 ft aluminum tiller. Prop is 3 blade 10 3/8 diameter by 14"pitch which is OEM. WOT is 5990 rpm all day long and lu is 1.83.its NOT A BIG Foot with 2 series gearing. 

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## WALI4VR (Jun 4, 2017)

Just tried Merc calculations 26%,i rounded up they rounded down

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## squid013 (Jun 5, 2017)

It depends on the prop being used and the drag of the hull, and if the prop is cavitating which I suspect it would be. But yes you did your numbers correct. And you can even estimate what slip to expect by knowing your wind and current

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