SLip question

[quackaddict1]

What is considered a normal amount of slippage for aluminum and stainless props?

 

[Texasmark]

Re: SLip question

I think 12% is a good number for SS. Aluminum is probably higher as people say the blades bend back......course I never was in the water holding onto the prop to verify that....grin....sorry a little humor. But slip is a rubber number as there are soooooo many variables that can affect it. Only way to really know is to test it on your rig under your operating environment.....everything else is just wild speculation. You can calculate engine rpm's, lower unit gear ratio, blade pitch and come up with a number in mph. Then compare that to your actual (GPS) velocity and any difference is either prop hub slippage, or water slip.

HTH

Mark

 

[steelespike]

Re: SLip question

Figuring slip numbers depends on accurate input. Gear ratio needs to be confirmed rpm accurate,and hull configuration is a real sticking point. Heavy boats and those like pontoons will have high slip numbers.Small motor on a boat its not intended to push will have higher slip[ numbers.

 

[quackaddict1]

Re: SLip question

I figured I was shooting for a rubber number, according to my calculations (with accurate tach and speed) im at about 15% slip with the current aluminum prop. I was running some numbers on what a different prop with better bite would give me in the same pitch. To pick up any speed even 1 mph I would need to get a prop that would get me into the 7-10% range, which I think is attainable.

Steelspike, the boat has a 60 hp with a 75hp max, given the huge weight disadvantage the 75 has, I think the boat is in good shape with the 60.