Prop Cup

[Flhx]

I have a 2005 Mercury 4 stroke bigfoot with a 14X11 prop. I would like more RPMs out of the motor, presently it is 5400. I am going to put on a Black Diamond 14X10 cupped prop. Can anyone tell me what I can expect in RPM change?

Thanks

 

[etracer68]

Re: Prop Cup

Generally a cupped prop adds 1 or 2 to the pitch.

 

[Robbabob]

Re: Prop Cup

Meaning, your RPM is likely to drop by some 300-400.. not the direction you want it to go.

 

[John_S]

Re: Prop Cup

I agree with the statements above and have experienced that with Hustler props. I wouldn't consider a stock black max as cupped, unless it has been modified by a prop shop.

Can you provide your current wot rpms, speed (gps prefered), engine hp, gear ratio, and recommeded wot rpm range?

 

[Flhx]

Re: Prop Cup

Decided to go with a 14X9 uncupped. Would like to get to 5800 RPM's, right now I am at 5400, with a 14X11.

 

[John_S]

Re: Prop Cup

Decided to go with a 14X9 uncupped. Would like to get to 5800 RPM's, right now I am at 5400, with a 14X11.

Is this a heavy boat, non-planning (like pontoon), or have allot of deadrise? A 14" dia prop would tend to be on the large size for a typical outboard, which is more like 13".

 

[Flhx]

Re: Prop Cup

21 ft pontoon ,60 hp bigfoot, somewhere around 3200 lb.