Repitch

stickerhard · Sep 7, 2011

I have a 15 pitch Stelletto prop and I was wondering can a prop shop change the pitch by 1 or 2. The prob I got is it at the top of the rpm band and just seems to slip more then my factor alum.

Dhadley · Sep 7, 2011

Re: Repitch

Describe more about exactly what it's doing. Top rpm & speed with both props, trim angles and overall condition of the Stiletto. Also can we assume it's a 3 blade Advantage 1?

stickerhard · Sep 8, 2011

Re: Repitch

i have a 15 foot runabout fibergalss and a 1979 80 hp merc . I had a 17 pitch alum on it before and would run about 5,000 rpm's and now with the 3 blade stelleto it runs close to 5700 rpms.It just feels like its slipping and not catching ahold like the alum did.I dont have a gps but i have a buddy with a 18 foot trihaul with a 115 rude on it and he used to run away from me now we are about dead even. But I think i could do better if it was cupped different or one pitch higher. I didnt know if they can do that or i need to try a different prop. thanks for the help

Bondo · Sep 8, 2011

Re: Repitch

stickerhard said:
I have a 15 pitch Stelletto prop and I was wondering can a prop shop change the pitch by 1 or 2. The prob I got is it at the top of the rpm band and just seems to slip more then my factor alum.

Ayuh,... A Prop Shop can pound abit of cup into it to fix that...

V153 · Sep 8, 2011

Re: Repitch

stickerhard said:
i have a 15 foot runabout fibergalss and a 1979 80 hp merc . I had a 17 pitch alum on it before and would run about 5,000 rpm's and now with the 3 blade stelleto it runs close to 5700 rpms.It just feels like its slipping and not catching ahold like the alum did.I dont have a gps but i have a buddy with a 18 foot trihaul with a 115 rude on it and he used to run away from me now we are about dead even. But I think i could do better if it was cupped different or one pitch higher. I didnt know if they can do that or i need to try a different prop. thanks for the help

Sounds to me like it's doing just what it should. You picked up roughly a couple hundred rpm for each degree decrease in pitch and you picked up roughly a couple hundred rpm by switching to stainless. I doubt if it's 'slipping' because if I understand correctly you say it's faster? If I'm not mistaken a Stilletto has a lil cup in it already. Those #s indicate to me at least, that appears to be a great top end prop for your rig. I'd leave it alone.

To answer your question, Yes. A competent prop shop can add pitch and/or cup. But keep in mind adding either one will have an effect on your top end.

Dhadley · Sep 8, 2011

Re: Repitch

The Stiletto will have more lift than the aluminum prop. That means less hull drag which means more rpm and speed. If you're running the motor at the same X dimension (motor height) you may be able to raise the motor. That will result in less gearcase drag. 5700 is a good number for that motor but if you reduce the drag further you may gain more rpm and speed. At that point you might be able to have more bite put in the prop. They can aslo add more lift.

BTW - pitch is measured in inches (forward travel) rather than degrees. Might save some confusion when talking about props.

V153 · Sep 8, 2011

Re: Repitch

Dhadley said:
BTW - pitch is measured in inches (forward travel) rather than degrees. Might save some confusion when talking about props.

Quite right technically, I agree. But everybody I know calls it 'pitch'. Even smart people. And try as we might I doubt you or I'll ever change that.

Pitch just rolls off the tongue easier than 'inches of forward travel"?

Dhadley · Sep 8, 2011

Re: Repitch

Correct. Pitch is measured in inches not degrees. When someone talks about a degree of pitch it can be confusing. It should be an inch of pitch rather than a degree of pitch. Rake is measured in degrees so it can be confusing.

V153 · Sep 8, 2011

Re: Repitch

Dhadley said:
When someone talks about a degree of pitch it can be confusing. It should be an inch of pitch rather than a degree of pitch. Rake is measured in degrees so it can be confusing.

No disagreement here but when you try to use inches of pitch & inches of diameter in the same sentence some people get really confused. 'Specially if the numbers are close to each other ...

Bondo · Sep 8, 2011

Re: Repitch

V153 said:
No disagreement here but when you try to use inches of pitch & inches of diameter in the same sentence some people get really confused. 'Specially if the numbers are close to each other ...

Ayuh,... Really,..??
Standard prop terminology that I see, prop sizes are stated as Diameter, in inches, by Pitch, in inches...
Such as 14, 1/2" X 21" for a Mercruiser sized prop...

I agree with Dhadley, callin' pitch in degrees, only confuses an issue that many/ most are confused by from the start...

V153 · Sep 8, 2011

Re: Repitch

Bond-o said:
I agree with Dhadley, callin' pitch in degrees, only confuses an issue that many/ most are confused by from the start...

I reiterate I don't disagree. Just sayin'. You say 'pitch' to me'n I assume your discussing degree of rake. But that doesn't mean near the same thing to the average prop customer?

Y'know before I really got into boating I thought pitch was that black molten goo they pour on tar roofs. Or something that happened during a baseball game ...?

Dhadley · Sep 8, 2011

Re: Repitch

Pitch and rake are two totally different things that have very different effects on what a prop does.

Bondo · Sep 8, 2011

Re: Repitch

Y'know before I really got into boating I thought pitch was that black molten goo they pour on tar roofs. Or something that happened during a baseball game ...?

Ayuh,... Growin' up in Maine,...
Pitch is the gooey crap that falls outa Pine Trees, 'n a Great card game....

Scott Danforth · Sep 8, 2011

Re: Repitch

stickerhard said:
I have a 15 pitch Stelletto prop and I was wondering can a prop shop change the pitch by 1 or 2. The prob I got is it at the top of the rpm band and just seems to slip more then my factor alum.

to answer your question. yes, a prop shop can re-pitch up/down by 1 or 2 (usually 2)

is it worth it, not sure, you have to get a quote.

Sprky · Sep 8, 2011

Re: Repitch

You cannot get 2" out of a repitch. You are doing good to get 1". Anyone telling you otherwise is blowing smoke up your ...................

Pitch is the theoretical distance a prop will travel thru a solid per one revolution. Ayuh!

chriscraft254 · Sep 8, 2011

Re: Repitch

If you want more speed per rpm, buy some Nauticus smart tabs! Simply put, they will do alot more for you than changing your prop pitch again! By the way, they only cost about $100 for your size boat, cheaper than a cheap prop.

stickerhard said:
i have a 15 foot runabout fibergalss and a 1979 80 hp merc . I had a 17 pitch alum on it before and would run about 5,000 rpm's and now with the 3 blade stelleto it runs close to 5700 rpms.It just feels like its slipping and not catching ahold like the alum did.I dont have a gps but i have a buddy with a 18 foot trihaul with a 115 rude on it and he used to run away from me now we are about dead even. But I think i could do better if it was cupped different or one pitch higher. I didnt know if they can do that or i need to try a different prop. thanks for the help

Sprky · Sep 9, 2011

Re: Repitch

chriscraft254 said:
If you want more speed per rpm, buy some Nauticus smart tabs! Simply put, they will do alot more for you than changing your prop pitch again!

Please explain how pushing the bow down and increasing drag, creates more speed?

chriscraft254 · Sep 9, 2011

Re: Repitch

I didn't say anything about pushing the bow down or producing drag. But since you asked, Its all about boat attitude and providing the best possible axis so your boat can perform the way it should. Man, I have explained this a thousand times, now I am just referring people to this link. http://www.nauticusinc.com/pdf/nauticus_smart_tabs_tech_info.pdf

If your truly interested in edjucating yourself on boat attitude this link is a great place to start. I have had these on my boat for two years now and can attest to the performance is unreal with these installed. Every claim Nauticus makes and Guarantees is spot on plus some. I will continue to recommend them to anyone that has issues performance wise in any regard. They are definately worth a look, plus the link a supplied is kinda hidden on there web site, I think it should be one there home page. Check it out, its a good read with diagrams with explainations.

If you don't understand or don't have the answer to you questions after reading the link, I will be more than happy to discuss it further.

Sprky said:
Please explain how pushing the bow down and increasing drag, creates more speed?

V153 · Sep 9, 2011

Re: Repitch

Sprky said:
You cannot get 2" out of a repitch. You are doing good to get 1". Anyone telling you otherwise is blowing smoke up your ...

Agreed. Shops round here won't guarantee trying to bend more than an inch, up or down, into a SS prop.

Sprky · Sep 9, 2011

Re: Repitch

Chris, those are built for people just like you.

Either you don't understand hydrodynamics or your a salesman for the company.

Repitch

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