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Help me pick a prop for 17 ri237

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Darkside    248

I am not dissatisfied enough with current prop at this time to justify the $$ for a bigger prop. Would I like to try it yes, at this point am I willing to spend $800 On a prop, No....

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wheels    147

from my experience and everything I can find online its 200 per inch.

 

"If you're changing pitch on a recreational boat, remember that each inch of pitch is worth about 200 rpm. Lowering the pitch will increase rpm and vice versa. For example, going from a 23 pitch to a 21 pitch will increase engine rpm by about 400 revolutions."

 

"Increasing pitch reduces rpm and reducing pitch increases rpm. A 1" change in pitch will usually result in a 200 RPM change in engine speed. Therefore, if your engine operates below the optimum proper rpm, you should consider a boat propeller with less pitch. If your engine over-revs, consider increasing the pitch."

 

^ That being said increasing the pitch by 2" (13" to 15") would drop it 400 and add 200rpms by adding 1" diameter (surface area)

 

 

 

 

Also Ive changed props on 2 different surf boats keeping the pitch but going up 1" in diameter and it has increased rpms by 200ish on both. For some reason its always different on different boats though lol. they only way to know for sure is to try!

 

ive tried tons of props on tons of boats and this is what ive found to be true. Just my opinion though and the numbers are estimated theoretically. I used to have a spreadsheet to calculate it but lost a backup HD and cant find it anymore :(

 

I completely aggre with you on your pitch numbers

 

You're diameter numbers do not make sense. Think of it as the same way of putting bigger tires on your truck, if you went from a 33" tire to a 34" tire your rpms would be lower at the same Hwy cruising speed because your bigger tire is having to do less revolutions per mile. Every site I google says rpm drops by 400 to 500 rpm per 1" diameter increase. If you have replaced a prop on your boat with exact same pitch but 1" larger diameter and your rpms went up that defies the laws of physics.

Edited by wheels

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Lak3surf3r    712

I am not dissatisfied enough with current prop at this time to justify the $$ for a bigger prop. Would I like to try it yes, at this point am I willing to spend $800 On a prop, No....

see what props Century has in stock and they will let you try them. the 1st RI257 Joe. Youre the guinea pig now. thems the rules, of the site ;) i kid i kid

 

I completely aggre with you on your pitch numbers

 

You're diameter numbers do not make sense. Think of it as the same way of putting bigger tires on your truck, if you went from a 33" tire to a 34" tire your rpms would be lower at the same Hwy cruising speed because your bigger tire is having to do less revolutions per mile. Every site I google says rpm drops by 400 to 500 rpm per 1" diameter increase. If you have replaced a prop on your. Pat with exact same pitch but 1" larger diameter and your rpms went up that defies the laws of physics.

 

I know lol I agree, but thatss what happened both on my v226 and my ri237! It could have been because of slip/drag/cavitation and or not enough clearance though.

 

For some reason its always different on different boats though (inconsistent mounting and angles from boat manufacturers) lol. they only way to know for sure is to try! we have traded props on 2 different RI237s and got different numbers on each of them... and they were only 1 build slot away from each other!

 

And sorry, I misread your 1st post that said 200 rpm per 1" and i was thinking 400 per 2" but misread it as 200 per 2" lol same thing different wording. long day!

 

supposedly that couldnt happen though!

 

"Mercury's website offers this advise:

Adding 1 inch of propeller pitch will reduce full-throttle RPM by 150 to 200. BUT There is no direct correlation between diameter and rpm as there is for pitch. That is why you will not find any recommendations relating to it vs rpm"

Edited by Lak3surf3r

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wheels    147

see what props Century has in stock and they will let you try them. the 1st RI257 Joe. Youre the guinea pig now. thems the rules, of the site ;) i kid i kid

 

 

I know lol I agree, but thatss what happened both on my v226 and my ri237! It could have been because of slip/drag/cavitation and or not enough clearance though.

 

For some reason its always different on different boats though (inconsistent mounting and angles from boat manufacturers) lol. they only way to know for sure is to try! we have traded props on 2 different RI237s and got different numbers on each of them... and they were only 1 build slot away from each other!

 

And sorry, I misread your 1st post that said 200 rpm per 1" and i was thinking 400 per 2" but misread it as 200 per 2" lol samething different wording. long day!

Yeah no boat is the same and slip will play a big factor and cup will make minor differences. This was the biggest hurdle in ordering my ri237, I think centurion and my dealer were ready to drop a propeller on my head, lol. Mine is coming with the 2277 which is 15x15.75. I will post up my numbers when I get the boat on the water with full ballast and lead. I really have high hopes to get my surf rpm around 3600 rpm with full weight and 4 to 6 people. I am at 900 feet above seal leavel so at least I'm not fighting elevation.

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Lak3surf3r    712

Yeah no boat is the same and slip will play a big factor and cup will make minor differences. This was the biggest hurdle in ordering my ri237, I think centurion and my dealer were ready to drop a propeller on my head, lol. Mine is coming with the 2277 which is 15x15.75. I will post up my numbers when I get the boat on the water with full ballast and lead. I really have high hopes to get my surf rpm around 3600 rpm with full weight and 4 to 6 people. I am at 900 feet above seal leavel so at least I'm not fighting elevation.

Post em up! You have the new shaft angle right? Ive had better luck retooling and adding more cup than increasing diameter but hopefully that 15" diameter with the higher pitch and the .150 cup will get your rpms down there! My 14.5x14.5 .105 cup on my 16' 237 at 1500ft ran at 4200-4300rpms with 3-4 people and 300#s of lead in it but didnt take any bow weight with the old shaft angle.

 

The two 237s that we swapped props on the QS tabs were mounted 1/4 differently and the rams also didnt extend the same lengths either so im sure that played into the wonky rpm numbers as well. I wish we would have measured the shaft angles as well now.

Edited by Lak3surf3r

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wheels    147

Lake,not to beat a dead horse but here is a quote from your original ri237 prop thread.

 

It was about 4400-4600 rpm with full ballast, QS, 700lbs of lead (we threw my buddies 400lbs in that day just for fun to make the wave massive) and 10 ppl at 12mph. regularly its between 4000-4200 with my 300lbs of lead and 6 ppl at 11.6mph. Keep in mind that every 1" of pitch that you go down will take your rpms up by 200 and also for every 1" of diameter that you go up takes your rpms down by 200.

 

Another member then corrected you saying it was actually 400rpm change for an inch of diameter.

 

Like I said I researched the hell out of the ri237 before my order. Your posts were definitely the most informative on the boat and I don't believe anyone else is More informed than you on the ri. Thanks for all your posts and set up's in the forum but now you have me even more confused. Haha.

 

Like I said I just have to get mine in the water and experiment. Thanks for your settings though cause I will definitely start with using those.

Edited by wheels
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Lak3surf3r    712

Lake,not to beat a dead horse but here is a quote from your original ri237 prop thread.

 

It was about 4400-4600 rpm with full ballast, QS, 700lbs of lead (we threw my buddies 400lbs in that day just for fun to make the wave massive) and 10 ppl at 12mph. regularly its between 4000-4200 with my 300lbs of lead and 6 ppl at 11.6mph. Keep in mind that every 1" of pitch that you go down will take your rpms up by 200 and also for every 1" of diameter that you go up takes your rpms down by 200.

 

Another member then corrected you saying it was actually 400rpm change for an inch of diameter.

 

Like I said I researched the hell out of the ri237 before my order. Your posts were definitely the most informative on the boat and I don't believe anyone else is More informed than you on the ri. Thanks for all your posts and set up's in the forum but now you have me even more confused. Haha.

 

Like I said I just have to get mine in the water and experiment. Thanks for your settings though cause I will definitely start with using those.

 

Haha thx, *disclaimer* on that post I was Ctrl C and Ctrl V'ing googles findings for the rpms not my own. I didnt want to defy physics like a few of my numbers/boats have (not really because I blame cavitation/drag/slip for my anomalies lol). After I swapped a prop with a friend later that year it gave me the 200 rpm increase going up 1". Like I said my boat was early off the line (i think it was #4) and had very different measurements that any other 237 comparatively. As was my 2012.5 V226 that had half fineline half Calabria manufactured parts in it (the other boat that this rpm anomaly happened in). Those were the only 2 boats I tried an increase in diameter in though, the rest were just pitch.

Edited by Lak3surf3r

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Darkside    248

I have played the prop game in the past as well. The biggest factor in going up in diameter is it theoretically should reduce prop slip as there is more surface area to grab the water.

However you get nothing for free, it takes more torque to twist that larger propeller. So you have to find the balance between diameter, pitch and your engine power curve.

So again if I go 17x15 that should net 800 RPM, but if the H6 doesn't have the grunt at 3200 to spin it the engine will load up and work harder. This is why it is also important to make sure you can hit redline with your prop. If WOT is running 4200 RPM your over propped and need to dump weight, or go less aggressive prop.

The other piece is as you goo up in diameter the greater the drag, because the surface of the prop is increasing, so is the resistance it inherently creates. At the same time I have always heard you increase potential for slip and cavitation when pitch exceeds diameter...

Edited by Darkside
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carguy79ta    66

Darkside are you considering getting a 17" prop? I agree with the SWAG of 800 RPM on your 17x15. might be too agressive...maybe 17x14? what RPM were you surfing at Saturday? I have the same prop coming that you have. also did you try to go to WOT under load?

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Darkside    248

I was running 4000 RPM port 3800 starboard, I did not take to WOT while fully weighted. Empty yes top speed 33!

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MrHudson13    8

I run a 15x14.25 on my 2017 Ri237 and it's awesome compared to my 2016 where I ran 14.5x14.25. It reduced rpm by 200-300. Stoked the 2017 allows for larger props. ?

Edited by MrHudson13
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wheels    147
16 minutes ago, MrHudson13 said:

I run a 15x14.25 on my 2017 Ri237 and it's awesome compared to my 2016 where I ran 14.5x14.25. It reduced rpm by 200-300. Stoked the 2017 allows for larger props. ?

So what rpm are you surfing at and what speed? What elevation are you at? And what motor?

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MistyCreek    3

Has anyone tried the 17x14 on the xr7 in a 257?  With a h6 at low altitude?  (Should be similar result). My dealer is saying that the 16x15 is fantastic at elevation for both motor configurations,  but I would like some data/experience on the 17x14 before I settle in on the 16" wheel.  In was hoping dealer would get it tested prior to our 257's delivery date but it is looking unlikely.  Our boat will have the xr7 motor.  Any info at all would be appreciated.

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DarksideR    1,676

Here's my buddies findings with his 2017 Ri237. He dropped between 400-700RPM depending how he setup his ballast. Also noticed running the boat more even weighted reduced the RPMs even though the total ballast #s went up over listed setup.

 

 

 

Ok 

Had the 1235

14.5x14.25
.109 cup

Have now 2277

15x15.75 
.150 cup

The 1589 is a good one too

14.5x16
.135 cup

Acme explained to me for every inch of pitch is worth 200 rpm less. But if u go up in prop size u also gain less rpm too. This is speaking for a set up like mine with the vdrive reduction. 

I might try a 15.5x15.5 #2849

Having the gear reduction gives me I think options ?

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MrHudson13    8
On 4/30/2017 at 9:55 PM, wheels said:

So what rpm are you surfing at and what speed? What elevation are you at? And what motor?

I surf around 11.4 and with about 4 people and 500lbs of lead I run 3800-4000 rpm at 3700'. I have the H6.

Edited by MrHudson13
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LT66tx    0

has there been any updates on the 2017 ri237 recomendations? I have a stock 1235 14.5x14.25.  .109 cup. I will be surfing and wake  boarding with 6 to 8 people and 900 feet above elevation H6 motor. Stock ballast. what is the largest diameter with no burn?

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wheels    147

16x15 i found to be the best for me. I tried the 16x13 and it’s a great prop but more than I needed at 900ft and the h6 motor. 16x13 I was running 3800 to 4000 rpm and 16x15 I’m running 3400. 14.5” prop is way to small for that boat. Mine came stock with 15”x 15.75. 

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SurfOsoyoos    0

They come with 16x15 and 16x13. I am curious to see how my 257 will do with the H6 ...

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wheels    147
17 hours ago, SurfOsoyoos said:

They come with 16x15 and 16x13. I am curious to see how my 257 will do with the H6 ...

We gonna see a 257 on the lake next year? That’s gonna have a few guys jealous. 

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SurfOsoyoos    0
On 12/5/2018 at 8:24 AM, wheels said:

We gonna see a 257 on the lake next year? That’s gonna have a few guys jealous. 

Of course man! I have a feeling there will be a couple more 257s in 2020 after being the only 57 in the surf group...

You're always welcome to join!  It will split its time between Osoyoos and Lower Mainland.  
 

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wheels    147
7 hours ago, SurfOsoyoos said:

Of course man! I have a feeling there will be a couple more 257s in 2020 after being the only 57 in the surf group...

You're always welcome to join!  It will split its time between Osoyoos and Lower Mainland.  
 

Where you stay In Osoyoos? My ri spends the whole season at Casa Del Lago. You buy the new boat from wizard?

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