Help me pick a prop for 17 ri237

[Lak3surf3r 714]

No prop burn. 143 hours of use. About half with this prop. Started with a 15", wanted as big as possible for better cruising speed and lower surf rpm. Mission accomplished. Yes, original prop angle.

Thats impressive! Do you have a pic of the prop to show the clearance with that 15.5 on it?

[Darkside 248]

I have the H6 and surf prop (16x13) on my 257. It handled everything we threw at it with ease! Never once did I feel a lack of power. Surf RPM 4000 regular 3800 goofy, this is likely due to different quicksurf, stinger, etc between sides. Downsides...4000 RPM at 23 Mph cruising. Top speed 33. I would be very interested in trying a 17x15 or 17x17. However this is going to be very low on my priority list.

[Lak3surf3r 714]

I have the H6 and surf prop (16x13) on my 257. It handled everything we threw at it with ease! Never once did I feel a lack of power. Surf RPM 4000 regular 3800 goofy, this is likely due to different quicksurf, stinger, etc between sides. Downsides...4000 RPM at 23 Mph cruising. Top speed 33. I would be very interested in trying a 17x15 or 17x17. However this is going to be very low on my priority list.

 

Joe, make sure you have them to try before you buy 1st. By my math if you were at 4000rpms on the Port (the only) side that counts and went to a 17x15 it would only lower you to 3800rpms (4000-400 for 2" of pitch + 200 for gaining 1" diameter) or for the 17x17 would put you at 3400rpms (4000-800 for 4" of pitch + 200 for gaining 1" diameter). But moving up to 17" diameter with more surface area while changing that much in pitch also increases your chances of cavitation on that heavy of a boat (15k of ballast, gas, people, and the boat weight). If I were you I would try a 16x15 or something close to that if that is an option and see if it works as that should drop you 400rpms before going up to a 17"

Edited March 6, 2017 by Lak3surf3r

[wheels 151]

 

Joe, make sure you have them to try before you buy 1st. By my math if you were at 4000rpms on the Port (the only) side that counts and went to a 17x15 it would only lower you to 3800rpms (4000-400 for 2" of pitch + 200 for gaining 1" diameter) or for the 17x17 would put you at 3400rpms (4000-800 for 4" of pitch + 200 for gaining 1" diameter). But moving up to 17" diameter with more surface area while changing that much in pitch also increases your chances of cavitation on that heavy of a boat (15k of ballast, gas, people, and the boat weight). If I were you I would try a 16x15 or something close to that if that is an option and see if it works as that should drop you 400rpms before going up to a 17"

Lake you have the diameter Rpm's backwards

 

For every 1" of diameter you increase you would drop 400(approximately) rpm

For every 1" of pitch you increase you would drop 200 rpm

So he would be theoretically at 3200 rpm. With the 17x15. I do not think the 17x7 would work at all with 1.72 gear ration on ri257

The non surf prop 16x15 may just be the right prop for the ri257 as long as it can get it up to surf sped with out a struggle. It would be around 3600 rpm. In 17" you would want a 17x13 or 17x14 in theory

Edited March 6, 2017 by wheels

[Lak3surf3r 714]

Lake you have the diameter Rpm's backwards

 

For every 1" of diameter you increase you would drop 400(approximately) rpm

For every 1" of pitch you increase you would drop 200 rpm

So he would be theoretically at 3200 rpm. With the 17x15. I do not think the 17x7 would work at all with 1.72 gear ration on ri257

Agreed, i doubt the 17x17 would even work on that 257

 

 

"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 (possibly just because of slip and drag). 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

 

Edited March 6, 2017 by Lak3surf3r

[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....

[wheels 151]

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 March 7, 2017 by wheels

[Lak3surf3r 714]

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 March 7, 2017 by Lak3surf3r

[wheels 151]

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.

[Lak3surf3r 714]

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 March 7, 2017 by Lak3surf3r

[wheels 151]

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 March 7, 2017 by wheels

[Lak3surf3r 714]

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 March 7, 2017 by Lak3surf3r

[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 March 7, 2017 by Darkside

[carguy79ta 67]

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?

[Darkside 248]

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

[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 May 1, 2017 by MrHudson13

[wheels 151]

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?

[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.

[DarksideR 1,679]

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 ?

[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 May 8, 2017 by MrHudson13