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sunvalleylaw

Prop for my new to me '98 Response LX

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sunvalleylaw

Our boat will be used primarily for slalom skiing, some wake boarding.  Occasional family tubing.  At 5800 feet of elevation at Magic Res. in Idaho, and at 6547' at Redfish Lake, also in Idaho.  Alturas and Petit lakes would be about the same as Redfish.  It currently has a 13x13 4 [EDIT:  Incorrect.  It is a 3 blade 13x13] blade prop that appears to be stainless steel, and is marked "VP".  Think this will work?  Or will I need to change props?  I will not likely be doing a bunch of surfing, have no wedge, and no weight bags or anything.  We will keep the boat load down with half a tank of fuel, and 2 or 3 max people with skier.  

 

Thanks!

I should be able to upload a pic of the prop on Sunday when I pick the boat up if that helps.  

Edited by sunvalleylaw

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Sethro

My guess is you'd be after a 13x11.5 (Acme or OJ) CNC prop, given the elevation.  Maybe someone at a high elevation can chime in, or call Acme or OJ as they are both known for excellent customer service in helping you select the correct prop for your application.  I wouldn't run that CVP stainless prop much, they are known for "throwing a blade" at speed which can cause some significant damage underneath.  I have an OJ 13x12 and just acquired an Acme 13x11.5 but don't run the boat at any elevation to speak of.

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85 Barefoot

SVL, I happen to have an ACME 515 (13x12) that should be fine and was standard issue for that boat for years.  It has been reworked one time and is in great condition.  let me know if interested.

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Woodski

@sunvalleylaw:  Standard issue on that boat was a 3 blade stainless CVP in the day, 4 blade geared more towards slower speed activities such as wakeboarding.  CVP is out of business but they were decent props in the day other than as noted, would sling a blade occasionally.  When the CNC props came to market, the Response prop at sea level was the Acme 515, higher elevations may require a slight pitch reduction for optimum performance.  At the altitudes you note, the engine will be producing between 80-83% of peak sea level power, so consider that when selecting new prop. 

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85 Barefoot

SVL, wood is correct on all accounts, but if you're open water skiing with a crew of 2-3, 515 should be fine.  For a private ski lake (like the one in Bellevue) with short setups, and really good skiers who are used to the hammer being put down on them, a 13x11 or so might be better, but for what you're describing 13x12 should be fine.

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sunvalleylaw
On 8/8/2016 at 9:19 AM, Woodski said:

@sunvalleylaw:  Standard issue on that boat was a 3 blade stainless CVP in the day, 4 blade geared more towards slower speed activities such as wakeboarding.  CVP is out of business but they were decent props in the day other than as noted, would sling a blade occasionally.  When the CNC props came to market, the Response prop at sea level was the Acme 515, higher elevations may require a slight pitch reduction for optimum performance.  At the altitudes you note, the engine will be producing between 80-83% of peak sea level power, so consider that when selecting new prop. 

Thanks!  As it turns out, I was incorrect as the boat was still at the former owners when I posted, and I believe it still has the standard issue 3 blade 13x13.  Thanks for the other insights.  

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sunvalleylaw
On 8/8/2016 at 9:41 AM, 85 Barefoot said:

SVL, wood is correct on all accounts, but if you're open water skiing with a crew of 2-3, 515 should be fine.  For a private ski lake (like the one in Bellevue) with short setups, and really good skiers who are used to the hammer being put down on them, a 13x11 or so might be better, but for what you're describing 13x12 should be fine.

Thanks 85 Barefoot.  You sound familiar with the area.  My boat will not be getting on the Bellevue lake any time soon.  I did have hopes of getting a part membership there for some tows at one point though.  Best I can do for course skiing is probably Cordeau's course at East Magic.  I also have a friend down at Black Butte out of Shoshone where I can ski course, but I typically would just give gas money and use his boat down there.  My boat will be mostly for Magic, and up at Redfish and the Mountain lakes.  Maybe the best thing to do is go see what my WOT is up at Redfish, and Magic, and go from there WRT what adjustments to RPM's I might need.  Does that sound right?  WRT the original prop, the original owner (William Bonney, AWSA judge and ski instructor) has run that thing since 1998 without issue, so hopefully it will not throw a blade in the short time is use it to check things out.  

Edited by sunvalleylaw

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sunvalleylaw

Also, can anyone tell me what the expected WOT RPM range is for this 1998 Malibu Response LX with the 325 5.7 Indmar?  That would help me verify the prop I should use I would guess.  

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Sethro

My boat, in Northern IL, turns only about 4500-4600 with an OJ 13x12 but I'm not sure what cup it has.  With my newly acquired (but used) ACME 13x11.5 it turns 4900-5000 RPM.  Both props are yielding about 46 mph with the 13x11.5 about 200 more rpms at 20, 34, and 36 mph.  The ACME seems noticeably quicker, but I have no data to prove it.  The CVP 13x13 also turned around 5000 rpm when I used that in years past.

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footndale
39 minutes ago, roeboat said:

I would stick with the stock prop because Malibu knows how to prop their boats. If you really want to change your prop I would try this one http://www.waterskis.com/1216B-p/13x13_4_blade_propeller_force.htm

Except it is stainless, which is not one of Malibu's best decisions at the time.  They blow up and shred the hull.

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Woodski

@sunvalleylaw:  WOT on three Responses on our lake (96,97,07) range from 4700-4900 RPM with top speeds 47-49 mph.  Two were CVP propped and one Acme, elevation 962' and tests tended to be done in 70 degree(ish) temps.  Both water and air temp have pretty significant effects on performance. 

On the CVP prop, they offered three variations on the 13x13 3 blade: std, M & MD which should be stamped on the hub after the 13 x 13, if nothing it is standard.  The difference is slight pitch increase for M and again for MD making it pretty close to 13 x 14.  I did a lot of detailed testing and prop comparisons just as the Acme was coming out and other options included a stainless Cutter (which was a CVP clone).  To preface my test results, I had worked over my CVP M so it was excellent (sharpened the leading & trailing edges, roughed the surface for grip, verified balance) because I bumped my power level up and could cavitate the original Dymex prop.  For a decent comparison for today's prop market, I did get the chance to do an A-B (or A-C in this case) prop comparison for acceleration / WOT / time to distance / RPM v boat speed.  Results were as follows:  the Acme pulled + 1 mph (@ 250 less RPM) WOT long run, was slightly slower to 250' (.1 sec) but slightly faster to 600' (.15 sec).  Both props worked great, my analysis indicated the pitch difference was really the difference in results, Acme having more actual pitch even though not indicated as such in the literature.  One caveat, when I roughed up the smooth stainless blades it made a significant improvement in prop performance as did making sure the edges were nice and sharp (I am sure the errant fish might not have liked that part).  Also, as an FYI my boat has the SV23 hull so results should be pretty comparable, but more HP at my disposal (I have modified my engine) so exact prop choice might be slightly different.

In conclusion, I would not sweat the CVP prop, go out and do some testing to see if it meets your needs then consider if a prop change is needed.  One suggestion, for your running at higher altitudes if an issue, consider getting cool, fresh air to the air cleaner via removing the cup holders in the engine box and even running some cold air tubes to the air cleaner.  Hot air, which rises up in the engine box is less dense (similar effect by going up in elevation) so reduces performance compared to ambient.  Unless you have a short setup or plan to do some serious barefooting (which I highly suggest you do with that boat, it is one of the better hulls for footing), you should be fine.  Go have fun!

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85 Barefoot
2 hours ago, Woodski said:

@sunvalleylaw:  WOT on three Responses on our lake (96,97,07) range from 4700-4900 RPM with top speeds 47-49 mph.  Two were CVP propped and one Acme, elevation 962' and tests tended to be done in 70 degree(ish) temps.  Both water and air temp have pretty significant effects on performance. 

On the CVP prop, they offered three variations on the 13x13 3 blade: std, M & MD which should be stamped on the hub after the 13 x 13, if nothing it is standard.  The difference is slight pitch increase for M and again for MD making it pretty close to 13 x 14.  I did a lot of detailed testing and prop comparisons just as the Acme was coming out and other options included a stainless Cutter (which was a CVP clone).  To preface my test results, I had worked over my CVP M so it was excellent (sharpened the leading & trailing edges, roughed the surface for grip, verified balance) because I bumped my power level up and could cavitate the original Dymex prop.  For a decent comparison for today's prop market, I did get the chance to do an A-B (or A-C in this case) prop comparison for acceleration / WOT / time to distance / RPM v boat speed.  Results were as follows:  the Acme pulled + 1 mph (@ 250 less RPM) WOT long run, was slightly slower to 250' (.1 sec) but slightly faster to 600' (.15 sec).  Both props worked great, my analysis indicated the pitch difference was really the difference in results, Acme having more actual pitch even though not indicated as such in the literature.  One caveat, when I roughed up the smooth stainless blades it made a significant improvement in prop performance as did making sure the edges were nice and sharp (I am sure the errant fish might not have liked that part).  Also, as an FYI my boat has the SV23 hull so results should be pretty comparable, but more HP at my disposal (I have modified my engine) so exact prop choice might be slightly different.

In conclusion, I would not sweat the CVP prop, go out and do some testing to see if it meets your needs then consider if a prop change is needed.  One suggestion, for your running at higher altitudes if an issue, consider getting cool, fresh air to the air cleaner via removing the cup holders in the engine box and even running some cold air tubes to the air cleaner.  Hot air, which rises up in the engine box is less dense (similar effect by going up in elevation) so reduces performance compared to ambient.  Unless you have a short setup or plan to do some serious barefooting (which I highly suggest you do with that boat, it is one of the better hulls for footing), you should be fine.  Go have fun!

 

Wood is a great source of info, and I'm not "disagreeing" with him, but the underlined above is what everyone has said to themselves before it lets go.  Redfish lake is glacier cold and 300 feet deep.  I don't want to scare SVL, but I'd be remiss not to mention this issue as others have as well.

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Woodski

My comment was based on performance, not reliability, so @85 Barefoot brings up a very valid point.  You could take your prop and have it magnufluxed and at the very least I would inspect the blade to hub area for any cracks as that is where they 'separate' and send the errant blade to Davy Jones locker (see my initial comment mentioning that issue).  FWIW - there are 4 boats on my lake that used a CVP prop, one kicked a blade (which requires a tow or prop change due to total imbalance at that point), you can do the % although not sure it simply failed or due to hitting a snapping turtle which we do at least once a year, the only other one now with a CVP is sill going.  BTW - my finely tuned CVP is a spare...perhaps that says it all.

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sunvalleylaw

Well, I will risk it enough to test it out at Magic Reservoir, maybe tomorrow morning.  Not quite as cold, not quite as deep.  Not quite as high.  4800 vs. 6500.  Will see what RPM's I am getting after we are good and warmed up.  Then go from there.  Am thinking it will end up being a choice between a 515 and 525 or something like that.  

Edited by sunvalleylaw

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sunvalleylaw

So tried it out today.  At 4800 feet, I got 43-44 MPH out of it, which is what prior owner said he was getting.  WOT was 4500 RPM, with three in the boat and about a half full tank of gas.  So, works as advertised by prior owner at this altitude.  Hole shot was fine, pulled well for a ski at 34, and at about 17 for my daughter on our wakeboard.  Hope to get up to the higher lake this weekend to see if there is a performance drop.  Thinking the 515 might work if there is not a big performance drop with the extra 700 feet of elevation to the other lakes.  

Edited by sunvalleylaw

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85 Barefoot

what engine do you have?  

If monsoon, ideal RPM range is 4800-5200 as I recall at WOT.  While I don't think you're going to ruin it overnight, you should prop it so you hit your recommended range.

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sunvalleylaw

Monsoon 325.  FWIW, this seems to be close to the RPM range prior owner was getting.  His BTS/SL Cruise speed control numbers were about 3300 at 36, 3110 at 34, at least when the system was set up on 5/28/2000. Seemed like the boat was at about 3300 to 3400 or so at 34 today.  

EDIT:  SO, I do not know if those RPM measurements are still accurate for what he was getting.  He loved that speed control system and said it kept him right on the money in terms of speed, but he has been a bit vague on the RPMs and thought he was just guessing.  When I texted him if he knew his WOT, he did not, but said his best guess as to RPMs at 34 was about 3300, which was close to what I got today.  Not sure if I might not also need an injector cleanse as suggested elsewhere.  I doubt I will do any significant motor modification for altitude, as it pulls just fine for our needs.  Just get it tuned up if necessary, and happy.  It sure sounded happy today, and operated smoothly and well.  So, maybe a tune up, and figuring out the prop, and should be set.  

Edited by sunvalleylaw

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85 Barefoot

SVL, there would be no reason for the correlation of rpm and speed to change.  that's constant across altitudes.  But I can confidently say that boat is overpropped at your altitude if you're just hitting 4500.  Again, not like its going to blow up next time, but the long term risk of overpropping is you do create premature engine wear.

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sunvalleylaw

Hmm.  Not sure I love that answer (NOT saying incorrect, just worries me) as this boat has had this same prop for many years.  The boat has been used very regularly for teaching skiing by prior owner.  Oh well, what is done is done, and I bought the thing.  It seems to run well, and seems strong.  So hopefully it is in good shape.  Not sure how I would check that.  The motor looks good, oil seems good, and seems to be running just fine.  Starts easily, settles into a nice idle, and as I said, does the rest fine too.  Hmm.  

Edited by sunvalleylaw

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85 Barefoot

SVL, I'm not trying to scare you.  If you called Indmar and asked them if you're overpropped, I'm confident they'd say yes, but don't rely on me, everyone at Indmar is great and will help you or your manual will tell you the recommended WOT range.  I wouldn't be "worried", but the boat will perform better with a more shallow prop.  

 

I'll get back to your Pm.

Edited by 85 Barefoot

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Woodski

@sunvalleylaw:  I tend to agree with '85, the prop seems a touch tall given the RPM/speed numbers you quote other than the 3300 @ 34 as that sounds pretty good and don't assume tachometer is exactly accurate.  Typically, a tourney ski boat of this vintage is propped to do very close to 100 RPM / 1 mph of slightly less.  With your boating locations being at higher altitude, the tendency is to reduce pitch a bit to compensate for less air density.  For basic boating, that prop won't hurt anything, I wouldn't do lots of WOT running but for mid throttle skiing, etc. it will be fine.  I think you need to take a good look at the prop and see if it is either a base 13 or a 13M or 13MD as that will provide better guidance on you next prop selection.  Given your altitude, I would certainly consider a 525.  If the RPM/speed ratio aligns with my testing, you can pretty much do a quick calculation to see what a 515 would do.

I would guess it is in good shape, if you want to confirm, simply do a compression and leak down test.  The Monsoon is pretty much a bullet proof engine and will provide many hours of great running.  Make sure you keep supplying it with fresh water (impeller), clean gas (good filters) and annual oil/filter changes & you should have many years of happy boating.

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sunvalleylaw

@Woodski , thanks.  That was about what this boat seemed to be doing today.  The speed lagged just slightly behind the RPMs at WOT.  But was fairly close to 100 RPM / 1 MPH.  Within a range.  I think either the 515 or 525 will be what I am after.  I will see what I can figure with some calculations.  Any links or resources for me to figure out how to do that?

I want to try it up at the highest altitude I will be running and see how the hole shot is, etc.  Will NOT run WOT for long.  No need to.  Redfish is the largest lake I will run and it is not huge.  I am used to cruising in the low 30's most of the time for lake crossing.  So since I will ski course at Magic, and the lower elevation where I was today, the 13x12 might do me.  But will stay open minded for a bit as I get to know the boat.  The boat is now running non-ethanol 91 which is sold at the local gas station where I fill in Hailey.  

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edwin

Lots of good info in this thread.  I've spent a ton of time testing props over the years and have found that there's a ton of variables in play - Altitude as you've mentioned, weight in the boat, size and technique of the guy at the end of the rope, the kind of pull the skier wants, etc.  My gut tells me the 13x11.5 ACME is gonna be your prop 

Edited by edwin
typo

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