Power to the propeller!

[Jody_Seal]

For the last number of years or since the advent of Zero Off I have been trying to find ways to eliminate the Zoom feeling that Zero off gives me going into and off the wakes . Setting's do not seem to help just moves the Zoom elsewhere in the work Zone Process. What I call the zoom is the feeling and consequences that happens with us skiers that don't really have the "good" slalom technique that the ZO system was designed for. Also the bigger slalom skier with old school technique that tend to get deep at the buoy can get zoomed as the system has a real tendency to over react. After being slammed into the wake and zoomed out of control off the second side Because I was not as stacked as I could be or in layman's terms had my Ass dragging and trying to get to the next buoy nor getting the chance to get the ski back under me as ZO will not allow that. I felt that their has to be a way to minimize the crappy feel of ZO for skiers such as myself. Keep in mind we used to be able to get the job done with the previous speed control (Perfect Pass) as the score book did not care what it looked like.

 

After trying to analyze and manipulate the system to minimize the Zoom feel by Toning or running slower in practice mode I decided to take a look at how the power is being transmitted to the water, what I found was that in a lot of cases propeller slip was not my friend in this process and that a propeller with less slip tended to not give me that Zoom feeling. One Boat company that Runs the OJ products did not give me that Zoom feeling when skiing behind their boats however the other two did.....

With today's modern tournament boats they are bigger and heavier then that of the tournament boats we had 10 years ago, they have more HP and are in most way's less efficient then earlier models. Having a propeller that has to some degree increased slip will allow for the motor to run up a bit before it bites and holds firm getting these bigger boats up and down the lake. Now Propeller technology in a ski boat is still a Black art akin to alchemy in my mind however we do have combinations and a few known's that have made the boats be as efficient as current rules dictate. I guess where I am going is that most of the manufacturers of our boats currently being used are not considering how the prop works in conjunction with that of the speed control and overall skier feel. 16.95 or 16.08 and how fast it gets their is the only concern as far as boat performance is concerned or as is tested at our AWSA testing procedures, Hence Our manufactures rely on this testing as a standard even though it is a low standard as per AWSA.

 

These are my findings and are seat of the pants experience as I don't know that any kind of measurement can be made or manufactured to mathematically come up with desired results on a given craft (I could be wrong!). After having run my new 2012 200 and yes with a 450 hp motor and stock propeller I found my self feeling that old Zoom again if I got out of shape or was just not in the game and trying to get it back on the end of the string. Ordered a OJ 13X15.5 4 blade XMP propeller, with the 450 motor I had them put .120 cup in it. Wow what a difference it has made in the feel of the ZO pull. No more zoom and has made the boat feel quite a bit more docile. The hook up off the ball is quite a bit firmer yet it does not want to over react allowing me to keep the ski more in front of me and staying stacked, I can be in better shape to pre turn and keep the line tight. I also feel that the ZO RPM oscillation is minimized. Time are right their at 36 and 34 07-08/94-95 as is the all the buoy times.

I have run this combination on a number of 6 liter 200's and have made the boats feel tremendously better on the skier end and have received many compliment from skiers skiing with this combination.

 

On Saturday I took some photos of the ZO head unit at speed with out a skier (Base line RPM)and was surprised at what I found (not really!) top speed also increased over the stock prop by almost 2 mph.

 

 

Anyway I will be running the OJ combination on this boat for my personal usage. this setup is probably the best skiing Nautique I have ever owned and it has an incredible feel at the end of the string. However as it pulls tournaments it will have the standard "Tested" prop that it came with.

Also, maybe or maybe not but I also dont feel so beat up and tired after a slalom set with this set up, and at my age trying to continue skiing is a chore as it is.

[DW]

Seems like ZO likes a really efficient "torque converter". Great comments, out of curiosity what is the top end on that vessel?

[boarditup]

What you are describing is cavitation providing slippage until pressure shears off the trailing bubbles. It may feel better, but the engineer in me cringes at the thought. CC just went through a lot of prop testing with Acme and the new prop selections for 2012 should provide better ski-ability versus the older selections. The newer props will run at lower rpms, also.

[Jody_Seal]

My only goal with this is to mechanically dampen the harsh over reaction of ZO in Slalom. before ZO and DBW We were able to mechanically dampen or increase response by simply moving the pivot point on the throttle arm of the Carb or throttle body also their were a few gain settings that could be manipulated , before speed control we were setting up our boats to be able to quickly disconnect the secondary's on our carburetors so as to dampen the drivers blocking on throttle control.

In my mind the cavitation/slip in a prop exacerbates the tendency of ZO to over compensate, reduce the slip and the boat will not fall off nor ramp up excessively during the oscillation sequence that the skier provides.

 

DW: Top speed went up nearly 2 MPH, 49.7mph. WOT RPM dropped from 5599 (rev limiter) to 5200. Keep in mind the motor is still in its break in stage has only 13 hours on it. I am looking for some more top end gains once the motor has it's oil change and re-alignment. moving over to synthetic oil and a few adjustments I feel top end RPM and top speed should come up close to 2 more MPH.

 

Want know how much slip is in your propeller? http://www.rbbi.com/folders/prop/propcalc.htm

As per the calculator I went from 0.28% slip to 0.19% . Now running more efficient across the board.

[DooSPX]

Another example of OJ props building their props for the skier not the driver. My OJ XMP 4 blade 13.7x17.5 .110 prop feels light years better behind the boat then the 14x18 3 blade factory prop.

[ForrestGump]

Karl, What do you mean that the new CC prop selections for 2012 will have better skiability? The props are the same as for 2011, at least for the 6.0 and 5.7, from what I've seen rolling into the dealership.

 

 

[EJOJprop]

Jody - Looks Like we hit it pretty close on the first try. Good to see another of our props working well with your CC.

[The_MS]

I would listen to Jody before anyone at CC. Good work Jody.

[eleeski]

A bubbler to add some air onto that prop might get rid of the cavitation induced slipping. The PP classic showed a faster speed with the MC test bubbler - less slippage? It did subjectively improve the feel for the slalom pull.

 

Eric

[swc5150]

Hey Jody,

When you say it makes the 200 a bit more docile, does that also mean the hole shot? The 343 with stock prop has wicked punch out of the hole, and I'm either too light on the throttle (trying to be safe) or just about tearing the arms off my brother. I don't think it's anything time in the boat won't cure, but I'm just curious. I bounce back and forth between my old 190 and the 200, so it's a huge adjustment each time. It also has that zoom effect you speak of, but I assumed that was just the nature of ZO.

 

With 18 hours on it, and an oil pan full of RP, it's up to about 43 @ WOT. Fast enough for the girls we go out with. I just wish the RPMs could be lowered on the small motor.

[Jody_Seal]

Historically the 6 liters do not shine from the hole shot. Have seen this in all three marinizers in all the manufacturers ski boats since the six liters came on the scene. 5.7/350's have been a better hole shot motor however the 6 liters shine the second 60 feet from hole shot and to top end.

In our experiences utilizing the OJ product on the 5.7 is that it has not effected the hole shot but has effected top end speed average a half a MPH less. But the mid range and ski RPM's come down significantly over the stock propellers especially with the 200's. Keep in mind very similar number's can be had on a SB 200 utilizing an ACME 422 or a 654 but these props are not (as is the OJ) AWSA tournament tested on the 200's. Goes back to AWSA's drag race that they seem to believe is comparable to how the boats are utilized in tournament.

 

Again my testing of the OJ products is for my own personal usage and to help me ski better due to the over powering effect that ZO seems to have on me. For me I feel more in tune with the boat and do not have that rushed good god it is going to launch me out the front feeling in my pull phase to the pre turn. confidence is everything in this sport and if I feel confident in my practice then If and when I ski a tournament I will be able to feel confident on the water due to in my mind quality practice.

This set up may not be for every one but I feel for me it works and may help others who are struggling with the ZOOM ZOOM ZOOM OF ZO!

[Weappa]

Great thread Jody - I have an '08 SN with ZeroOff that has got to be the toughest boat I've ever skied behind. I am also running the stock prop that is a bit large for the 5280 altitude in Colorado, so I would suspect some extra slippage due to that. I plan on investigating the prop change to tame this beast. Thanks for the work and sharing it.

[MZito]

@Jody_Seal‌ @EJOJprop‌

Jody the pics above you show rpm's of a 428 on your SN 200 at slalom speeds, is that a 6.0, 5.7 or other? If not a 5.7 are the rpm's roughly the same? I have a '10 SN 200 5.7 with the 1868 and I only slalom and pull my 5yr old around the lake, So I want to re prop. I am 6' and 225 on a ~1800 foot lakes w/ 6 buoys (so I need a decent shot to get to speed). How much will the 428 OJ reduce RPM's from the stock 1868? and as a big guy, will the feel of ZO be better as well? I am looking at 422, 654 and 428. I am liking what I have read so far about the 428 and the success your reporting. Just looking for the the best application for my set up. Eric, if you have some helpful info on this please comment. I appreciate your knowledge you share!

[thager]

Another way to mitigate the zoom is to turn the ZO head more towards parallel with the ski path thus slowing the reaction of the accelerometers. You get the same times but smoother ZO response.

[Jordan]

Cavitation is not a bad thing when it's effects are controlled.

 

Go fast boats and bass boats sometimes use propellers that have vents in the hub which lets exhaust gas bubble out just ahead of each blade to allow rpms to spin up before the prop hooks up. They employ increased rake and cup to handle the cavitation.

 

@eleeski has an interesting idea about introducing air during the hole shot, particularly if it would be on for a short period at the beginning of the hole shot, then turned off.

 

You may be able to get away with higher pitch and more cup with this idea. It would increase top speed and reduce gas consumption.

 

 

[MZito]

the OJ428 is on the 200 (5.7) and will try it out this weekend. Thanks for the recommendation @Jody_Seal‌

 

I hope RPM decrease!

 

 

[animal]

Let us know how the OJ works. I'm looking at a new prop for my boat as well.

[GOODESkier]

@TeamWally‌

[ALPJr]

A few years ago Eric at OJ recommended an OJ XMP 454 for our 92 PS 190. It made an already very nice wake a touch softer, lowered the rpm about 150 at slalom speeds, holds beginner speeds 18 to 22 mph like a Mack truck, and saves fuel. Thanks again Eric !

[DooSPX]

I agree with @ALPJr. I have the same XMP 454 on my 91 and I LOVE it. It does exactly what ALP said and spot on with what Eric told me. Eric is a great guy and I still BS with him on occasion.

[ALPJr]

Oh. I just noticed a typo. RPM's were reduced by 100.

[ALPJr]

Thanks @DooSPX‌

[MZito]

@animal‌ @Jody_Seal‌ @EJOJprop‌ @ejOJprops‌

finally was able to get the sn200 out with the new OJ428 prop. It made a big difference. The hole shot felt the same as the 1868 and the RPM's at 34.2 were 3680-3700 with a 180lbs skier big drop from standard prop~350-400rpms. The wake felt softer. Overall this was well worth the $$$. Hope this helps!

[animal]

Thanks. That's what I was hoping for.