Zero Off and Reconditioned Propellers

[MARK-S]

I think it would be worth testing a 3 blade but I dont know anything about that stuff as it relates to the trany.

[Fast351]

Zero off does not sample "100s of times per second" unless they've switched antennas. They use a garmin antenna (or at least they did in 2008 when they came out) specifically this one, which updates 5x/second. 5x a second is still plenty fast for what they're trying to do btw.

https://buy.garmin.com/shop/shop.do?cID=158&pID=13195

ETA: http://zerogps.com/product_info.php?...roducts_id=275

[scoke]

Shipped off one of my 422 props to a local high-end prop guy today via USPS. He's supposed to call me this week and take a look at it; but the point is to check the cup(if possible) and re-cup it to meet the 0.105 and if it can be bumped to .1x+ maybe go with it. The 668 cup is .150 so there's a bit of difference.

We were turning up to 3965+ rpms at 36 while Jfox was loading the rope here and there. Not sure what rpms I was bouncing out of but either way, the ZO on that prop has no give thereby feeling like a freight train on the skier.

One of the theories, we feel solid on, is when you are that high in the rpm range-powerband-torque curves, ZO is making it's sampling per split seconds, the boat has no "give" to it.

We did put another 422 back on it. It was a refurbed one as well that we haven't skied since April of last year. We might have the same issue or it might feel sweet and slow like that black/blue boat out of Southern Canada does.

scoke.

[teamseal]

Hi,
A couple of things to consider and point out. Zero Off does not operate solely off of a GPS speed signal, There are three accelerometers built into the head unit. During control function there are many things that contribute to a bad feel to the skier. A skier that hits hard and causes a oscillation in the forward mass movement of the boat has a impact on these accelerometers and the response from the system is to comply with the demand.
Choppy water, rollers prior to the course even wind conditions have impact on mass oscillation in accordance to what the skier and boat are doing.
Damaged and higher slipping propellers will enhance the boats tendency for Higher mass oscillation when pulling a skier.
Some time while driving the boat (with out a skier) with the system engaged reach up and tap on the dash next to the ZO head unit and see what happens..

I have 09 196 with a 6 liter, We use it for tournaments at Cory’s in SRB. In fact Regina set her world overall record behind it. The big thing with this boat is that with ANY Acme on it is an ok feeling slalom boat, however as soon as it we get it back to the shop we pull the ACME off and install A OJ for general use and practice. Night and day difference. Rpm’s at slalom speeds drop 40 rpm and the boat has a whole nicer softer feel.
My son prefers to jump with the OJ on as he feels it develops better acceleration and stabilizes better in the counter cut.

[scoke]

Spoke with prop guy Monday afternoon. He was looking at it and immediately said "whoa, this prop has very little to no cup on it."

He went on to describe Acme propellers as being very thin on their original CNC cutting and then when they are re-worked, it's hard for the machine to re-cup the prop. Almost to the point of it being needed to be finished by hand. We talked about the 0.105 or better but he thought we had more in the .000 range on the prop! Same prop most guys felt our boat was a freight train. He's supposed to work his magic on it tomorrow so I'll give him a call Friday and see what he thinks.

He has a pretty strong resume':Glen has accumulated over 21 years of experience in the Hi-Performance Marine Industry and is certified by the National Marine Propeller Association as a Hi-Performance Propeller Technician. Glen continues now to supply the marine industry today with record-setting national and world champion propeller designs

Hurry up and warm out so we can test some props!!

[TRST]

I would be interested to hear more feedback/comparison on the OJ prop. Teamseal which OJ do you use?

[scoke]

The prop came back into my hands. Very interesting comments once he put it on the bench and started working it.

The prop not only had "NO CUP" but had negative cup. it's supposed to be 0.105 but he felt is more in the -0.1 range.

He had a couple of theories regarding the cup: Acme props are already very thin. The prop was re-worked and the cup wasn't set properly. Then we have skied 250+hours on this prop since March, mostly at 36mph. Flat out could have tweaked the tips as we skied. Also, one minor bump on something at low speeds could have done it.

Either way, it was $148 to have it correctly setup. We plan on pulling the other prop(reworked this summer but not run) off the boat and putting calipers to both of them.

Theory: As long as the prop is out of tolerance, ZO is going to work much harder as the prop is slipping in the water. The skier is going to feel it and one mistake they are going to feel like the boat is all over them.

[scoke]

update!

So we receivedthe re-worked prop (after finding it had a negative cup) into our hands but didn't actually put it on. We had another 422 prop that had been reworked previously but was ready to go.

We skied the new vs old prop. HOLY SMOKES.

When people start talking about boat to boat differences, it's rarely the actual engine, might be the hull but most likely it's the prop.

Previous prop had zero vibrations, felt very smooth but like a freight train to all ranges of skiers.
We were running 3910-3990 and an occasional 4000 rpms while pulling a skier through 28-32off for 36.

With new prop yesterday, we were turning 3780ish, saw some 3810's and a 3850.

The boat felt AMAZING different. Almost like a new/different boat. The rooster tail was in a hair of a different spot as well as the wake felt smoother with only just a driver vs we used to have to load 140+lbs in it.

This situation is similar to the SN 200, turning too many RPMs puts the boat/skier into a higher torque curve and almost punishes the skier. Allegedly they are working on a completely different prop for the boat. But that's for another post as this thread is about ZO and reworked props!

[scoke]

Well we put a hand cupped prop onto the boat.

Amazing...

At 36mph with a 185lb passenger, 195lb driver and 195lb skier, we are only turning 3650 rpms through the entrance gates and saw only 3700 max load with the skier.

Boat feels much better!

Conclusion, the prop is crucial on any boat but even more so wtih Zero Off.

[MARK-S]

Scoke

See you on May 20 for a re-ride