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View Full Version : CNC Wakeboard Prop Upgrade and Top End Speed



Dannad
07-17-2007, 11:58 AM
I have a 2007 Mobius LS which I intended to use for waterskiing more than wakeboarding. We got the CNC Wakeboard Prop Upgrade on the recommendation of the sales guy at the dealership. I am noticing that my top end speed is about 34 mph with two people in the boat and one skiing and significantly less with more passengers. For instance, last night I had 4 people in the boat and 1 skier and I couldn't get the boat over 30mph.
Could this be due to the pitch of the wakeboard prop or is it the boat?
Ideally I would like to be able to ski at 34-36.
Any comments would be appreciated.
Thanks.

JoeTechie
07-17-2007, 12:18 PM
The prop has a LOT to do with this. You should see about 40MPH with that load and the standard CNC prop. The wakeboard prop has much more torque for pulling with fully weighted ballast bags, but loses top end speed in exchange. Your dealer did not ask you the right questions of intended use.

Get the right prop, then use this as a spare, or sell it - lots of people want this prop - you may even be able to trade.


-J

Dannad
07-17-2007, 01:13 PM
Thanks for the reply Joe.
I know that I can't have everything but what are the low end trade offs? Will we still be able to wake surf without much problem?
Thanks.

lowdrag
07-17-2007, 06:18 PM
I can't see why you'd have any problem wakesurfing. You'll lose some holeshot if you've got a lot of ballast and are trying to pull up a boarder, but you're not really doing that with surfing.

gt9118
07-18-2007, 11:22 AM
I will trade you props!

cab13367
07-18-2007, 05:01 PM
I had 4 people in the boat and 1 skier and I couldn't get the boat over 30mph.


What were the rpms at 30 mph? If you are overpropped, you would be at redline. I can't imagine that even with a wakeboard prop, you could not get over 30 mph with 4 people in the boat.

Al

Sled491
07-19-2007, 01:01 AM
Wow that seems really bad, you sure you have the plug in? I'm assuming you have the 325hp? Even so with 8 people in our Outback we can still get over 40MPH. Like was asked before what were the Revs? Was she overheating (maybe you picked up some weeds) check your screen in the cooling lines. Just some ideas

Dannad
07-19-2007, 11:29 AM
The RPM's were just over 4000.
Perhaps there is a more serious issue at hand?

JoeTechie
07-19-2007, 01:13 PM
Outback and LS are VERY different beasts.

LS is longer, wider, deeper, and heavier... all play a part in top speed in water.

OB also has a 3-blade speed prop and a flat bottom hull.

Apples and oranges.

-J

bobwells
07-23-2007, 03:45 PM
you would think if he is running a low pitch prop for more torque/pulling power he would be more on the max end of rpm's... :? if he now goes to a higher pitch for more top end, he will lose even more rpm's...just looks like 4000 aint like pushing too bad, I wouldnt want to run continually at 4k and over but that motor I would think oughta run up to 4800-5200 w/no probs on the top end side... i dont know what pitch props on my boat (mobius/outback '98, it's a 4 blade, turns about 3000K at 32mph. I know weight and size all have bearing but sure looks like his motor aint under pitched if it only turns 4K at WOT. just thinking out loud... :)

hey Joe, by the way I went into Clermont on way home from Tampa yesterday, yall got some beautiful water and land. wake board camp has some awesome beast sitting out front ! looks like big fun :D

Sled491
07-23-2007, 11:34 PM
actually the difference between the OB and the Mobius LS is minimal. The Mobius is 400 lbs heavier but also a foot longer so this offsets (Boyles Law), they have the same draft @ 22inches, and the Mobius is only 1 inch wider. The bow hull profile is similar as well. Not until the two larger Mobius models the XLV and the XLVGG do you see the really big bottom profile changes.

I do agree that the props make a difference but not 10mph just no way.

Get her checked out hopefully its something minor, you no doubt have plenty of warrenty to work with, it's the down time that sucks.

Dannad
07-24-2007, 12:38 PM
I'm taking it for the 20 hour service tomorrow. I hope it's nothing serious.
We do keep the boat in the water and when I took it out yesterday there is a pretty solid layer of algae. I don't suspect that this could slow me down 10 MPH, could it?

JoeTechie
07-24-2007, 02:01 PM
Sled - Boyles law has very little to do with it. Hull speed, wave resistance, and drag are all playing here. The outback is much closer to a planing hull, where the wakeboard hull of the LS is a semi-displacement hull. Thus the ability to make wakes all by itself and the ability of the OB to make almost NONE all by iteself. Simple "draft" comparrisons are useless in ANY hull speed comparrison - I know lots of military ships with 60" drafts that blow away my pram dinghy with 6" draft.

Draft and displacement are not the problem here - and rarely are at speed. Less hull in the water is what changes the equations.

None of this should be a 10MPH change, but it is silly to compare apples to oranges. Compare the LSV to the LS and we are talking. Then it is a simple weight distribution equation. The OB is different from ALL the other boats in the line. Comparing the XLV to the LSV is much closer even with the difference in size.

We are all assuming that the speedo is working correctly as well. It could be an 8MPH difference by prop and a 2MPH offset to the speedo. Very common. Or maybe some other source of drag... With Algae - you could EASILY add 2-5MPH of drag!

-J

bobwells
07-24-2007, 03:35 PM
still wont change fact that changing prop to higher pitch for more speed is
going to lower rpm's more and boat is not turning enuff as is. I may even try to think about a lower pitch prop = more rpms and possible more mph. that engine oughta turn 4800-5200 when maxed out. at this point if everything is firing properly he is running out of h.p. to turn the prop he's got :? I would certainly take it in to dealer or to a motorhead and verify all cyl. are firing and have good compression, check timing and verify throttle is opening all the way. If all of this is par then start playing the prop game. Who knows, the salesman may have propped him wrong from the git go.
that would be the most likely case since the ride is so new. please keep us posted , you got me curious for sure. See if someone will let you try some different props b-4 you buy, when we use to run those screaming out boards we would take numerous props to the lake and try'em all looking for that perfect one that would run us peak rpm's for engine at WOT thereby everything is operating in the "proper power band range"
this wiil give you most efficiency and performance. If you want the big hole shot be prepared for possible over revving at WOT. sorry for all the yappin just been down that road with props, and gears with race cars and boats.

bobwells
07-24-2007, 03:37 PM
BTY, I dont know Sled or Boyle but I've had a few of'em :lol:

bobwells
07-24-2007, 03:44 PM
sleds...not boils... :wink: "whats fun if you cant have it?"

JesseC
07-24-2007, 04:41 PM
We were out in our 02 LSV this weekend and I decided to check my top speed. Two people in the boat, headed down river, tail wind, no chop RPM = 4000, wakeplate down, 4 blade wake prop, 3/4 tank of gas, no gear, and an extremely clean hull......34 MPH on speedo, 34.6 MPH GPS.

bobwells
07-24-2007, 11:34 PM
My son & I went out this afternoon, i took a GPS to ck speedo. at 3k rpm i am running right at 29 mph not 32 as previously stated. bob

Buttafewcoe
07-25-2007, 10:05 AM
I played with some props on my old I/O a few years ago. I was looking for one to give a little better fuel economy and pull the rpm's down a bit @ cruising speed. The original one was a 19 pitch and allowed the engine to turn the rpm's @ WOT as spec'd by the manual. To go to a lower pitch, like a 17 allowed the engine to overrev. She was fast out da hole though!
.
Anyway, I ended up going with a 21 pitch. I lost a few revs at top end but gained 2-3 mph. It accomplished what I set out to do, which was improve fuel economy in the mid-range. The gain was about 15%. I thought that was significant.
.
The stock prop on my 04 OB will let the motor rev to 4800 @ WOT and 45 mph, which is what the manual says. It seems to be the right prop for the set up.
.
When you go switching wheels like that, you are trading something, i.e. top end for pulling (lower pitch), or less revs @ WOT for fuel economy (higher)
.
That's my take on it.
.
B

Buttafewcoe
07-25-2007, 01:40 PM
..... I still think, to minimally affect rpm's @ WOT and top end speed, the 4 blade prop w/ same pitch over the 3 blade will help hole shot.
.
B

Berkut
07-25-2007, 03:00 PM
Some info that may not help.

I recently bought a 'new' '06 XLV to replace my '87 Ski Nautique 2001 (God rest its soul). I love barefooting, skiing, wakeboarding, tubing (I know, that's a bit taboo, but I can't help it),...

I have a 14.25x14.25 (I think) four blade prop. In other words, I have the wakeboarding prop. I also have the fuel injected 350.

My boat tops out at about 41 mph (four people, some ballast, towing nobody) at about 5200rpm. My old boat topped out at 45 mph at about 4400rpm (WOT for that engine), so I was concerned about the footing.

So far so good! When my wife and I go for a run I'm told we are running about 38 mph. I'm guessing we're actually going a little faster based on the feel of the water, but it's hard to see the speedo when you're 100ft away! In case it matters, I weigh in at 225lbs and my wife is much, much lower (some info just isn't public knowledge :D ).

Hole shot has also not been an issue. We usually start slalom and I've never thought, "Wow, this is taking a long time."

If it matters, on the Nautique, I tried 13x12 (diameter x pitch), 13x13, and 13x14 three blade props before settling on a 13x14 four blade prop. It had better hole shot than the 13x13 and better top end speed than the 13x14. The 13x12 was not in the best shape so I couldn't tell you how the 13x13 four blade compared to it.

Buttafewcoe
07-26-2007, 07:43 AM
One thing we haven't mentioned is the effect of changing diameters of the prop. A larger diameter will net more surface area giving a better bite improving hole shot also.
.
B

Dannad
07-26-2007, 02:38 PM
I took the boat out with the dealer last night and tried a few different props out. They didn't have anything in stock that could get the RPMs above 4300 and the boat above 37 MPH. They are going to call OJ today.
Has anyone else got the CNC wakeboard prop upgrade and if so how many blades does it have?

MasterMind3002
07-26-2007, 04:07 PM
My 07 Outback with the 325HP engine running the stock factory 3 blade prop tops out at around 45-46 MPH. I was considering going to a 4 blade CNC prop but was told to expect much slower WOT and like others that have posted here I was concerned about barefooting. Has anyone here installed the 4 blade prop on their Outback and if so, how much top end speed did you lose??

Dannad
07-26-2007, 08:05 PM
I just spoke with the dealer who said that OJ is sending a 13X11.5. From what I can tell in the reviews that is the stock prop that the boat would have come with if I didn't select the wakeboard upgrade.
Does anyone know the dimensions of the "Prop, CNC wakeboard upgrade"?
Thanks.

Sled491
07-27-2007, 12:56 PM
Matermind, my buddy just put a 13x13 4 blade on his 06 outback. Very nice out of the hole, holds speed better in the turns and lost about 2-3 MPH on WOT, not bad considering.

Joe went to my dealer on tuesday to drop my boat off and went in to ask the questions that we are debating here. I was told that the outback LS and the Modius LS are basically the same boat or if you prefer hull profile. I'm not saying that we are comparing apples to apples, but there are enough similarities to draw some conclusions, nothing else.

Dannad
07-27-2007, 02:15 PM
Sled,
I think that Joe was referring to the Outback not the Outback LS. The Mobius LS and Outback LS are the same boat but the Mobius comes stock with wakeboard tower. The Outback on the other hand is shorter, lighter with a flatter hull. More of a ski boat than a cross-over.
Anyway, I use my boat at about 3,900 feet. Is there a calculation to see how much that will affect the RPM's?
Thanks for everyones input.

JoeTechie
07-27-2007, 04:00 PM
Sled -

Dannad has it exactly.

ALL of the "LS" series are the EXACT same hull.

Outback LS, Outback LSV, Mobius LS, Mobius LSV.

The "Outback" is a smaller, narrower, lighter, lower freeboard, flat bottom boat.

I was arguing the Base Outback hull (and setup, since it uses a 3-blade speed prop that NO other model uses either), vs an LS hull (which is a stepped rear convex wakeboard hull with a 4 blade prop and ....) etc.

And I was simply negating your comparrison when we were discussing something else regarding the LS hull, so your comparrison to your OB Base hull and speeds are NOT relavant - Apples and Oranges.

:)

Sorry if there was confusion there.

-J

JesseC
07-27-2007, 06:15 PM
Does anybody know what the LS stands for. The V is obvious, but does the LS stand for anyting or is it just a model representation? I have always been curious...

Dannad
07-27-2007, 06:35 PM
Joe,
My Mobius LS came with a 3 Blade Prop. Again I don't understand this because I ordered the Wakeboard Prop Upgrade and would have assumed that it would be a 4 blade.

JoeTechie
07-27-2007, 09:45 PM
My Mobius LS came with a 3 Blade Prop.


:shock: :( :?:



I ordered the Wakeboard Prop Upgrade

:shock: :shock: :shock: :evil: :evil: :!:

I think your dealer has his hand in Lindsey Lohan's pocket.

-J

Berkut
08-02-2007, 01:23 PM
Check this out:
http://www.skidim.com/Faq_Prop.asp

I've been doing business with Discount Inboard Marine for years now and have not had a single problem with them. They are VERY knowledgable and helpful when I've had problems or simply when I don't know exactly what part I need for my boat.

It seems they have a 30 day return policy on undamaged props. That is amazing to me...you get to buy the prop, try it, and if you don't like its performance ship it back to them.

By the way, I have the wakeboard prop on my boat and it is a 4 blade.

Just my 1.5 cents...

JesseC
08-02-2007, 02:31 PM
I got an email from skidim that contained the following:

Enter the promotional code word
SUMMER
at checkout for 10% off entire order in addition to just reduced sales prices on ACME props.

Hurry! This offer is ONLY good through August 31st, 2007!

All ACME Props Reduced For CLEARANCE!

Berkut
08-02-2007, 03:57 PM
I too have been doing some prop research and here is what I've found.

My current prop (14.5x14.25 4-blade 'wakeboard' prop) tops out at 40mph. I was told this prop lives up to its name...it's a wakeboard prop. It is meant for a heavily weighted boat pulling a wakeboarder up to 25mph. It has the best hole shot and the best fuel efficiency when used in that capacity.

However, for those of us who want to ski and barefoot as well as wakeboard, a better choice MAY be the 13.7x17.5 4-blade prop (item #2033 on skidim.com). It ought give two or three mile an hour at the top end along with lowering the rpm at WOT by a few hundred.

When the money becomes available (currently this prop, with basic shipping, is about $408), I will get the 'all around' prop and give it a whirl.

Just a reminder, I have an '06 Mobius XLV.