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Power Slot "Type" of Mod

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The question I have is, is it possible to buy a Power Slot type of modification for the Malibus? I was pulled by a 1988 MC ProStar last summer. I have never in my skiing life been yanked out of the water that fast.

Any leads would be appreciated.

Joe

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chathamsolutions

J.

Can you elaborate for us non-gear heads? :)

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WakeGirl

On the Mastercrafts, the Powerslot is an option that is comprised of a transmission that turns 1 rotation for every one and a half rotations of the engine, a larger prop shaft (1 1/8 inches in diameter instead of 1 inch, although our Malibus already have that 1 1/8 inch shaft) a larger propeller (14 inch instead of 13 inch (different pitch too)) and originally, a concave area in the back of the hull to accomodate the bigger propeller.(the Slot) In English, it is a gear reduced transmission 1.5:1 ratio, instead of a standard 1:1 transmission, designed to give you more low end torque and pulling power out of the hole.

On the smaller ski boats, hole shot isn't normally a huge deal. But on the bigger DD boats power to weight becomes an issue & a design like this could really help, especially if you're running into issues like elevation's effect on power, a particularly big person behind the boat, etc. Seems like I saw info on this a while back & maybe it was Ski-Dim that had the parts & know-how, but my memory's failing me tonight & I can't be sure. :unsure: (I do know that Malibu's v-drives come with a reduced gear ratio tranny, but I'm not sure about the big 23' foot DD XTIs. Looking at the prop that comes on them, I'm guessing no.)

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Slider

My dad is installing a gear reduction in his hot rod. This part only adds 5" to the over all length of the transmission. It doesn't affect the current gearing except to add a low gear. (the other gears remain the same)

If I could find something like that for a boat (aside from buying a 2 speed MB) it would be just perfect.

Joe

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UWSkier

I seem to remember reading about someone doing this a couple years ago...

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Kellyb

Where is TR when you need him?

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SacRiverRat

How does the gear reduction help with the holeshot?.. My gear head is confused... either way, don't you just compensate for the RPM range with the appropiate pitch on the prop?

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UWSkier
How does the gear reduction help with the holeshot?.. My gear head is confused... either way, don't you just compensate for the RPM range with the appropiate pitch on the prop?

Sortof. The properties of hydrodynamics don't necessarily make it a 1:1 ratio when compensating for the lack of gear drives.

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SmoothWaterMan

Gear reduction is all about putting torque into the water, and getting the boat to "hook up", in car talk.

By gearing the tranny down 1.5:1, you are essentially driving the car in 2nd gear instead of 4th gear. It has lots more torque by the fact that it's geared down. Naturally with the same size tires (prop in our case), the power will just smoke 'em. So, you need to go up in prop size to harness the power. But, you haven't lessened the power, you've just harnessed it.....allowing it to hook up right NOW. :) :) :) :)

Power is pointless. Torque is all we need.

pb.

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SmoothWaterMan

ps - Just swap out the tranny - you can buy a 1.5:1 and drop it in place of your 1.1:1.

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aneal000

Why would someone want to change over the transmission when you could easily go to a lower pitch prop and achieve the same level of acceleration or "get up on plane"? I realize the bigger prop will "bite" better, cause the boat to hook up better, etc... but man I don't see this as a worth while swap. I've spent quite a bit of time in a Prostar 190 with the power slot and while it got up on plane quick, I don't think it was much more, if any more impressive than say a RLXi with the monsoon... IMHO. The MC has a very low top speed, it was around 44mph, so it is a trade off, just like going to a lower pitch prop.

I'm sure I'm missing the concept of "hooking up"... cause this seems like 95% marketing here... I mean, come on.... MC has everyone calling a transmission a "Power Solt" for xxx'x sake!

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SacRiverRat

That's what I'm thinking - bigger prop may help with some efficiency, but it will still come down to the pictch for that low end hole shot - and it comes at a top end cost

Educate me here... seems the only way to do more work in less time is to have more power.

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UWSkier

More prop in the water = more holeshot but lower top speed if pitch is equal. This is due to the added drag a larger prop must overcome.

Gear redux boats can run a larger, higher-pitched prop without lugging the motor down at low RPM. Once the boat is on plane, the advantage to the gear redux is essentially gone. At these speeds, the non-reduxed boat is in its powerband and should accelerate right with a comparably powered reduxed boat.

As an aside, low-propped, reduxed boats suck fuel like crazy. My primary slalom tow rig when in the course is an SN206. At 36 MPH, that thing is turning insane RPM. Our VLX (also reduxed, but propped to feel like a normal Malibu) just chugs along at that speed.

It shouldn't be deduced that all boats with a gear reduction are slow however. In 2001, the Sunsetter VLX hit 51 MPH in the WSM tests. It was the fastest inboard tested.

Edited by UWSkier

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WakeGirl

Wow that's a fast v-drive.

Peter, is that you?

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SacRiverRat

51?? crap - guess that is w/o tower, and down hill Dontknow.gif

... I think I'm hittin about 45 tops (GPS), but the LSV is bigger, have that big tower thing sticking up (weight and drag) - and I prop'd down so I could get some decent hole shot when loaded

Though I think that was about the top speed before I changed the prop too. Maybe I need to pull the engine from the Pimpala again and do some testing in the boat Rockon.gif

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SacRiverRat

<----- Looking over a my picture, I guess it become aparent why I can't do 51 ;)

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WakeGirl

I think the boat that Matt's talking about is on the Diamond Hull, that would account for some of it.

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SacRiverRat

Speaking of Diamond hull - seems like lots of people quote different things about the wake hull vs diamond hull (I think you are right Tracie)

Do we have the "facts" as to what years/models had what? - might be nice to have that documened somewhere in a forum so we could tell people to search for it Yes.gif

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WakeGirl

We have a chart that goes through 2005 that we'll get up when we get the tech article section up & running.

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SacRiverRat
:salute: atta girl!

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aneal000
More prop in the water = more holeshot but lower top speed if pitch is equal.  This is due to the added drag a larger prop must overcome.

Gear redux boats can run a larger, higher-pitched prop without lugging the motor down at low RPM.  Once the boat is on plane, the advantage to the gear redux is essentially gone.

Don't take this the wrong way, but I'm not buying it. It sounds more like double talk.

Your comments don't make sense. Example a standard DD with 340HP motor runs a 1:1 tranny with a 13x13 prop. A similar boat with a 1.5:1 tranny has to run a 14x18 prop because it is spinning at 1/3 less the rotational speed. I say "has to", when it is actually "in reality" or "that's what Malibu does." The prop's pitch is made up of two numbers, the first is a diameter, 13", 14" diameter. The second is pitch, or # of inches of forward movement for each rotation. You spin it 1 time and it moves forward 13" or 18", respectively. The pitch is directly related to the diameter, you can't change the diameter without affecting the pitch.

The car transmission and tire example is interesting and my take on it is more like this: You just put a lower gear in your car so you expect it to accelerate quicker and lose top speed, which makes sense so far. That's what would happen if you swapped out the 1:1 with a 1:1.5. But that's not what is happening (at least in MC case). They swap out transmissions (back to car example again) and put on taller (larger diameter) tires (equalivent to a larger diameter and pitch prop). The net result cancels each other out, your back to where you started.

If you consider a prop to be 100% efficient you can calculate the following:

you spin a 13x13 at 2K (in a 1:1) you move forward 26K" or 2166' per min

you spin a 14x18 at 2K (in a 1:1.5) you move forward 24K" or 2000' per min

Taking this known number if you take your 1:1 equipped boat and run a lower pitch you can achieve the same forward movement, example:

you spin a 13x12 at 2K (in a 1:1) you move forward 24K" or 2000' per min

The pitch of the prop is designed/calculate to allow the motor to operate efficiently up to the physical limits (rev limiter) of the motor.

In this example (specifically 1:1 to 1:1.5) I don't see where one is far better than the other. Change your current pitch prop and see if you don't get the performance gains you are looking for on the low end.

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whiteVLX
51?? crap - guess that is w/o tower, and down hill  Dontknow.gif

... I think I'm hittin about 45 tops (GPS), but the LSV is bigger, have that big tower thing sticking up (weight and drag) - and I prop'd down so I could get some decent hole shot when loaded

Though I think that was about the top speed before I changed the prop too.  Maybe I need to pull the engine from the Pimpala again and do some testing in the boat  Rockon.gif

47-48 for my 2001 VLX but that's running 89 and me alone in the boat.

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whiteVLX

I forgot to add you can always drop your pitch to increase hole shot but at the sacrifice of top end speed. It's a great way to fix things up if you run a heavy voat.

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SmoothWaterMan

The math on paper only accounts for power and speed. The drag induced during use, and the percent of change between tranny and prop size respectively, is the true answer.

A farmer's son (like myself) at Malibu installed a 1.5:1 in a Response. It flew. He wanted to use it. Bob Alkema said no. End of story.

Non-Diamond hulls are faster than diamond hulls.

A properly equipped 21 LSV is FAST. Fast of the hole, Fast top end. It will stay with a Response. End of story.

pb. :)

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Slider

Can you buy a 1.5:1 tranny that will fit stock in a WS DD? If so any ideas on cost. I just know that a power slot MC explodes out of the hole and still runs mid 40s on the top end. Same hull as our old MB, which had a 1:1 tranny was slower out of the hole, same top end and had a much higher HP rated engine.

Joe

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