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jipster43
09-30-2009, 01:27 AM
I apologize for the redundant topic, but here it goes! I know that the Powerslot is stronger out of the hole, but are there any other advantages/disadvantages to the bigger gear? Is the wake affected by the bigger prop/power? Does the 1:1 have a smoother wake? Would a 1993 with the velvet drive ski the course as well as a powerslot? How is fuel consumption by comparison?

It seems most folks prefer the powerslot, but are there some who prefer the velvet drive? If so, why?

Thanks for all yer expertise!

JP :)

JohnE
09-30-2009, 09:15 AM
Biggest advantage to powerslot is out of the hole. Gets you up faster on a short set up and gives you more time to prepare for your pull out.

Wake should be essentially identical.

Both versions should ski essentially identical.

Granted a pro could probably tell the difference but few of us could.

Jim@BAWS
09-30-2009, 09:26 AM
I apologize for the redundant topic, but here it goes! I know that the Powerslot is stronger out of the hole, but are there any other advantages/disadvantages to the bigger gear? Is the wake affected by the bigger prop/power? Does the 1:1 have a smoother wake? Would a 1993 with the velvet drive ski the course as well as a powerslot? How is fuel consumption by comparison?

It seems most folks prefer the powerslot, but are there some who prefer the velvet drive? If so, why?

Thanks for all yer expertise!

JP :)


What Hull and what motor

Jim@BAWS

jipster43
09-30-2009, 02:56 PM
In particular I'm thinking of a 1993 Stars & Stripes with the Ford 351. I keep finding them with velvet drives, but not the powerslot. I can't seem to convince myself that the velvet drive would be sufficient.

I'm beginning to think the '93 S&S never came with the powerslot.

Thanks again!

JP :)

woftam
09-30-2009, 03:03 PM
Unless you are an open class jumper, 38+ off slalom skier, do deep water barefoot starts or pull multiple footers at the same time, the difference should matter little.

Kevin 89MC
09-30-2009, 03:31 PM
I occasionally ski behind a '92 with a 351 and a slot. Granted I'm comparing different hulls, but I actually think the prop hump at 22 off is just a bit bigger than on my '89 direct drive. I have heard that the slot can make the hump a little bigger. It's a pretty small difference, and more often it really depends on how I'm skiing rather than what boat I'm behind.
The '92 is a bit quicker out of the hole than mine, but again not that much. We have a course that has a pretty short setup at one end, and while his is a bit quicker, mine works just fine. Top speeds are about the same I think.
I agree, unless you're dealing with a real short setup, or really need a ton of power out of the hole, either transmission should work plenty fine.
If it were my decision, I'd try to find a way to ski behind both, but I know that can be tough.
Good luck!
Kevin

jipster43
09-30-2009, 03:53 PM
I went back and re-read the recent Stars & Stripes thread.

http://www.mastercraft.com/teamtalk/showthread.php?t=32762&page=2

In it there's an article posted from Waterski Magazine's 1993 Boat Buyer's Guide reviewing the 1993 Stars & Stripes and comparing it to the limited edition with the same engine, but the fuel injection and powerslot transmission. According to this article the velvet drive was marginally slower in acceleration and top speeds, but actually created a better wake and overall slalom ratings. (I had to brake out the magnifying glass to get all that info.)

So, I guess in this particular year, the velvet drive might suit my needs better than the powerslot.

Thanks for all your help guys. I guess the debate will continue according to different hulls and engines.

JP :)

Skipper
09-30-2009, 04:06 PM
When I was shopping for my boat, I asked a similar question. A friend, and life-long MC owner, told me that he loved his power slot but it sucked down more fuel than a 1:1.

EJ OJPROP
09-30-2009, 04:19 PM
Not sure how a PowerSlot trans could suck more fuel......3600 RPM at 36 MPH is 3600 RPM at 36 MPH.....Proped correctly the RPM should be very close to the same with either tranny for a given speed. For many many years we made two sizes of props, 13 X 13 for a 1:1 and a 14 X 18 for a PowerSlot. Both props would turn the same RPM at the same MPH. We did make some 14 X 16's for the big time slalom boys, LaPoint's, because they could slow the Slot down behind the boat and needed higher RPM to maintain times. With a 14 X 16 the RPM would be closer to 4000 for 36 MPH.

Cloaked
09-30-2009, 07:01 PM
I am not following the theory here of a 1:1 vs a 1.51:1, saying that a 1.51:1 is stronger on the low end.

It does have good power coming up but top end is where it will wind out better. The 1:1 has the harder pull (setting aside the HP, ect).

The velvet drive will serve anyone very well, however the companion option very often is the 240 HP vs the 285 HP respectively.

Skipper
09-30-2009, 07:38 PM
Kinda like riding a bicycle up a moderate slope from a complete stop. If the bicycle has only one gear, then it requires a lot of work from the person peddling (the boat engine) to get the bicycle to start moving. If the bicycle had a lower gear then the person peddling could get the bicycle into motion more quickly than one with only one gear.

Of course, as Eric pointed out, the prop on the reduced gear transmission is larger than the 1:1. But the power slot combo gives a noticeably more robust deep water start, especially for a heavier skier.

88 PS190
09-30-2009, 07:56 PM
How would you rate the propeller slip behind a gear reduction equipped transmission vs the 1:1 transmission,

It would seem that a 14X18 would have more "grab" on the water, and less slip than the 13X13 1:1 equipped boats, which would allow a larger engine to more effectively accelerate the boat.

Does that seem to be the case? Afterall the ratio is not the only difference in the boats.

Cloaked
09-30-2009, 07:59 PM
Kinda like riding a bicycle up a moderate slope from a complete stop. If the bicycle has only one gear, then it requires a lot of work from the person peddling (the boat engine) to get the bicycle to start moving. If the bicycle had a lower gear then the person peddling could get the bicycle into motion more quickly than one with only one gear.

Of course, as Eric pointed out, the prop on the reduced gear transmission is larger than the 1:1. But the power slot combo gives a noticeably more robust deep water start, especially for a heavier skier.The prop has no relevance to the functionality of the tranny. Although different prop charastics produce different results, the 1:1 is a lower ratio of pulling power at the bottom end.

That's all I know.

TMCNo1
09-30-2009, 08:35 PM
In particular I'm thinking of a 1993 Stars & Stripes with the Ford 351. I keep finding them with velvet drives, but not the powerslot. I can't seem to convince myself that the velvet drive would be sufficient.

I'm beginning to think the '93 S&S never came with the powerslot.

Thanks again!

JP :)

I'm confused, but here goes,
Until the Hurtz transmissions became standard in the MC lineup, Direct Drive or V-Drive in the last few years, the Borg Warner Velvet Drive transmission was in all MasterCrafts manufactured and available in two versions, 1:1 ratio standard and 1.5:1 ratio Powerslot as a option. IIRC, the '93 ProStars came with one or the other of these transmissions whether it was Ford or Chevy powered. If you have found/or find a '93 Stars and Stripes, it will have a Borg Warner Velvet Drive transmission whether you like it or not, and the ratio can be identified by a tag on top of the transmission.

Skipper
09-30-2009, 09:45 PM
The prop has no relevance to the functionality of the tranny. Although different prop charastics produce different results, the 1:1 is a lower ratio of pulling power at the bottom end.

That's all I know.

The prop is critical to the function of the tranny.

A 1:1 uses a 13" prop.
A 1.23:1 uses a much larger prop.

The larger prop cannot be used on the 1:1 because it will require too much work from the engine. At least it would create a very slow hole shot.

Just the same, the small 13" prop is wrong for the 1.23:1 tranny. This would produce high RPMs with comparatively low thrust.

T-Rager
09-30-2009, 09:50 PM
I have a 1990 ProStar with Ford 351 and 1:1 Velvet Drive. I upgraded the 13 x13 standard OJ prop to an Acme 541 and the difference in the hole shot was remarkable; the top speed remained unchanged. I weigh 200 lbs and the boat rips me out of the water.

Tom

88 PS190
09-30-2009, 10:20 PM
I have a 1990 ProStar with Ford 351 and 1:1 Velvet Drive. I upgraded the 13 x13 standard OJ prop.

Was the prop you had on there the original from 1990? Never repaired/tuned up?

I had ours repaired during the winter because I was getting the aluminum ones from our I/O done and figured why not. And it seemed smoother in the spring, obviously during the winter I may have changed perception, but I do think it helped, the edges were a bit buffed before it went in.

I was talking to a guy who ran a Ski Nautique dealership, and he was commenting about the history of ski boats, through the years. He thought that the 1.5 when it came out did what it needed to with the boats/engines of the day, but that as engines got more powerful 1.25 was closer to ideal. Of course he was also a huge nautique fan, didn't like how MC got rid of the wooden stringers etc. etc.

Cloaked
09-30-2009, 10:29 PM
The prop is critical to the function of the tranny.

A 1:1 uses a 13" prop.
A 1.23:1 uses a much larger prop.

The larger prop cannot be used on the 1:1 because it will require too much work from the engine. At least it would create a very slow hole shot.

Just the same, the small 13" prop is wrong for the 1.23:1 tranny. This would produce high RPMs with comparatively low thrust.The prop is critical only to the output and performance of the boat. The transmission can function with or without a prop. We're talking about ratio and transmission capability, not the results of the propulsion.

(i.e) Driveline in a truck (gears / tranny) is not dependant on functionality with different tires. It works regardless, as is the case with the Velvet drive or the slot.

The larger prop can be used on the 1:1 but the hull does not allow the (larger) prop to be installed unless it has the accommodating powerslot (hull cutout). These things are made for hard work.

T-Rager
09-30-2009, 11:27 PM
Was the prop you had on there the original from 1990? Never repaired/tuned up?

I had ours repaired during the winter because I was getting the aluminum ones from our I/O done and figured why not. And it seemed smoother in the spring, obviously during the winter I may have changed perception, but I do think it helped, the edges were a bit buffed before it went in.

I was talking to a guy who ran a Ski Nautique dealership, and he was commenting about the history of ski boats, through the years. He thought that the 1.5 when it came out did what it needed to with the boats/engines of the day, but that as engines got more powerful 1.25 was closer to ideal. Of course he was also a huge nautique fan, didn't like how MC got rid of the wooden stringers etc. etc.

Yes, the OJ was the original prop. It was (and is) in pristine condition. I've been staring at it here in my office for the last six years.

By the way, as I understand it, the PowerSlot uses a 1.25" diameter drive shaft and the Velvet Drive uses a 1" diameter shaft.

Tom

jipster43
09-30-2009, 11:36 PM
I'm confused, but here goes,
Until the Hurtz transmissions became standard in the MC lineup, Direct Drive or V-Drive in the last few years, the Borg Warner Velvet Drive transmission was in all MasterCrafts manufactured and available in two versions, 1:1 ratio standard and 1.5:1 ratio Powerslot as a option. IIRC, the '93 ProStars came with one or the other of these transmissions whether it was Ford or Chevy powered. If you have found/or find a '93 Stars and Stripes, it will have a Borg Warner Velvet Drive transmission whether you like it or not, and the ratio can be identified by a tag on top of the transmission.

Yeah, I've always heard the transmissions identified as either velvet (1:1) or powerslot (1.5:1) even though they are both technically velvet drives.

JP :)

88 PS190
10-01-2009, 12:51 PM
Yeah, I've always heard the transmissions identified as either velvet (1:1) or powerslot (1.5:1) even though they are both technically velvet drives.

JP :)

Get the Velvet drive service manual and you'll find a ton of variety in ratios, iirc 1 to 3 something.

We have a factory borg warner employee locally who fixes these transmissions, they are in many large boats.

The prop is critical only to the output and performance of the boat. The transmission can function with or without a prop. We're talking about ratio and transmission capability, not the results of the propulsion.

I think that's the important part of the question, as was stated the only difference between a Velvet drive 1:1 and a Velvet drive 1.5:1 is a reduction unit bolted onto the back of the transmission, you can remove the reduction unit.

I think the result of the propulsion therefore is key, 1.5:1 if equipped with a 14X13 prop would go alot of RPM to get anywhere, in the post by OJ Props earlier the comment was that both engines go 3600 rpm at 36 miles per hour approx. One with a 13 pitch, the other with an 18 pitch prop, the steeper pitch prop however is spinning slower than the 13 pitch prop at that same speed.

So the real question is propeller efficiency, I think it would be interesting to calculate prop slip. which is.
pitch x rpm/gear ratio x 1056 = theroretical speed. for the power slot this should be.
18 x 3600 / 1.5 x 1056 which if my phone is right that's 40.91 mph, which in reality is only 36 mph

For the 13 pitch 1:1 the same calculation results in 44.32 mph.

Which means, the 13 pitch prop is slipping far more in the water than the slower spinning 14X18 prop that the power slot can swing. Both boats (according to OJ props) should be going 36 at 3600, but if the props didn't slip the 13x13 would go 44.32 at that rpm.

Thoughts? I think that says to me, at any given rpm the 14x18 is going to 'grip' better, it slips less than the 13x13, which means you give the boat gas and the boat goes. You need the gear reduction to make that happen, if you had a 14x18 on a 1:1 (which you could fit it under the hull since don't they all have the power slot cup in the hull after a certain point in the 80's?) then 18X3600/1056 would go in theory 61.36 if you had the power to swing it.

EJ OJPROP
10-01-2009, 01:28 PM
The numbers seem right, the 1:1 is close to a slip ratio of 19% while the Slot is 12%. The actual slip using the 18 on a 1:1 would be 40%.

88 PS190
10-01-2009, 01:51 PM
thanks for getting back on that, I know the formulas are just estimations as well, and I'm sure there are differences between props for cupping, and if its cast or cnc, in the real world.

Interesting that the actual slip of an 18 on a 1:1 would be so high.

The % comes from
(Theoretical speed - actual speed)/Theoretical speed X 100

So .4 = (61.36-actual)/61.3 Actual speed would be about 37 mph. That's huge loss, and I'd imagine the boat would be easily slowed by a skier.

EJ OJPROP
10-01-2009, 01:55 PM
Lots of factors besides pitch/rpm/mph that are difficult to calculate. Actually should increase the pitch number for propellers that are cupped, at least an inch. Diameter can change the real world numbers but it is not used in most calculations.

88 PS190
10-01-2009, 01:56 PM
But this is close enough to atleast use it as a rough estimate correct?

EJ OJPROP
10-01-2009, 02:18 PM
Rough, yes.

TMCNo1
10-01-2009, 04:14 PM
Yes, the OJ was the original prop. It was (and is) in pristine condition. I've been staring at it here in my office for the last six years.

By the way, as I understand it, the PowerSlot uses a 1.25" diameter drive shaft and the Velvet Drive uses a 1" diameter shaft.

Tom

Velvet Drive PowerSlot transmission with the 1.5:1 ratio uses a 1 1/8" shaft and the Velvet Drive 1:1 ratio uses a 1" shaft.
Who is supplying you with all this amazing info?:confused: