PDA

View Full Version : PowerSlot UpGrade


Ski-A-Rees
09-29-2005, 09:51 AM
I'm repleaceing the 454 in my 89 Mastercraft Prostar 190 and while I'm down and dirty, I've decided to replace the transmission. I was thinking about upgradeing to a PowerSlot and was wondering if the Team Talk Experts could give me there two cents on Pros & Cons! I understand how it works and what it does but would like the know all the Pro's and if there are any Con's! The Boat is used for show skiing so yes it would be worth the cost because it wouldn't be used for regular family fun skiing! Thanks...

Dan K
09-29-2005, 10:52 AM
I have never heard of a con for the power slot, My 81 has one and I believe it provides a more solid pull and torque. A definite plus for show skiing IMO. I am not sure if the not slot hulls can accomodate the larger prop required. I would check into that before you get to far along.

east tx skier
09-29-2005, 10:55 AM
I'm not absolutely sure on this, but the only cons of which I am aware are (1) fuel consumption?, (2) a bit larger prop column in the wake, and (3) a lower top end . With a 454, I don't need to talk to you about fuel consumption. And the prop column for show skiing (if it's noticeably different which is debatable) would be a non-factor.

Ski-A-Rees
09-29-2005, 02:15 PM
My hull has the extra space but never had the trasmission!

chico
09-29-2005, 08:28 PM
you don,t have a slot,the bigger prop would hit.

Hoosier Bob
09-29-2005, 09:07 PM
Just an observation but wouldn't the 454 pretty much offset the need? I also thought the shaft was 1 1/8. If so to handle the prop you would need to change a lot. Shaft, coupler and strut would be too small. If anyone knows for sure it would be nice to know if the 1" shaft can handle a 13/18 prop. :twocents:
I thought also the props were of the same diameter but cupped more (13/18) that being said you could run the prop on a 190.

Ski-A-Rees
09-30-2005, 10:13 AM
In show skiing you need everything you can get for big acts. Such as are Tripple rig Hydrodyne. How bad is the fuel consumption? How much bigger is the wake? The boat is used for pulling barefoot lines. How much does it lower the top end? I may be asking questions people can't answer....

JDK
09-30-2005, 01:22 PM
How much does it lower the top end?

Why do you think the top end would be lowered?

east tx skier
09-30-2005, 02:16 PM
I figured that the max rpms stayed the same. 1.5 revolutions of the motor turns the prop 1 revolution (as opposed to 1:1). Thus, if WOT at 4,600 rpms (4,600 revolutions of the prop) gets you 45 mph on a 1:1, then it gets you 3,067 prop revolutions on a 1.5:1. Now you've got a bigger prop on the powerslot boat, so someone will have to pick up the math for me on the 14x18 versus 13x13 pitch = mph equation. That'd make my head hurt.

I just remember hearing somewhere that you lose a little top end with the lower gear ratio.

Ski-A-Rees
09-30-2005, 04:11 PM
Anyone who had a PowerSlot... What RPM's are you running at barefoot speed? Which engine do you have?

east tx skier
09-30-2005, 04:18 PM
Ah, glad to see I'm not the only one that didn't feel like taking on that little equation. ;)

east tx skier
09-30-2005, 04:29 PM
Okay, my math is really bad. Someone help me. Ski-A-Rees, your question, i.e., someone with a powerslot tell me, is a better idea.

If 1 revolution will push you through the water 18" (14x18 prop). Then 3,067 prop revolutions of the prop per minute (4,600 engine rpms/1.5) will push you 55,206" through the water each minute. That's 3,312,360" per hour. There are 63,360" in a mile. Thus, we're looking, mathmatically (with no other factors considered) at 52 mph. So that would be faster. Now where did I go wrong. ;) Just figured it for the 1:1 running a 13x13 and got 56.5 mph. So obviously, there's some drag that I haven't factored. But theoretically, the pslot will not go as fast at WOT.

Quick, some engineer save this English Major.

ski_king
09-30-2005, 04:46 PM
Mine has the powerslot and the RPM's match the speed almost exactly, 4000 RPM is 40 MPH, 3600 RPM is 36 MPH etc.

According to the numbers, the powerslot should be slower. But there is less slippage with the larger prop and both have about the same top speed.
My top speed is about 46 mph.

ski_king
09-30-2005, 04:48 PM
Doug, your numbers and theory were right on, maybe you should make a career change.

east tx skier
09-30-2005, 04:51 PM
Good to know, but let's not get nuts here on my doing any Goodwill Hunting. ;)

Slippage and diameter. So des neh (sp).

S-A-R, if more torque is what you're after, and as long as you've got the engine out, there are other avenues short of replacing the tranny, that you might explore.

BRAZOS 205
09-30-2005, 04:55 PM
I always used about 17-20% slip in my calculations for my 13x13.
so 56.6 mph x 0.82 = 46+/- mph

east tx skier
09-30-2005, 04:57 PM
Yeah, but don't the 454 boats have huge gas tanks? More weight.

Ski-A-Rees
10-01-2005, 02:20 PM
I don't think my gas tank is any bigger than anyone else of the same model. I could be wrong but thats just my thought.

Dan K
10-01-2005, 02:51 PM
Ski King,
My experience with the slot is the same, Speed matches closely to RPM.
MY 81 tops out around 44-45 with 4500 RPM

H20skeefreek
10-01-2005, 07:04 PM
Yeah, but don't the 454 boats have huge gas tanks? More weight.
on the 80's models, there isn't any more room for a bigger gas tank, just more trips to the station.

SKI*MC
10-01-2005, 09:45 PM
our 83 is a powerslot, the con i can this of with a powerslot is that it has a crap load of turbulance and a huge roostertail. Even at slaloming speeds there is one. But as for the RPM to Speed Ratio, mine is almost identical. its a 1:1 ratio in the trans so i would hope it would be close

crdickey
10-02-2005, 01:01 AM
The slot trans has a lower prop rpm but the prop is much larger so the top end is very close to the same but a bit higher. It was designed when the lower HP motors (250 to 275) would pull down by Pro shortline skiers. The newer high HP boat and Perfect Pass has prompted MC to change from a 1.51:1 ratio down to a 1.26:1 like SN.

There is a slightly larger bump in the slalom wake but not enough to worry about and any shortline skier will be ahead of the bump anyway.

The retro requires a different coupling, shaft, shaft seal, strut, & prop. The strut changes the shaft angle slightly and makes the room needed for the larger prop. There is no difference in the hull of the boat with a factory Powerslot.

The only Con I can see is the expense, but if you're going to do it, ask MC about their new 1.23:1 ratio.

Before you spend any extra money, talk to ACME Marine about a different prop. You may get all you're looking for from a $400.00 prop change instead of a $4,000.00 trans change.

H20skeefreek
10-02-2005, 07:57 AM
The slot trans has a lower prop rpm but the prop is much larger so the top end is very close to the same but a bit higher. It was designed when the lower HP motors (250 to 275) would pull down by Pro shortline skiers. The newer high HP boat and Perfect Pass has prompted MC to change from a 1.51:1 ratio down to a 1.26:1 like SN.

There is a slightly larger bump in the slalom wake but not enough to worry about and any shortline skier will be ahead of the bump anyway.

The retro requires a different coupling, shaft, shaft seal, strut, & prop. The strut changes the shaft angle slightly and makes the room needed for the larger prop. There is no difference in the hull of the boat with a factory Powerslot.

The only Con I can see is the expense, but if you're going to do it, ask MC about their new 1.23:1 ratio.

Before you spend any extra money, talk to ACME Marine about a different prop. You may get all you're looking for from a $400.00 prop change instead of a $4,000.00 trans change.
sorry Crdickey, that is incorrect. the PowerSlot definately has a lower top end speed.

and in some models, the hull was different, but you may be correct that in 1989, there was no difference, but on some hulls there was a difference.

I don't see any reason if he wants more low end torque to ask about the 1.23:1. Buying a new MC transmission would be much more expensive for less gain unless he's going to completely re-power.

I agree on the prop. It may be better to go with a drastically different prop for show skiing than slalom if he is willing to give up more top end.

Cloaked
10-02-2005, 07:59 AM
Ski King,
My experience with the slot is the same, Speed matches closely to RPM.
MY 81 tops out around 44-45 with 4500 RPM :toast: .......

JDK
10-02-2005, 05:12 PM
The slot trans has a lower prop rpm but the prop is much larger so the top end is very close to the same but a bit higher.

Good explanation. This is what I suspected when I asked earlier about the reason for the lower top speed.
Someones going to have to explain WHY the top speed is lower with a slot.

Hoosier Bob
10-02-2005, 07:52 PM
2nd the notion! I recently purchased an Acme 541 for the old 93' and it turned my boat into a rocket. I have both the legend 13x13 three blade and the four blade. Do not discount OJ. I only found the Acme three blade for my boat. I did not find the OJ until after my purchase. That being said my boat responds in so many different areas. Greater holeshot, steady middle and more top end. This is compared to the four and three blade. CNC is the ticket no matter what company you choose. Today I noticed how much more fun cruising is with the kids. I also noticed how much better the boat responds at lower speeds and when pulling the kids on their kneeboards. The boat is faster, quicker and even handles better! Try the prop! :D sorry Crdickey, that is incorrect. the PowerSlot definately has a lower top end speed.

and in some models, the hull was different, but you may be correct that in 1989, there was no difference, but on some hulls there was a difference.

I don't see any reason if he wants more low end torque to ask about the 1.23:1. Buying a new MC transmission would be much more expensive for less gain unless he's going to completely re-power.

I agree on the prop. It may be better to go with a drastically different prop for show skiing than slalom if he is willing to give up more top end.

east tx skier
10-03-2005, 11:59 AM
Hoosier Bob, now that you've got the 541, try swapping intake manifolds. With the GT40, Acme, and new intake, the low end just feels thick as a brick!

Hoosier Bob
10-03-2005, 12:34 PM
Right now the boat is a dream. I still have the original carb setup and it is working perfectly. I may do the manifold swap in the future but for now it will be stock. Did you also upgrade the rockers to 1.5-1? I would love to go manifold and rollers on the upper valve train. I know you have a different carb but were there any other changes other than a manifold swap? Which manifold and is it a direct swap without the need for new cam? May have to add a post to the winter projects!
HoosierHoosier Bob, now that you've got the 541, try swapping intake manifolds. With the GT40, Acme, and new intake, the low end just feels thick as a brick!

east tx skier
10-03-2005, 12:46 PM
Responded in the other thread, too.

Because I don't care about top end, I went with the basic Edelbrock performer manifold from skidim (you can get it other places for less). I didn't mess with anything else as I was not doing the labor myself, but had thought about having the cylinders tweaked for a tad more compression. In the end, decided not to spend the extra $$$. Just had new gaskets put on while they were in there. The boat already had GT40 heads and the Acme 541 on it. Other than the 4160 carb, the prop, and the new intake, it's stock. No need for a new cam, but if you're doing the labor yourself, it's something probably worth adding.

After all was said and done, I was so satisfied that I decided I didn't need a thing more from this engine. One other thing, you'll be amazed how much lighter the Aluminum intake is as opposed to the stock cast iron intake.

Hoosier Bob
10-03-2005, 12:54 PM
Nice points! The new manifold also adds to the aesthetics as well. Edelbrock performer manifolds are available just about everywhere. I am assuming they are the same as the street versions? :dance: I do not think you could ever lose top end with the upgrade. The boost would be in the low to mid probably due to no change in the valve train. No additional fuel being added as well. Add flow, need fuel, work the valves to allow more mixture and increase the fuel supply. Getting expensive. I will go with the manifold! My boat now runs like a rocket at the bottom and the top. The middle seems to be the same. The new prop has even changed the sound of the boat. It seems like it is always in the powerband! Rockets at 35 on and out of the hole.Responded in the other thread, too.

Because I don't care about top end, I went with the basic Edelbrock performer manifold from skidim (you can get it other places for less). I didn't mess with anything else as I was not doing the labor myself, but had thought about having the cylinders tweaked for a tad more compression. In the end, decided not to spend the extra $$$. Just had new gaskets put on while they were in there. The boat already had GT40 heads and the Acme 541 on it. Other than the 4160 carb, the prop, and the new intake, it's stock. No need for a new cam, but if you're doing the labor yourself, it's something probably worth adding.

After all was said and done, I was so satisfied that I decided I didn't need a thing more from this engine. One other thing, you'll be amazed how much lighter the Aluminum intake is as opposed to the stock cast iron intake.

east tx skier
10-03-2005, 02:43 PM
I believe it's the same as the street version. It's all low and mid torque. Gets up to the high revs in an instant.