Sporty vs JC at 110+++

Npark

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Hey guys would love to get some ideas and opinions on the different lift characterists of the two cases at speed.

I have a 2002t I bought from Brack that has been running really good with my lightly warmed up 15" 280 and stock skegged sporty (1.87) combo. I have the 8200rpm race box and I have taken some small props to 8300-8400. Not 100% sure where the limiter finally kicks in, maybe someone can chime in on that too. I'm thinking it's 8350-8400.

Currently running 12" back on a Ally plate and 1" over pad. Boat is super stable and I've been able to push a worked 15x30 Performer SC 3 to 81-8200. Water pressure is still 22+ at speed and slips have been in the 8% range. I figure they should come down on a longer run were I can ease into slower.

Trae Appling is currently building me a JC case and I should have it soon. Question is how will the JC act as compared to the sporty? More/less bow lift, more/less stern? In general do you guys run them higher or lower than a sporty? How do they like the big diameter wheels? The sporty seems to like it but I have to get the engine up there!!

Thanks in advance for the info

Nate
 
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Dave Hensley

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110 mph is a lot of speed for a stock Sportmaster. I have heard of it being done with big diameter props and 1.5" above pad and running out of water pressure in order to hide that big gearcase. You didn't mention what the "JC" case started life as so hard to predict what you might see in performance difference.
 

Dave Hensley

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Smaller case. Thinner skeg. Less stern lift. Probably can run the motor lower and not lose speed. Stern lift will get you in trouble quick in an XB2002 that has a healthy pencil roll. Especially with big props. Better be sure to have a good jacket with rib protection, helmet with restraints and your kill switch hooked up at the speeds you mention. Lots of room to get thrown around in an XB2002 and the gunnels hurt when they hit your ribs/head. I know.
 

Npark

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Ok thanks, less stern lift is intereting. She's running really flat right now. There has been some light work on the pad but most of the pencil roll is still there especially on the outer most portion of the pad.

Yes sir, Lifeline is always on with the kill switch. I do need to start wearing my helmet for these runs.

So in theory, a coned 200 case could still run a big diameter (ET style) prop that makes good stern lift? It would just be lower in the water?

Please don't take this the wrong way (I'm just trying to make sure I fully understand the dynamics at work here) but if a JC coned 200 case builds less stern lift would you not want to run it higher so that the boat is flatter? Everytime we have pushed the setback out an inch and gone up a 1/4 on prop height the boat has gotten flatter.
 

Dave Hensley

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Flatter is relative. It's how much wetted surface the boat is running on. The way I think about it is the smaller the case the lower you can run it without increasing the stern lift and maintain water pressure. I am not a big fan of lots of set back on an unloaded xb2002. Set back is used as a crutch for carrying a load. It is just a lever. I personally like 9-1/2 to 10" set back with 280+ hp. Don probably had it set up to carry a fishing load. Don't wear a full face helmet without restraints or they will pick your helmet up with your head still in it. Sounds like you are in pretty rare air with the speeds you are reporting. Shook might reveal some of his set up numbers. He has been as fast as anyone I know in an XB2002. There are so many variables at work with driver, prop, lip, set back, gearcase profile etc the only thing you can do is keep trying until you get wet and then back up a little....
 

Npark

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Flatter is relative. It's how much wetted surface the boat is running on. The way I think about it is the smaller the case the lower you can run it without increasing the stern lift and maintain water pressure.

There are so many variables at work with driver, prop, lip, set back, gearcase profile etc the only thing you can do is keep trying until you get wet and then back up a little....
Thanks for the clarification on flatter. So you are saying with the smaller cases you run deeper WITHOUT building (excessive) stern lift? And as I go up on the I am going to be building more and more stern lift? I guess the question now is, with my current setup/sporty why would another 1/8th or 1/4 on top of the 1" over generate any more stern lift? Of course I don't want to get to that point that I have too much and around she goes just curious if the bullet is already on top of the surface how another .25 will change it.

I'm definitely not arguing anything so please don't misunderstand me, just trying to grasp the concept.
 
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gmorgan

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Thanks for the clarification on flatter. So you are saying with the smaller cases you run deeper WITHOUT building (excessive) stern lift? And as I go up on the I am going to be building more and more stern lift? I guess the question now is, with my current setup/sporty why would another 1/8th or 1/4 on top of the 1" over generate any more stern lift? Of course I don't want to get to that point that I have too much and around she goes just curious if the bullet is already on top of the surface how another .25 will change it.

I'm definitely not arguing anything so please don't misunderstand me, just trying to grasp the concept.
You are already at the point where you can go around and around with the type gearcase you are running. The best thing you could do is build an XR6 gearcase as bulletproof as you can, and it will improve everything, including handling, safety and speed.
 

Npark

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Thanks for the info gmorgan. The larger sporty skeg doesn't help keep it planted? It's been super stable so far.

Not to veer too far off track, however. Coned 200 case or even an XR6 = lower prop to pad from the sounds of it. Prolly a smaller prop to turn too because I can't turn this prop unless it's high.
 

Dave Hensley

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Raising the transom height of the motor shouldn't increase stern lift with any case in my opinion. I said the smaller the case the lower you should be able to run it without increasing stern lift with everything else remaining the same. Just trying to keep you from getting hurt. An XB2002 doesn't give much warning and running flat gives no time to lessen the violence of hooking one when the prop blows out. There are several folks out there who have ran really fast with worked Sportmasters. Not saying it can't be done. Just wouldn't be my first choice.
 

Npark

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Ok I know understand what you were saying. Sometimes (for me at least) I can lose stuff in translation via the back and forth text/type.

I def agree that there is little margin for error especially when running flat. I know my lake props carry the bow much more so I can navigate wakes better and not worry so much about bow steering.

I spoke to Tim at Hoss at length the other day and he's building me a prop that should be money for one of my coned cases. Basically a Jasper setup :)
 

gmorgan

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Your mileage may vary on the use of an xr6 gearcase. I know it has to be less durable than a bigger case, but the ones I used in drag racing and top end running never failed me. I did not use a reverse gear and always cranked in gear. My gearcase man has been building them for almost 45 years, so he may have done some things I'm unaware of. JC did the torque tab and nosecone.
 

Npark

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My home lake is far too rough to run an XR6 and my hull is heavy at 920# before full sized batteries. Maybe for a top speed only case but it hard for me to justify a case for that purpose only. Plus the Geigertech stuff in unobtainable right now :-/.

Gonna try this JC case and see how it responds as compared to my sporty.

On a tangent, when you go back 1" in setback how much does the transom angle push the motor down?
 

JCSmile

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I believe every inch back is down an 1/8 but hopefully someone will confirm.
 

Dave Hensley

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You have to measure the compounded transom angle with the jackplate included. After that it is simple geometry. It will be the degrees of movement along the radius of the curve converted to change in height in inches.
 

Npark

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You have to measure the compounded transom angle with the jackplate included. After that it is simple geometry. It will be the degrees of movement along the radius of the curve converted to change in height in inches.
Wonderful, thanks for all the info!!
 
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