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Hard Core Member
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406 Posts
Discussion Starter #1
I'm going to run my TR2 at the races this summer, with the blown 540 that was in my hydro. I'm going to shoot for the 9.0 bracket which shouldn't pose any problem. Question is, what would be a good gear to run? With a mild 454, I could top out a set of 25's at 94 mph although I don't know if I could have run that in a 1/4 mile. The 540 took my hydro to 141 mph through the lights at 7800 rpm. With that motor in a runner bottom, would 29's or 32's be about right? I would want to keep the rpm's around 7400.
DJ
 
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1,011 Posts
Hey Jim. Getting back into racing again? Are you going to run SLDBA or just the Michigan stuff? This economy has my budget about shot. Only thing I'm going to run as it stands now is High Point. Maybe we can mix it up there if you come seeing you're looking to run the 9's. Hope to see ya.

Tim
 

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Hard Core Member
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406 Posts
Discussion Starter #8
Hey Jim. Getting back into racing again? Are you going to run SLDBA or just the Michigan stuff? This economy has my budget about shot. Only thing I'm going to run as it stands now is High Point. Maybe we can mix it up there if you come seeing you're looking to run the 9's. Hope to see ya.

Tim
Well, I have a lot of obstacles to get past but I might make it to St. Louis. High Point is looking good also. Money's tight around here so no points chase for me.
DJ
 

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Hard Core Member
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406 Posts
Discussion Starter #11
It has 25's in it right now and it is at 6500 rpm or so at 94 mph. Seems like I have a lot of slippage. I would guess that the big motor would run 110 or 115 in the 1/4 mile, just don't want to keep spinning it to 7600.
 

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just a ski boat with bark
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It has 25's in it right now and it is at 6500 rpm or so at 94 mph. Seems like I have a lot of slippage. I would guess that the big motor would run 110 or 115 in the 1/4 mile, just don't want to keep spinning it to 7600.
Yes 94mph at 6500rpm with 1.25% gears and an 11x16 prop comes out to be 23.6% slip. Is the boat wet like this? Will it free up with the extra propshaft rpm and additional mph?

7400rpm with 25's would be about 112mph with 20% slip. I don't know anything about your boat combination but it does seem to have more slippage than most.
 

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QUICKIE
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75 Posts
32s will make it fly

I have a Hondo with 32% o.d. BLOWN GAS it pulls that ratio just fine
7000 -8000 11 1/2 17 prop. 120 + g.p.s. when i get the balls to :|errk
it. 1140 h.p. on the dino.
 

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Distinguished Member
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5,775 Posts
It has 25's in it right now and it is at 6500 rpm or so at 94 mph. Seems like I have a lot of slippage. I would guess that the big motor would run 110 or 115 in the 1/4 mile, just don't want to keep spinning it to 7600.
DJ, you'll get a lot of opinions and here's another. Seems to be a lot of variation in the 11x16 Menkins but most work pretty good. With that prop and with what you say about your motor, I'd try 29's. A lot of guys now a days are using small gears successfully.... I'm not one of them. Small gears seem to work best in light boats with engines that RPM fairly high. I know the PGF guys like 12's or 15's and run over 140 MPH, but at over 9k RPM!!
In our old Kurtis, we ran an 11x16 Menkins with 29's and ran consistantly in the mid-high 120's @ 8k RPM with about the same HP. The same prop/motor in our first Canyon only needed 25's to go low 130's.
Bigger motors generally make more torque at lower RPM. Our 588 NA motor made all it's HP below 7200 RPM. We never got that combo completely sorted out before switching to blown alcohol but it liked a big gear as well.
Good luck
 

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adjones419
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1,064 Posts
I agree with David, meaning I'd start with 29's in it. That Menkens 11 x 16 is a great prop, same thing I run on my Mako. With a blower in a flat, whether it be on gas or alcohol, I don't see why anyone would run less than 29's. You might even end up using 32's. Better have both of them in the race trailer, or know someone at the track that has an extra set waiting for you to try.

Screw it. I'll underdrive my blower and throw some weights in the boat to come play in the 9's with you.
 

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Hard Core Member
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406 Posts
Discussion Starter #17
I agree with David, meaning I'd start with 29's in it. That Menkens 11 x 16 is a great prop, same thing I run on my Mako. With a blower in a flat, whether it be on gas or alcohol, I don't see why anyone would run less than 29's. You might even end up using 32's. Better have both of them in the race trailer, or know someone at the track that has an extra set waiting for you to try.

Screw it. I'll underdrive my blower and throw some weights in the boat to come play in the 9's with you.
Hah, I sold all my lower gears when I was running the hydro. I have 40's and up. I'll show up with the 25's in it and see what happens.
 

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Speedy Member
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6,785 Posts
Just a blown gas deal, 8-71 no teflon, maybe 700 - 800 horsepower?
700-800 hp is the same horsepower with a blower or without a blower. The torque may vary. I think its gonna fall on its face with anything bigger than 18s but that is just my opinion. Straight cut 20s max!
 

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The member
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3,244 Posts
David, Remember were not racing in the stone age anymore with 500' starts:D
These thing's need to leave like right now and hard! This sounds like a very similar set up to mine and I ran RB prop with about 800hp and 15s. my boat would spin 8100rpm and run right around 115mph with a donkey driving it.
Hey adam don't put any weight in the boat to slow it down keep it and see if you can run with me??

Oh ya I would start with 18s max ! But what do I know everyone on here has more seat time than me.
 

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Hard Core Member
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406 Posts
Discussion Starter #20
I agree it would launch like a rocket with 18's, I just can't spin 8100 rpm. Not with stock Eagle rods and no bolt upgrade. All I need is to run 9.0, I wouldn''t be surprised if I broke out with what I have. A slightly big gear might be the way to go.

Which makes for an interesting case study, take a motor that went 8.0 @ 140 in a Kurtis 501 and put it in a TR2 with no changes, what will it run?
DJ
 
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