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Gear Ratio vs acceleration/speed

Old 02-13-2013 | 12:09 AM
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From: Between A Womans Leggs in IL
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Originally Posted by MILD THUNDER
I'd be shooting for the -4 scx lower with #6 prop shafts!
i already mentioned that to him and a smaller diameter prop with your adaptors with the -3's...in one ear and out the other..Some people would rather have it look pirty then have it perform..me paint everything black and fine tune it and lets go boating..

This message has been deleted by mike tkach. Reason: i just dont have the heart to say it.
I do! sorry to hurt feelings but sometimes things need to be said..

Last edited by FIXX; 02-13-2013 at 12:12 AM.
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Old 02-13-2013 | 06:40 AM
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Originally Posted by TunnelVision3100
I agree with you being easier on the drives (strain wise) but one of the biggest factors for killing drives is generating heat as well. Since the 1.36 is spinning faster than the 1.5, what about the extra heat thats being made? Wont that or will that contribute to premature bearing wear?
I believe the 1.36 spins appox 400 rpm faster at 6k then the 1.50, I won't worry about the heat, I run 1.36 with showers no discoloration, This along with Prop Labbing has and always will be trial and error situation. Good luck Keep us posted on the results.

Last edited by abones; 02-13-2013 at 07:34 AM.
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Old 02-13-2013 | 08:22 AM
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Originally Posted by MILD THUNDER
Actually it looks like 1.34 according to this?

http://www.mkhammer.com/imco-sc-lowe...-p-302570.html
i stand corrected.
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Old 02-13-2013 | 08:59 AM
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Originally Posted by mrfixxall
i already mentioned that to him and a smaller diameter prop with your adaptors with the -3's...in one ear and out the other..Some people would rather have it look pirty then have it perform..me paint everything black and fine tune it and lets go boating..



I do! sorry to hurt feelings but sometimes things need to be said..
my deleted post was a wise crack about riverrat ,and it is now just like him,gone!
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Old 02-13-2013 | 10:24 AM
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In all the ones that I have swapped gears in, the 1.34-1.36 does lose a little acceleration as compared to the 1.5. I only change the gears when we just flat out run out of prop. If you can run 1.5's, then I would run them.

I'm in agreement with Joe that an SCX/SCX-4 (depending on X dim.) with a #6 prop shaft would be the way to go. We have done it on a few 42's and they really seem to like it.(again, depending on X dim.) I'm in the middle of dialing one in now. It has an SCX -4 running 17 X 36 5 blades. It was a little to high, along with a few other issues. We've tried a few different spacers to get the X correct. Now that the X is where it needs to be, we are playing with props. If it ever stops raining, we may get to run it.
Eddie
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Old 02-13-2013 | 10:49 AM
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Hey Eddie , you've done a lot with the 42 beakers; what have you found to be a good shaft height relative to the bottom??

Joe
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Old 02-13-2013 | 12:47 PM
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Originally Posted by Young Performance
We've tried a few different spacers to get the X correct. Now that the X is where it needs to be, we are playing with props. If it ever stops raining, we may get to run it.
Eddie
You mean prop shaft height.
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Old 02-13-2013 | 12:49 PM
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With a full stagger and #6 props, about 2" - 2.5" above the bottom seems to be the spot to be.

THe one that I have here now was quite a bit higher than that. The owner installed a -4, so it was ike 4.5" above. The boat got on plane just fine, but wouldn't carry at all. The slip was near 30%. He installed a 1" spacer with little change. I took it out with the 1" and the boat would make a SHARP right turn at 105-110 because it was unloading one of the props. Talk about scare the crap out of you. We almost got pitched out the first time it happened. I then removed the 1"spacer and installled a 2". That put it at about 2.5" above the bottom. It was a totally different boat then. I'm waiting to try another set of props with less rake. He has 18* rake props and it doesn't seem to like them. I found a set that are the same size with only 16*, so I want to try them.
Eddie
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Old 02-13-2013 | 01:49 PM
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I know a lot of time the 1.36 is used to cure the "running out of prop" issue but doesn't the 1.36 also help reduce the stress on the drive and make it live longer behind bigger HP? I have a 1.36 drive behind my 22 Velocity and its not really needed but I had it and it pulls pretty good with a 24 Bravo. I still have the 1.5 drive that came on the boat and after hearing what everyone is saying I am thinking about trying it this summer with a different pitch prop to see how it affects my top speed. So far with the 1.36 drive at 5270 rpms I have run 77 GPS mph. If I can run a 1.5 drive and get the same style prop to get me to the 52-5300 rpm range will I pick up more speed? My boat gets on plane easy now with 450 hp and the 1.36 drive so planing is not a issue with the 1.36 for me.
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Old 02-13-2013 | 03:24 PM
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Originally Posted by Young Performance
With a full stagger and #6 props, about 2" - 2.5" above the bottom seems to be the spot to be.

THe one that I have here now was quite a bit higher than that. The owner installed a -4, so it was ike 4.5" above. The boat got on plane just fine, but wouldn't carry at all. The slip was near 30%. He installed a 1" spacer with little change. I took it out with the 1" and the boat would make a SHARP right turn at 105-110 because it was unloading one of the props. Talk about scare the crap out of you. We almost got pitched out the first time it happened. I then removed the 1"spacer and installled a 2". That put it at about 2.5" above the bottom. It was a totally different boat then. I'm waiting to try another set of props with less rake. He has 18* rake props and it doesn't seem to like them. I found a set that are the same size with only 16*, so I want to try them.
Eddie
I need to measure Joe's. His hull is a 96. I told him 1,2,3,4'' shorties don't really mean anything, as its all about where the shafts end up relative to the bottom. I'd imagine his drive height was rigged more conservative than say a 2006 42.

I don't really like the idea of going to high with the bravo style props. With a -1 lower, if the numbers he gave me are true, then his slip is good at 10% with a 4 blade bravo. Almost too good to believe. We'll see come spring.

That's scary aeriating a prop at 110mph! Do you think the bullet was skating on top at that speed?
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