Gear Ratio vs acceleration/speed
02-13-2013 | 06:19 PM
#31
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From: Tennessee
If the boat is that old, then you can count on the drive being fairly low. The one I have here is a 99, but it was re-rigged in 09 to the current specs at that time. So, it has a fairly high X. That's why the -4 was too high.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
02-13-2013 | 07:33 PM
#32
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Joined: Jul 2004
Posts: 11,332
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From: chicago
If the boat is that old, then you can count on the drive being fairly low. The one I have here is a 99, but it was re-rigged in 09 to the current specs at that time. So, it has a fairly high X. That's why the -4 was too high.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
Scary man! I know he tried the -3 lowers, and he said it planed no problem at all. I need to measure his shaft height....wait that sounds bad.
02-13-2013 | 08:20 PM
#33
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Joined: Aug 2005
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From: Between A Womans Leggs in IL
If the boat is that old, then you can count on the drive being fairly low. The one I have here is a 99, but it was re-rigged in 09 to the current specs at that time. So, it has a fairly high X. That's why the -4 was too high.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
If he is truly getting 10% slip with 4 blade Bravo prop, then it must be pretty deep. These boats seem to respond very well to higher X dim., at least with the #6 props. He obviously won't be able to get that 4 blade to close to the surface. It he wants to get the most out of it, then he needs to go to the 6 props and raise them up.
It was a very scary ride when the boat hooked at over 100. I would have bet any amount that we were going swimming. I came out of the seat enough to pull the kill switches. That's why I always wear them.
02-13-2013 | 11:19 PM
#34
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From: Tennessee
Eddie
02-18-2013 | 08:23 AM
#35
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Joined: Sep 2003
Posts: 521
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From: Fort Erie Ontario Canada
in the 07 38 fountains with 600 sci's , ITS bravo drives, they came with 1.36 and 1.50 gear ratio, same top end speed and rpm's. I don't know why but they did. They where not running out of prop with the 1.50. Some had merc props some had herrings.
Mine had the 1.36 and 32 6 blade herrings and I did an whipple upgrade and can't believe how it pulls thru midrange, I go easy on it to save the gears.
I would think if the 1.36 is propped for a certain rpm, and the 1.50 is propped for the same rpm the acceleration should be pretty close to the same .
Mine had the 1.36 and 32 6 blade herrings and I did an whipple upgrade and can't believe how it pulls thru midrange, I go easy on it to save the gears.
I would think if the 1.36 is propped for a certain rpm, and the 1.50 is propped for the same rpm the acceleration should be pretty close to the same .
02-19-2013 | 07:56 PM
#36
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Joined: May 2007
Posts: 1,351
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From: KC, MO
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
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
