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#6 Top Gun straight bottom drive height

Old 08-07-2020, 10:43 AM
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Default #6 Top Gun straight bottom drive height

I have a factory #6 95 Top Gun, appropriately named the Kangaroo Rat because it hops like a Kangaroo. This is more than the standard Top Gun porpoise, this gets violent at high speeds unless the boat is run extremely wet. Talking to people familiar with the boat from way back when, I have gotten conflicting reports on whether the boat came factory with boxes or not. Everybody did say though that back when this boat was new, it handled like it was on rails and it was very fast. It is neither of those things for me. Right now it does not have boxes and has wet sump 6's. I think the drive height may just be too high and this could be a significant part of the problem. When trimming up, when the porpoise starts it feels like the props are losing bite and the bow comes down, then they regain bite and the process starts all over. I would like to know where these drives should be height wise for the best performance. I have tried various diameter 4 blade and 5 blade props, spinning in or spinning out, and nothing simple like that is helping the issue. If anybody familiar with these boats and this setup could shed some light on what drive height works best I would greatly appreciate it.
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Old 08-07-2020, 11:08 AM
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wheres the prop shaft sitting now
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Old 08-07-2020, 12:13 PM
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Old school II prop shafts are 1 below the running surface, when I ran that boat a few years ago it had a slight porpoise with one set of props, bad porpoise with the others. I know they were both 4 blades but dont remember any other specs.
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Old 08-07-2020, 02:11 PM
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Originally Posted by F-2 Speedy View Post
wheres the prop shaft sitting now
1" below the notch.
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Old 08-07-2020, 02:17 PM
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Does it still have ten tons of stereo equipment in it? I'm guessing that doesn't help the CG
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Old 08-07-2020, 02:20 PM
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Originally Posted by donzi matt View Post
1" below the notch.
how about in relation to the bottom of the boat?
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Old 08-07-2020, 02:58 PM
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Originally Posted by donzi matt View Post
1" below the notch.
top of the notch ?
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Old 08-08-2020, 05:04 AM
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Originally Posted by thisistank View Post
Does it still have ten tons of stereo equipment in it? I'm guessing that doesn't help the CG
It doesn't have all the equipment, but it still has a fair bit of it, yes. She's a girthy girl.
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Old 08-08-2020, 05:05 AM
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Originally Posted by Unlimited jd View Post
how about in relation to the bottom of the boat?
The drives are 1" below the top of the notch or 2&1/4" above the bottom of the boat inline with the propshafts.
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Old 08-08-2020, 06:31 AM
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Originally Posted by donzi matt View Post
The drives are 1" below the top of the notch or 2&1/4" above the bottom of the boat inline with the propshafts.
being that high, Im sure that boat had boxes on it before. Put a 1.5 spacer in and it should help a ton
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