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Old 07-17-2019, 08:31 AM
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Try a different set of props. See if they have the same rpm problem.
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Old 07-17-2019, 11:19 AM
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One drive is chain driven, the other is gear driven (to change rotation). The gear drive box is less efficient than the chain drive and will extract more power but I wouldn't think it would 15%. Do you know which side the gear drive box is on?
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Old 07-17-2019, 05:39 PM
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You might be able to put synthetic oil in the slow side gear box.
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Old 07-17-2019, 07:34 PM
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Originally Posted by payuppsucker View Post
One drive is chain driven, the other is gear driven (to change rotation). The gear drive box is less efficient than the chain drive and will extract more power but I wouldn't think it would 15%. Do you know which side the gear drive box is on?
I believe the ZF 280's are gear only. Basically one is in reverse and one in forward. Typical three shaft transmission with an input, a lay, and output shaft. The side that's down on RPM is the one that has more gear contact to rotate same as the motor. I can't imagine it's 15% though.
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Old 07-17-2019, 07:39 PM
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Originally Posted by Tmaddox4x4 View Post



I believe the ZF 280's are gear only. Basically one is in reverse and one in forward. Typical three shaft transmission with an input, a lay, and output shaft. The side that's down on RPM is the one that has more gear contact to rotate same as the motor. I can't imagine it's 15% though.
Agreed, 15% is a lot.
What horsepower are you making?
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Old 07-17-2019, 07:46 PM
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Hold on, let’s back up a bit......
I am talking about the ASD8 drives, not the transmissions.
So are you saying the counter rotation is accomplished in the transmissions rather than the drives?
I am not well versed on the ASD8 but assumed it was similar to the ASD7 which uses gears to reverse rotation on one drive and a chain/sprocket combo on the other drive.
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Old 07-17-2019, 07:48 PM
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Originally Posted by payuppsucker View Post

Agreed, 15% is a lot.
What horsepower are you making?
They are the 480HP 950TQ rated motors. I just had the the first 250 hour service done on them. We checked the valve lash and injectors, and a few other things. I'm really leaning towards the props, it makes the most sense. My only experience with surface drives is with RC boats. I do know that a very small change in prop makes a huge difference. Granted, that probably not the best comparison.
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Old 07-17-2019, 07:57 PM
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Originally Posted by payuppsucker View Post
Hold on, let’s back up a bit......
I am talking about the ASD8 drives, not the transmissions.
So are you saying the counter rotation is accomplished in the transmissions rather than the drives?
I am not well versed on the ASD8 but assumed it was similar to the ASD7 which uses gears to reverse rotation on one drive and a chain/sprocket combo on the other drive.
My Arnesons don't have a gear box. They are connected straight to the trans output. My trans are 1.118:1 ratio, basically direct drive. My motors sit incredibly low and the transmission takes care of the drop. The output flange is also at a 7° down angle.
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Old 07-17-2019, 08:16 PM
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Ok, well excuse my ignorance and I learned something here.
If you have #6 props I have a spare set if you’d like to try them.
They are considerably smaller than what you are running though.
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Old 07-17-2019, 09:41 PM
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Last thing I can come up with is one intercooler is clogged with soot.
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