Alpha 1 Gen 2 trim tab position

oldjeep

Admiral
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May 17, 2010
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Changed the prop and had to install an offset trim tab. Don't remember which side the tab was turned to.
help
 

Don S

Honorary Moderator Emeritus
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Re: Alpha 1 Gen 2 trim tab position

Center the tab, run it and adjust as necessary.

trim-tab.jpg
 

oldjeep

Admiral
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May 17, 2010
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Re: Alpha 1 Gen 2 trim tab position

Center the tab, run it and adjust as necessary.

I know, but there is a side it needs to be biased towards just based on prop rotation - figured that someone would know.
 

Oshkosh1

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Jun 8, 2009
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Re: Alpha 1 Gen 2 trim tab position

I know, but there is a side it needs to be biased towards just based on prop rotation - figured that someone would know.

Based on Newtons third law of motion, if you have a clockwise spinning prop, the "P-Factor" is to the left. However there are many variables/imperfections in individual hull and sterndrive setup and/or transducers, pitots etc... that may mitigate or exacerbate this.

So what does this say in a nutshell???

Exactly what Don stated...Put it straight, run it, adjust one "notch" at a time in the direction of your yaw, until the tendency of uncommanded turns one way or the other is gone.

And the smaller offset trim tab may not perform(based on reduced rudder area)as the larger one.

If just countering for torque and nothing else...then you would put it tail to port if looking at it from the stern.
 

oldjeep

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Re: Alpha 1 Gen 2 trim tab position

And the smaller offset trim tab may not perform(based on reduced rudder area)as the larger one.
If just countering for torque and nothing else...then you would put it tail to port if looking at it from the stern.

Thanks. I did use a full sized offset tab, I used a "performance" tab in the past with a different prop and it was fairly useless.
 

Don S

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Re: Alpha 1 Gen 2 trim tab position

Do you have power steering?
 

achris

More fish than mountain goat
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May 19, 2004
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27,468
Re: Alpha 1 Gen 2 trim tab position

Based on Newtons third law of motion, if you have a clockwise spinning prop, the "P-Factor" is to the left. However there are many variables/imperfections in individual hull and sterndrive setup and/or transducers, pitots etc... that may mitigate or exacerbate this.

So what does this say in a nutshell???

Exactly what Don stated...Put it straight, run it, adjust one "notch" at a time in the direction of your yaw, until the tendency of uncommanded turns one way or the other is gone.

And the smaller offset trim tab may not perform(based on reduced rudder area)as the larger one.

If just countering for torque and nothing else...then you would put it tail to port if looking at it from the stern.

And thus completes 'Rocket Science 101'....
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Alpha 1 Gen 2 trim tab position

Power steering is always an option on Mercruiser engines (and sometimes standard fitment)... Maybe the boat dealer didn't want to offer it as an option...

Start with the trailing edge slightly to port, then adjust from there....
 

Don S

Honorary Moderator Emeritus
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Messages
62,321
Re: Alpha 1 Gen 2 trim tab position

Bayliner may have used no-feedback steering in the newer models which would negate any trim tab feedback.
 
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