Question about outdrive steering fin trim tab

indy440

Chief Petty Officer
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Jul 15, 2009
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400
On outboards and outdrives without power steering there is normally a trim tab steering fin just in front of the prop that can be angled to offset the turning effect that the prop torque has on a boat. If this fin is missing or not adjusted properly it can put a huge amount of force back through the steering wheel. In my experience most larger boats with power steering do not have this fin. Apparently the power steering eliminates the feedback through the steering wheel.

A friend of mine has a 23' Century Ultra with a 454mag and Bravo outdrive. It does not have the fin, instead he just has an anode puck where the fin would go. Everything works perfectly and the boat does not pull and there is no feedback through the wheel... except for one time his pump belt popped off the pulley and he had no power steering. It was almost impossible to hold the wheel while getting on plane and there was no way you could go wide open with it, it would just yank the wheel out of your hand and create a very dangerous situation. He is worried that if anything ever went wrong with the power steering while going wide-open at 65mph it could cause a disaster. The wheel would instantly go to one side and possibly spin and flip the boat before he could ever lift the throttle.

Hes wondering if a properly angled trim tab could give him any piece of mind that even with a power steering failure he could control the boat.

The general rule-of-thumb is that for running faster than 70mph requires full hydraulic steering in go-fast boats.

This is the boat:
 

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Bondo

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Re: Question about outdrive steering fin trim tab

Ayuh,... While it Could happen, P/Steering Failures, At Speed are kinda Rare...
Especially on craft that see Regular Maintenance...

Your Bud could Try a tabbed anode, but it might possibly interfere with the Prop...
 

indy440

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Messages
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Re: Question about outdrive steering fin trim tab

I agree they are kind of rare, but when running with high speeds it can be catastrophic. I believe this is the main reason the go-fast guys figure 70mph to be the limit before going to full hydraulic steering...
 

Don S

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Re: Question about outdrive steering fin trim tab

That trim tab is not a good idea. They are usually set for a certain rpm range, and you can feel a pull when rpms are less or more than where it's aimed. To make matters worse, how would you set it? It's a trial and error thing.
If he has a concern, maybe it's time to change the steering system. Either a NFB (No Feed Back) cable steering, or for those speeds, a hydraulic system would be even safer.
 

indy440

Chief Petty Officer
Joined
Jul 15, 2009
Messages
400
Re: Question about outdrive steering fin trim tab

He knows that he needs hydraulic steering to go faster, he was just trying to delay the inevitable (assuming he keeps the boat).

And you're right about the fin being tuned for a specific throttle position, i didnt really think of that. My boat without power steering is the same way, it also pulls differently depending on trim position.
 
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