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Cavitation Fin Adjustment

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Fisherman_7

Member
I just recently changed out my older motor to a newer one. Everything is fine except, the boat wants to pull to the right at higher traveling speed. Am I correct by adjusting the cavitation fin which is located under the plate on the lower unit will correct the pull? Also do you adjust it to the same direction of the pull? I have an Evinrude 150HP. Any suggestions would be appreciated. Thanks
 
If it pulls to the right then you need to move the trailing edge of the fin to the right so it counter steers the motor to the left. You will probably find it doesn't have the same effect throughout the whole speed range so you will have to optimize it for your cruising speed.
 
chessbass said:
Shouldn't the adjustment be to move the "leading edge"?
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Tell us how one would do that... the tension/lock bolt is dead center of the trim tab, the adjusting tab being aft of that bolt with the procedure being to move the tab in the direction of the pulling action.
 
True! Trailing edge moved to right forces trailing edge of engine to the left which in turn forces stern to right and bow to left. Newton's Third Law!
 
Guys, thanks so much for verifying that for me. That's why when I have a problem with boat or motor, you guys are experts, I come here to get my answers. Thank You again.
 
bill_w said:
if you really want to get technical, it's an "anti-ventilation plate", not a cavitation fin
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Bill... The poster's question pertains to the "trim tab" which is attached to the bottom portion of the "cavitation plate" that exists above the propeller. Not trying to be technical... just pointing out that it's best to call a spade a spade so to speak.

Same reason we do not call a "spark plug" one of those "shocky things". :)
 
That always was a confusing term. My dad, who built and raced outboards, always called it a "cavitation plate", but I've heard it called the "anti-ventilation" plate by some manuals and technicians. My understanding is that it blocks air from being sucked in by the spinning propeller, causing the prop to just grab air instead of water, similar to the effect when you trim the engine too high when it is running. Of course, cavitation is described as air bubbles on the propeller that cause corrosion and pitting. Sounds like the "plate" serves a dual purpose.
 
kimcrwbr1 said:
Cavitation is when a nick in the prop creates a negative pressure and causes the water to boil converting water to hydrogen and oxygen or from liquid to gas. The effect is exactly the same as when the prop is ventilating or sucking air.
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Well, As Janis (Janice?) on Friends would say..... Oh...My...God! :)
 
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