Cavitation Plate Anode Fin Alignment

[jason78]

I lost the anode off the cavitation plate last season. This is the one mounted right above the prop. Mine had a small fin on it. It was turned off center but I do not remember the angle. What is the purpose of the fin on this anode and how do I ever tell how to make sure its replacement is installed at the proper angle when I replace it? Is there a set angle or is it adjusted on a per unit basis?

Thanks!
Jason

[OldTimer57]

It is an anti-torque tab. You generally adjust it to make steering wheel remain neutral when going straight ahead, and not pulling to either side. However, MOST are ineffective unless you have the motor buried. High performance boats run the motor so high that little fin is out of the water. And most bigger outboards come with a flat anode plate with no find there for that same reason.

Note that this works best at a specific RPM and trim setting. So you obviously want to set it when the boat is running at your normal cruise speed.

[JOE54]

trailing edge of fin offset to stbd side

[jason78]

Thank you both for the advice!

[leonreno]

And it really is designed for mechanical cable steering systems, with hydraulic steering just set it in the middle and your good to go.

[jethro1]

And it really is designed for mechanical cable steering systems, with hydraulic steering just set it in the middle and your good to go.

That has not been my experience. Even with hydraulic steering, if the trim tab is not properly positioned, the effort to turn right or left will not be the same. By making an adjustment to the trim tab the steering effort can be made to be the same, right turn or left turn, when the engine is trimmed to its normal trim angle.

[Blue Dog]

I have a 150 opti 25" shaft with Hydraulic steering on my 20' center console and have the anode with no fin. It tracks in a straight line on plane with no hands on the wheel.

I'm running a 17P 3 blade stainless prop that does not cavitate on a hard turn. And top speed on my boat is 49 MPH (very slow for guys on this site).

I suspect it might be different running a short shaft motor, high pitch prop at 70+ MPH.

[jethro1]

I have a 150 opti 25" shaft with Hydraulic steering on my 20' center console and have the anode with no fin. It tracks in a straight line on plane with no hands on the wheel.

I'm running a 17P 3 blade stainless prop that does not cavitate on a hard turn. And top speed on my boat is 49 MPH (very slow for guys on this site).

I suspect it might be different running a short shaft motor, high pitch prop at 70+ MPH.

Is the effort to turn the same to the right as to the left?

[EuropeanAM]

I lost the anode off the cavitation plate last season. This is the one mounted right above the prop. Mine had a small fin on it. It was turned off center but I do not remember the angle. What is the purpose of the fin on this anode and how do I ever tell how to make sure its replacement is installed at the proper angle when I replace it? Is there a set angle or is it adjusted on a per unit basis?

Thanks!
Jason

Let's stick with this ONE engine. Please see the Forum Announcements, and be sure to provide the REQUIRED info when posting. Thanks!

Are you using HYDRAULIC or CABLE steering?

[jason78]

Let's stick with this ONE engine. Please see the Forum Announcements, and be sure to provide the REQUIRED info when posting. Thanks!

Are you using HYDRAULIC or CABLE steering?

I have a 1998 Mercury 200XL Offshore Outboard with Sea Star Hydraulic Steering. Thanks

[EuropeanAM]

As stated earlier in the thread, a FLAT anode plate is most commonly used with hydraulic steering- IF you choose to install a trim tab, it will normally be offset slightly to the STB side (the aft or rear end of the fin slightly offset to Starboard or Right side).

I'd recommend the flat-plate anode.

[jason78]

Just want to thank everyone. I had already ordered a trim tab by the time I saw the suggestions about the flat-plate. I installed it as directed and the boat seemed to track well. Not sure if it had any impact since I have hydraulic steering but either way, I have a missing part now replaced. Thanks!