How to replace the fin above the prop.

Fordiesel69 · Oct 16, 2009

On my bayliner this fin was snapped off since I got it. I also hear this is adjustable. I can get one online for $9 and was wondering how you change it or adjust it?

Twinz · Oct 16, 2009

Re: How to replace the fin above the prop.

There is a cap above the "fin" on the outdrive. Pop this off and insert a socket (not sure what size) and off it comes.

Aviator5 · Oct 16, 2009

Re: How to replace the fin above the prop.

Not socket, but allen wrench.

ErieRon · Oct 16, 2009

Re: How to replace the fin above the prop.

Directly above the "fin" (or trim tab) there is a hole in the outdrive (sometimes has a plastic cap in it). Down inside that hole is a socket head cap screw. You need an allen wrench (can't remember the size 5/16 or 3/8 maybe) to loosen the screw then the trim tab can be removed. It's usually corroded a bit, so you may have to tap it some...be gentle though

It's used to counter the torque from the prop rotation and is adjustable.

ziggy · Oct 16, 2009

Re: How to replace the fin above the prop.

on my old drive. the bolt drive is a hex wrench. allen wrench, whatever ya wanna call it. it drives a cap screw.. size. ? 3/8"? can't remember..
i agree with er. that bolt will corrode in place. i use a little pb blaster on it prior to trying to remove it..

Fordiesel69 · Oct 16, 2009

Re: How to replace the fin above the prop.

Thanks, I would have never guessed it.

My symptom is horrible tracking at slow no wake speeds. I have to constantly over correct the steering as it wants to drift side to side. Once powered up, it feels fine. I was told a new fin will fix this.

Knightgang · Oct 16, 2009

Re: How to replace the fin above the prop.

Yep, they are right. All outdrives have them in some form. On outboards, they are bolted from underneath.

Maclin · Oct 16, 2009

Re: How to replace the fin above the prop.

Fordiesel69 said:
Thanks, I would have never guessed it.

My symptom is horrible tracking at slow no wake speeds. I have to constantly over correct the steering as it wants to drift side to side. Once powered up, it feels fine. I was told a new fin will fix this.

That is low speed wander and is typical of sterndrive boats. That fin has little effect at no wake speeds, it is there to offset the thrust of the prop during take off and higher speed cruising to keep it tracking straight. I am not saying you do not need one but I think you will be disappointed in this regard.

Aviator5 · Oct 16, 2009

Re: How to replace the fin above the prop.

It is also a sacrificial anode to protect your outdrive from corrosion.

Bart Sr. · Oct 16, 2009

Re: How to replace the fin above the prop.

Fordiesel69 said:
I have to constantly over correct the steering as it wants to drift side to side.

Making smaller corrections reduces the wander.After more practice it will be second nature.By the middle of my first full season it was easy.

83Evinrude · Oct 16, 2009

Re: How to replace the fin above the prop.

Knightgang said:
All outdrives have them in some form.

My Volvo SX doesn't have a trim fin and I didn't think most outdrives with power steering did.

Glastron_V210 · Oct 16, 2009

Re: How to replace the fin above the prop.

Check your steering also....have someone inside the boat turn the wheel while you hold the outdrive....any slop?

If not it's just deep v wander, perfectly normal and annoying.

C

Fordiesel69 · Oct 16, 2009

Re: How to replace the fin above the prop.

That sucks, I just went to put it on and found that the PO broke it off for a good reason. The prop HITS!!!!!!!

Can I just grind a section out so the prop clears? If so how much space do I need?

sdoomaha · Oct 16, 2009

Re: How to replace the fin above the prop.

They make a smaller one for performance props. I had to switch mine over to the smaller one when I put on a cleaver prop. Rather than making fit, you might be better off taking it back and getting the proper one.

Take care,

Dshow · Oct 16, 2009

Re: How to replace the fin above the prop.

If you have power steering, it may not have a fin at all. Mine is flat.

Rocky_Road · Oct 16, 2009

Re: How to replace the fin above the prop.

Fordiesel69 said:
That sucks, I just went to put it on and found that the PO broke it off for a good reason. The prop HITS!!!!!!!

Can I just grind a section out so the prop clears? If so how much space do I need?

Some people file (grind) enough for clearance...I used this one from Mercruiser:

cr2k · Oct 16, 2009

Re: How to replace the fin above the prop.

I have found that the wonder goes back and forth the same amount.
At least on my Regal. So I just set it to the center of where I am headed and let it go back and forth. Sure saves arm and wrist pump from fighting it.

And yes you can grind/file it to clear your prop. I would give it 3/8 to 1/2 in. clearance. More toward 1/2 if you have a rubber hub prop.

Some have 1/2 in bolt, some have 5/16 or 3/8 allen head, depends on year and model.

ziggy · Oct 17, 2009

Re: How to replace the fin above the prop.

And yes you can grind/file it to clear your prop.

ditto. i've even read it in a merc. s/m somewhere. can't remember where. maybe #6..
mine hit too. heres how my grind job turned out.

i've had zero issues from the grind and the prop is just what my rig needed. hope yours turns out as well..

rebars1 · Oct 17, 2009

Re: How to replace the fin above the prop.

I had to do that on mine , too. Make sure you round off the front edge and keep it smooth.

mcleaves · Oct 17, 2009

Re: How to replace the fin above the prop.

83Evinrude said:
My Volvo SX doesn't have a trim fin and I didn't think most outdrives with power steering did.

+1..

Pretty sure the fins are only for non-power steering applications

Don has a good picture of what angle to set the fin to counter the rotation of the prop and if the boat is pulling.

How to replace the fin above the prop.

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