Removing Zinc from Bot. Yamaha Engine Bracket

[Nickc]

Trying to remove Zinc from Bottom of Engine Bracket of My Yamaha 200Hp on my 2019 Ranger Tug. The zinc is almost totally eaten away by galvanic action. The large zinc (approx 2"x7") is held in place by 4- #10 stainless screws. I tried using some WD40 on all screws, but I am leery of putting any more force on socket wrench since I believe it is starting to distort with only minimal force.
I am thinking of removing the remaining soft zinc around the screws so I can get a vice grip along w/socket wrench around the shank of the #10 screws. Will heat from a torch and/or another brand of penetrating fluid help in my efforts not to shear off these screws in the bracket? Also if I remove the screws successfully- is there something to coat the screws so it doesn't get seized in there again?

 

[BB marine]

Heat will help but be careful there are teflon bushings used in the midsections and transom bracket. I would soak the bolts with a good penetrant and use a 6 point socket. I would try a impact driver https://cdn.mscdirect.com/global/images ... 940-11.jpg

I have used this successfully removing corroded or rusted fasteners. It shocks the bolt has it trys to loosen it. I will impact the bolt left hand to loosen then switch it to right hand. shocking the bolt both ways until it frees up. Patience and persistence will release the bolts from the housing.

I'm not sure of the size of the bolts. I believe they would be a M6x 1 metric bolt make sure you are using a metric socket.

 

[Nickc]

Thanks for response! BB Marine-always so responsive!
I will give it a shot tomorrow and let you know how it goes..
NickC

 

[dclagett]

I replace the external anodes every year even if they still look good just so I don’t get into a corrosion problem with stuck bolts, nuts, etc. Anodes are cheap. In addition, when I had outboards, I followed the manufacturer maintenance schedule to the letter, especially for the lower unit maintenance because of potential corrosion issues. An example of what can happen with lower units that are not maintained well: last week while I was working on my boat I watched two certified Yamaha mechanics try to replace the seals in a lower unit that had water in the oil. They worked for 3 days trying to disassemble the unit and finally gave up. A new lower unit was ordered. Think about the cost, over $5K for the unit and labor for 3 days plus.

 

[Capt’nKarl]

Also remember to use some Anti-Seize. Remove any old stuff and replace with new.

 

[Nickc]

BB. I see from your image that this is a hand impact driver ( Proto3/8" Hand Impact Socket Driver
5-1/2" OAL MSC it#85209401) ....so I assume ft/lb impact torque is low enough not to shear off the 10mm stainless screw-- the MSC web site doesn't list any specifications. I will go carefully.. not sure penetrant is getting to threads since gravity is working against gravity.. the facing up screws. Will let you know how it goes.( I really don't to have drill sheared studs and helicoil.)
(PS DC & CaptKarl...engine/Boat is 2ys old and in salt water .. I am second owner.. and yes... zincs were never changed..the pancake anode under the cavitation plate was completely disintegrated/gone.. only bolt in lower unit housing remains! ... you can be sure I will change ever season and use Anti seize/ new screws)

 

[ALICE J]

Try Tuff Gel for the anti-seizing. Comes in a syringe and only needs a little dab. It's white and very sticky, try not to get your fingers in it, it's just messy. 😱

 

[knotflying]

Sometimes tightening a little helps release it. PB Blaster works well also.

 

[BB marine]

.so I assume ft/lb impact torque is low enough not to shear off the 10mm stainless screw--

The hand impact will or can apply enough torque to break the screw. The chances of breaking the screw using the impact are less than if you used a racket socket or wrench. The purpose of the impact is to free the frozen bolt by shocking it with a torsional force. I have good success using this method. When you strike the impact use one hand to turn the impact wrench left hand (loosen) do this 3 to 4 times. Shift the impact to right hand use one hand to turn the impact right hand. This is shocking the bolt. After doing this spray the bolts, anode, and complete bottom section of the transom bracket. Don't be conservative with the penetrant. Use a wire brush to clean the bolt contact area to help the penetrant find paths to work. If the anode is Zinc use a particulate mask when wire brushing. Repeat the impact procedure again. When you feel some movement in the bolt you're not done working it. When you feel movement say 1/4 or 1/2 turn left hand turn. Stop saturate the bolt with penetrant again then turn the bolt right hand 1/4 to 1/2 turn This helps pull penetrant into the threads of the housing. Work the bolt back and forth. Now use the impact again using your hand to turn the impact as you hit the impact with a hammer. When you get another 1/2 turn. Stop repeat the last steps more penetrant and work the bolt back and forth. 1 turn right 1 turn left. At this point using a socket and ratchet for removal should work. Continue to work the bolt back and forth as you remove it. Good luck, I have had success many times using this method. I will warn you that I have still had to drill bolts out of aluminum outboard housings too. Sometimes it is inevitable. I will spend an extra hour trying to prevent the inevitable!!!

 

[Nickc]

tks got it .. will let you know how it goes
NickC

 

[Nickc]

After using BB's methods of trying to remove the 2 seized screws on the right side of my Yamaha Engine backet--- I left it to the yard I had it in last winter- to remove and put on a new anode. The Yard proceeded to shear off the 2 screws on the right side and put boat in water with 2 screws on the left side only. After another yard hauled boat last fall --- the anode showed evidence that apparently it was working -- and was still about 75% intact. This season-- rather than trying to drill-out/remove the 2 sheared off screws--- I was considering drilling 1 hole in between the 2 sheared off screw holes on the anode/engine bracket-- and drilling/taping/replacing only 1 screw to hold the anode on that side.
Any comments/thoughts appreciated. Also wondering if drilling an additional hole in the engine bracket would have negative structural effect on the engine bracket?