Zinc anodes on a boat

[John W. Grimstad]

I have a 100hp mercury and am wondering how important the zinc plates are? I live in Montana and use my boat only in the summer months and only on weekends.

Some of the local dealers couldn't really answere the questions. Some say it is needed and other say mainly for salt water?!?!

Any info would be appreciated.

Thanks,
John

[Anode Guy]

An anode helps protect the outboard against galvanic corrosion by sacrificing its metal to be slowly erroded instead of the outboard metals.

Although you do not boat in salt water, you still have corrosive chemicals in freshwater. Periodic inspection of the anode will maintain that the motor's metals will remain intact.

[Kaz]

John: I too have some electrolysis even though my motor is in fresh water. If you trail your boat, then it should not show any signs of corrosion. On my aluminum pontoon, if I leave the motor down, then it starts attacking the zinc pad. If you can, leave the donor pad in place, just for the safety of the lower unit. We never had these problems before all of the electronic gear and the big batterys....Kaz

[Daren]

It's a good ideal to leave them on as stated. In addition to corrosive materials that may be in the water, you also have a static charge that builds up when using the motor. This occurs just like when you rub your feet on the carpet. It occurs between the water you are moving across and the boat. Without the sacrificial anodes you will have a far greater chance of having corrosion occur on the boat (if alluminum) and motor. Also, on many outboards, the sacrificial anode is found above the prop and has a small keel to it. This is set either to the left or right to counter some of the torque of the motor. Without this you can actually loose performance and have a little harder time steering the motor. Usually not a big difference but it is there. For the best protection from corrosion for the motor this anode should not be painted.

[John]

Thanks for the input. I will get the zinc and put it on. Better safe then sorry....

John

[Bob from Detroit]

Most professionals recommend magnesium anodes for fresh water and zinc for salt water. (Check BoatUS catalog page #657. I would guess West Marine would say the same.)

[CarpetBagger]

Your right however there are only certain Fresh Water ones made for the lower units. The fresh water anodes are made out of Magnesium not Zinc...

CB