Zinc anode

[Tim Frank]

I have a 2005 Nissan 40 HP 2-stroke.
I have just noticed that it does not have a zinc anode on the lower unit.
It is only used in fresh water, but it is no doubt still a good idea to have one.
Is this as straight forward to add as it seems, or are there any "landmines" to avoid?

 

[psteurer]

Re: Zinc anode

Did this motor have one to begin with and you are just replacing it? If so, it is pretty easy to replace. If not, you would have to decide where to put it and then drill some holes. The key is to make sure you have the anode installed so that it can conduct the current from the motor to the anode which could involve removing some paint.

Before doing this, you also might want to check around the transom bracket. Some of the newer motors have the anode located there and not on the lower unit cavitation plate as was done previously.

 

[Tim Frank]

Re: Zinc anode

I never looked previously, but noticed when I put it away this fall that it did not have one.
Have not checked the transom bracket, will do that.
Otherwise, I will just drill a couple of holes and sand off a bit of paint....

Thanks.

BTW, nice lines and ride on that boat in your avatar.....is it a tinny?

 

[psteurer]

Re: Zinc anode

Yes, my boat is a 1963 aluminum Sea King sold by Montgomery Wards. I think it was made by Starcraft.

I bet you motor has an anode somewhere. Maybe someone more knowledgeable will respond here before you drill.

 

[robert graham]

Re: Zinc anode

Some motors have anodes inside and outside. Does your motor have a trim tab under the cavitation plate? They usually double for an anode. I'm not sure about what year the motor manufacturers started using anodes.

 

[TOHATSU GURU]

Re: Zinc anode

It takes the trim tab type on the 40 C and a bracket and trim tab type on the 40 D.

 

[smsscuba]

Re: Zinc anode

A question came to mind about the anode,if this outboard is only used in fresh water, then a zinc anode will be useless.Should a magnesium anode rather be used?

 

[pvanv]

Re: Zinc anode

A question came to mind about the anode,if this outboard is only used in fresh water, then a zinc anode will be useless.Should a magnesium anode rather be used?

False. Anodes are needed any time dissimilar metals are immersed in any electrolyte, including freshwater. In fact, a lot of domestic hot water tanks (used on land, and definitely fresh water), have sacrificial anodes.

There are aftermarket anodes specifically for freshwater, but maybe not for that particular application, especially if it's the trim tab type..

The warmer the water, the saltier the water, the longer the immersion, the more dissimilar the underwater metals on the boat, the more the corrosion. Better to sacrifice the less noble "sacrificial anode" than the LU.

 

[smsscuba]

Re: Zinc anode

I looked about on the internet and it is stated that a magnesium anode be used if the outboard is to be used for prolonged hours in freshwater.
As quoted:

Should a vessel move into fresh water for more than two weeks MGDUFF recommend that an alternative anode system is used suitable for fresh water situations. Magnesium Anodes on the other hand have a much higher driving voltage than zinc or aluminium making them highly suitable for use in Fresh Water, they will however become very active in salt water where they will probably only last a matter of months. Protected surfaces can build up a layer of off white calcareous deposit which will be difficult to remove. Magnesium anodes are not designed for prolonged use in sea water and if you are taking your boat into a salt water location for more than seven days (Fourteen days in any one year) you should consider changing the anodes. Magnesium Anodes should never be fitted to wooden hulled vessels as they can damage the timber. - MG DUFF

 

[TOHATSU GURU]

Re: Zinc anode

It's a pointless "what if" my friend. The anode in question doubles as a trim tab. The likelihood of finding a mag anode that fits into the cut out and corrects torque as needed is so remote as to not be worth the trouble to find it.