Stopping Corrosion

[AMcCall]

I've got an early 80's johnson outboard that has some corrosion on the lower unit and exhaust housing. I've thought about repainting it, but am wondering what I can do to stop the corrosion. Would sanding the corroded areas and then priming with zinc chromate and painting stop the corrosion?

 

[CATransplant]

Re: Stopping Corrosion

Is this outboard in fresh or salt water? Different approaches, depending. Also, what model outboard is this?

 

[umblecumbuz]

Re: Stopping Corrosion

You need to do two things AM, and they're not really interrelated.<br /><br />Clean, prime and paint as you said. That'll keep the corroded areas covered.<br /><br />Fit zincs on the leg to stop galvanic corrosion. If you don't, you'll only be papering over the cracks, because if galvanic corrosion has caused your problem, it will continue unseen inside the motor, without 'zinc' protection.

 

[umblecumbuz]

Re: Stopping Corrosion

Dang it CA - how come we often post at exactly the same time, but your's always gets there first?

 

[AMcCall]

Re: Stopping Corrosion

The model is J35ELCND. I will only use it in fresh water, but I'm not sure of the history...it may have seen some salt. I believe it previously had a stainless prop on it, if that makes any difference.<br /><br />I'll definitely prime, paint, and get some zincs.

 

[umblecumbuz]

Re: Stopping Corrosion

AM,<br /><br />You've possibly nailed it. If it was previously run in salt with a stainless prop, and it wasn't cared for properly, then the stainless prop could have accelerated the corrosion on the leg.<br /><br />The reason is that the leg would start to 'sacrifice'itself to protect the stainless. This doesn't happen anywhere near as fast if the prop is aluminum, because the aluminum is nearer to the alloy leg on the galvanic scale. The principle is that the further apart any two metals are on the galvanic table, the quicker the 'lesser' metal will corrode.<br /><br />Keep your boat warm, dry and never take it near water, and you'll avoid all galvanic corrosion problems!

 

[Dunaruna]

Re: Stopping Corrosion

Interesting, nobody has mentioned magnesium anodes.