Zincs on outboards

[Bill Jarrell]

Hello all,
Have a question regarding sacrificial zincs on outboard motors. With my new CD25 I acquired a used 5 hp Nissan that need its zinc replaced.
Here is my question:

On my previous outboard I drilled thru the cavitation plate and screwed a set of zinc rudder buttons (around $3.00 a set) one to the top and one to the bottom of the outboards's cavitation plate. I drilled the screw hole slightly smaller so I got good metal to metal contact with the zinc and plate. This arrangement appeared to work well and gave me plenty of zinc. When I pulled the motor out for the season I could see that the zinc had degraded, so it appeared to be doing its job; it was streamlined; and you were able to see the status of the zinc without having to take the outboard out of the water to inspect under the caviation plate.

However in the dark of the night when we are alone and all our boat worries come to haunt us, I began to have a question about my arrangement. Let me try and explain. The original zinc attachment is made thru a SS screw located under the cavitation plate next to the water intake. Here is my question. Is there some sort of contact the SS screw makes inside of the lower unit that my arrangement fails to provide? With my arrangement, is my lower unit secretly turning into white powder? As you can see this is definitely a 3am in the morning type of question.

Hopefully, your comments will allow me to blissfully sleep thru the night.

Thanks

Bill

[winthrop fisher]

yes you need it on your out board zinc.
it should be fine.

[bgephart]

I have been attaching zincs to the cavitation plate on OMC outboards for over 20 years in salt / brackish water in Savannah, with excellent results. My last motor lasted about 14 years, and then it was a fuel system that killed it - the lower unit was fine. The only point I would add to your post is that I attach the zinc using brass screws to assure excellent electrical transfer to the cavitation plate. While I need to replace the cavitation plate zinc every year, the anode that fits up into the center of the foot has lasted three years so far with very little metal loss.

Sleep well !!!

[tartansailor]

Bill,
First congratulations on your good taste in boats, and we hope that you have many happy years with it.

The zinc on my Honda outboard is configured with 2 SS bolts thru the bottom of the cavitation plate then up into the zinc.

It appears to me that the designers intended to have a zinc to aluminum contact, as there is no paint at the aluminum mating surface.

Dick