Zink (Anode) fresh water-salt water

[Jerry San Diego]

I have a 1989, 21 ft Bayliner with a 3.0 L OMC engine and Cobra Outdrive. The boat has been trailerd until now. I am going to keep it in a slip in saltwater in Southern California. I am putting botton pain on the boat and also painting the outdrive. I wanted to check the zinks to see if they had eroded. I took the zinks off and took the to west Marine and compared them to new ones. They appear to be exactly the same size as the new ones and appear to be the same shapes. It would appear the zinks do not need to be changed by their size. They look a little like aluminum does after severaly years. My question is this: The ones at West Marine are noticably heavier in wieght than the ones on my outdrive. The West Marine clerk stated that the ones I have on my boat are for fresh water that is why they are lighter. And also stated they would not function properly in salt water. Does anyone know if this is true. If so is there anything else on my engine that should be changed to allow it to be operated and left in the mater. thankf you.<br />Jerry

 

[rodbolt]

Re: Zink (Anode) fresh water-salt water

Hello<br /> you may have had good advice. merc makes the sacrificial anodes for both fresh and salt water use. in fact the new saltwater anodes are made of an aluminium compound and if the drive suffers any corrsion problems and you have not used the new style merc zincs it will void the warrenty. the freshwater anodes are a magnesium compuond. we used to be able to tell by the weight diffence wich one was wich. Yamaha has gone to the same thing. The other thing to watch on your OMC is the propshaft bearing carrier anode.make sure you have the proper anode for the type of water. and if you trailer the boat use 40 grit sandpaper to clean the anodebefore each launch. if you have never changed the anodes since 1989 they probably have a calcium coating and were no longer working as designed. those anodes must disapear to work.if they aint dissapearing they aint working.the propshaft bearing carrier anode is always overlooked. and its a pain to change. good luck and keep us posted.<br />PS there are some good sites on sacrificial anodes and the MIL-SPEC that goes with them

 

[rodbolt]

Re: Zink (Anode) fresh water-salt water

hello again<br /> I just reread your post. if you paint the outdrive with any anti-fouling paint please insure it is reccommended specifically for drives. regular bottom paint and saltwater will make a pourous mush out of your drive in 3 months.

 

[Lou C]

Re: Zink (Anode) fresh water-salt water

Ditto on the comment on the anti foul for the outdrive. You have to use a tin based paint (Micron 33, Alumaspray are a couple) but these are hard to find because tin based paints are not made any longer due to environmental impact. You can use the newer Trilux for outdrives, but you have to use the special primer so the copper in the trilux does not atttack the alu in the drive. Whatever you do, be aware that all bottom paints are pretty toxic and you MUST wear eye, skin and breathing protection. I let the yard do this one, I looked at a can of the outdrive spray and read the cautions and you don't want to be around this stuff. Next season I may try the Trilux because it can be brushed on so it may not be as hazardous as spraying.

 

[Jerry San Diego]

Re: Zink (Anode) fresh water-salt water

Thanks for the replies- You have all been helpful. I decided to let the boat yard do the painting of the bottom as well as the out drive. I went ahead and purchased new zinks. I was told by the boat yard that my zinks were light because the zink in them were used up, The zink in the propeller shaft appears to be difficult to get to-Has anyone any advice on how big a job it is to get in there and replace it? <br />thanks for the help.