Zinc shaft donut

[CurtTampa]

The space between the cutless bearing and prop is to tight for one of the tappered zincs. This one is for tighter installs but I'm concerned the inside hole is not concentric with the outside hole. The inner hole has a very slight obling shape. Is this by design? I fear it could cause a vibration issue akin to a tie being out if round. Thoughts/experiences?[/URL]

[deisher6]

Have been replacing the zinc's every 6-12 months with similar ones.  Never paid any attention to the shape except to note they are generally symmetrical. I have a spare on the boat and will check it out next time I get aboard. 

It would be interesting to see how they dynamically balance.

As always a good question.

regards charlie

[MacGyver]

Most zincs arent made perfect so that when they do spin they are as balanced as possible. The oblong shape inside or outside helpswith the balancing from what I have always understood. There is some also that have copper BBs in the inside that press into the zinc more when tightened down in order to help make better contact with the shaft. Typically the shake of the engine and other things just cancel each other out for the most part in the overall picture. That is not to say though that one wouldnt feel a bit more vibration at certain RPMS.

I would say the benefits of such zincs outweighs the vibrations one might feel.

Mac

[Craig]

Mac is right on! Vibration would be minimal and not really noticeable. Where we live not having zincs is unthinkable, especially if the boat is in the water for extended periods!