spun hubs

[harryespo]

i am having big trouble with spinning hubs on my twin 250 4 strokes- someone mentioned to me that it could be that my zincs on the cavitation plate are gone and they serve to cool the hubs?? any validity?? My mechanic says they do nothing with the handling of the boat- and serve no purpose except to prevent corrosion. He believes its more likely barnicles or excess water weight causing stress on the hubs OR cavitation from the barnicles. I am at a big loss... any advice will be greatly appreciated.

[99yam40]

I have heard of over heating the hub due to exhaust problems causes hub problems