How Much Protection Does Prop Zinc Offer Engine Cooling System ?

[yamaha30c]

My engine block zinc bolt is stuck and a square bolt head is almost round now. The final option is to remove the head of the cooling portion of my yanmar YC engine and remove the zinc but that would be a more complicated operation that would require finding the right replacement packing/gaskets from Yanmar.

I have zincs on my prop shaft. They are technically electrically connected to the cooling system thru the engine and the shaft and share the same seawater which runs thru my direct cooling system. How much protection does the prop shaft offer the engine? If I connect a copper wire from the zinc bolt closer to the shaft, would this protection increase? Trying to think of an alternative to removing the stuck bolt...

[S/V Illusion]

A prop zinc provides essentially no protection for the engine. Exaggeration for effect only - your perception everything is interconnected is true of all boats in the same ocean!

There is a well-documented distance in water only, typically of 5 ft or less, within which a zinc can provide some protection for salt water.

Drill or cut out the heat exchanger zinc.

[sailvayu]

The engine zincs protect the inside water jackets of the engine and inside the heat exchanger. Find a way to get them out and replace them annually.

Good luck

[KateJoy]

l work on a fuel dock, and have seen the damage not having all of your zincs can do to your engine. lt may be a pain to change out, but its much worse if you don't.

[never monday]

Originally Posted by sailvayu

The engine zincs protect the inside water jackets of the engine and inside the heat exchanger. Find a way to get them out and replace them annually.

Good luck

or replace the engine every 3-5 years :shrug: