I'm winterizing my 5.7 Mercruiser which has freshwater cooling. The most
important part of this rather simple process seems to be removing two
drains on the manifold elbow things on each side of the engine and one
on the heat exchanger. The latter one has a pencil zinc, the other two
do not.

Would it be prudent to install pencil zinc anodes on those two also? The
other one corrodes pretty quickly in salt water and I'm taking this rig
to the Bahamas, where I don't want all that warm salt water to corrode
my cooling system. What could it hurt?

Capt. Jeff