My 3GM30F has no zincs due to the heat exchanger material (Cu-Ni). I suspect your engine is the same.
After lots of reading in this any other places, I agree that the Yanmar 2GM20F (fresh water cooled- has antifreeze canister) indeed has NO zincs in it - due to the unique corrosion resistant alloy used in the heat exchanger (the only part of the engine to contact sea water). The 2GM20 (entirely sea(raw) water cooled) does have the pencil zincs since the sea water contacts various parts of the engine block during its cooling cycle.My 3GM30F has no zincs due to the heat exchanger material (Cu-Ni). I suspect your engine is the same.
I have been going nuts trying to locate the Zincs on my 2GM20F, your post is the first I have found that says there are none. But since the manual simply says they would be behind a cover labeled with a sticker that says "Anticorrosion Zincs" and no such sticker is on my 1988 engine, I'd say you are correct.After lots of reading in this any other places, I agree that the Yanmar 2GM20F (fresh water cooled- has antifreeze canister) indeed has NO zincs in it - due to the unique corrosion resistant alloy used in the heat exchanger (the only part of the engine to contact sea water). The 2GM20 (entirely sea(raw) water cooled) does have the pencil zincs since the sea water contacts various parts of the engine block during its cooling cycle.
I ran across this info during my research. . . There is a lot of controversy surrounding the proper use of zincs and electro galvanic corrosion in general and I encourage everyone to be aware that there is a huge difference in the high quality marine Bronze (which is copper+Tin alloy) through hulls and fittings and some BRASS (which is copper + Zinc alloy) thru hulls and fittings/ adapters being sold. Attaching a brass fitting to even an excellent bronze thru hull or valve creates a high potential for corrosion and catastrophic failure even if you electrically bond everything together. The Zinc in the alloy acts just like a zinc should !! Just sayin' -- know what is on or being put on your boat!