Head gaskets Require Sealant?
Yanmar head gaskets do not require any sealant. NEVER use silicone on a head gasket. You MAY use a coppercoat if you want but it is not required. Be sure both the head and the top of the block are completely clean & smooth.
link to copper coat--
http://www.scegaskets.com/K-W-Copper-Coat-p6650081.html