I was just searching for a schematic of the harness between the 2GM and the instrument panel. A PDF version of the Yanmar manual was found online. Here is the link that may be useful to those interested: http://www.guillermo.ca/pdf/yanmar.pdf
Did you run across an updated manual at the site for a 2GMF. "F" I believe stands for Fresh water cooled which is what I have. These were put into some of the later model j30's.