Manuals, manuals .....
The actual yanmar manual is of very little use, being written in "Jinglish" Do yourself a big favor and get the Selden shop manual for the Yanmars. A wealth of information from people who KNOW the engines.2GM's started going into the 33's in around 1980. The 2GM is a considerably smaller, lighter engine and is VERY unlikely to be mistaken for the 2QM. Aside from the size of the engine itself, the gears were completely different. The QM required a lot of pressure to engage, thus a good size shift lever, while the GM can be flipped into gear with a pinkie and thus normaly uses a very small shift lever.