After servicing my Yanmar 2GM changing oil, filters and belts, I noticed a leak on top of the injectors. After some research, I found that it is easy to replace the bolts and gaskets, and that removing them won't affect the injectors. It is a low pressure return pipe that ends open in the tank, so no high pressure involved. I also change the pipe.
These are the replacements pieces:
(qty) YanmarModel Description
(1) 105311-59500 Fuel return pipe
(2) 101147-59810 Bolt
(4) 23414-080000 Gasket
Here are some pictures: