On my 2005 H38 with Yanmar 3JH4E with Kanzaki gearbox there is an oil change nut on the port side of the gearbox. According to the manual there should be a copper washer in front of the nut. I never found it, maybe the PO lost it. I ordered it from Yanmar and received a copper washer of the wrong dimensions. I took things in my own hands and bought a piece of nitril rubber and cut a washer of the correct dimensions.
Conclusion: no need to suc the oil out of the Kazaki KM35P gearbox, just unscrew the nut, there is only 500cc of oil in the gearbox anyway.