I've got the same boat (MS400 with twins, '05) and have a remote oil filter on the starboard engine. The lines run forward to the mount on the starboard stringer. If interested, I will get pic next time I'm at boat.
Remote filters can be mounted to a bracket on the engine as well if there's a good spot, they don't have to be on a bulkhead or anything.
Our remote filters are mounted on the engine itself. One engine, it's an oil filter; the other is fuel secondary and coolant.
Ours are Cummins, not Yanmar, but I'd have expected Yanmar has a solution like that too.
-Chris
I have a pair of Yanmar 4HLA and the port engine had the oil filter remoted to the port side. About a month ago, 2400 engine hours, the hose chaffed through and dumped most of the engine's oil into the bilge. The hose had a steel coil in it and a plastic chaffe guard on it. However it contacted the oil pan on both sides and wore through the guard and hose. I suggest insuring the hose don't contact anything. Repair options were to get new hoses or go back to the factory location. It will be a pain but I opted for getting rid of the remote setup.