Hi everybody. First sorrey about my english language. I have a problem oil pressure on mitsubishi s6r engin at 700 rpm is showing 5 - 6 bar thats ok. But when rpm go up to 8 - 8.5 the gauge starts to move up and down ( jumping) filters changed 80 hrs ago . Level ok. Oil needed to bee changed 300 hrs ago but not done. I suspect that this is the sensors fault, bu not shore. Any advice ?? Thanks a lot.

Remove the oil pressure sensor, screw an adaptor fitting with a manual oilpressure gauge attached and read the exact oilpressure throught all load / temp./ rev ranges.
In other words bypass sensor/sender/ loom and electronic display gauge.
It's called going back in time to how oilpressure used to be displayed.
Sometimes old ways are the best ways.

Thanks Merlyn! But the problem is that i dont have a manual oil pressure gauge.And at the moment the engine cant be stoped. Its the main engine. I am almost shore that its the sensors fault. But what else could cause fluctuation like this?. Thanks in advance.

Look up the necessary ohms meter readings for that exact sensor and measure it to see if it is within top/ bottom limits.
You'll have to heave to if you are a one engine jobby though.
Fluctuations sound like possibly the sender / sensor unit as I have always found a worn rear main normally controlling the oil pressure depicts a constant low reading and only increases with applying more revs.and on tickover when hot brings on the warning light on the control panel.
Manual test kits with adaptors are cheap as chips nowadays but make sure you have the correct screwed adaptor in the kit.
Sender units are also cheap so sometimes you may feel that unless the kit comes in for other jobs it's not worth buying it and it's maybe better to get another sender.
Best of luck!

Thanks a lot.

Seem to remember the oil pressure switch/sender unit is not screwed directly into an oilway in the side of the block but is sat on a bracket bolted onto the side of the engine fed by an armoured flexy hose which is screwed into an adaptor in the block oilway.
Normally a three wirer connection so by looking up the resistance readings depicted for the exact model sender you may well be able to monitor the readings to see if they are not constant at a fixed rpm i.e. fluctuations in the ohms readings depicting perhaps a faulty unit.
Should be an audible/shutdown alarm fitted to monitor the oilpressure.
I found this type of engine was normally associated with a tug or anchor/ rig attendant ship?

Thsnks Merlyn for your advice. It was the sending unit givng the fluctuation. This ship was a trawler. But now operating as a guard vessel.

Good one.
But dare I ask, Sussed or Substitution method here?
Hope your guard vessel duties doesn't encompass incoming rounds?

Sorrey for the late replay. Like you advised I checked the resistance and it was outside of normal parametrs. No didnt encompass incoming rounds. Everything was fine.
Thankyou!