3gm30f oil pressure

[daletournier]

Hi, over the last 3 days I've experienced a intermittent oil pressure light/alarm coming on, very slowly at first then building. I motored 140nm over three days, first day really pushed engine along (2850rpm) for 8 hours straight, then on the 3rd day 16 hrs motoring at approx 2600 Rpm. Late in both days alarm started making its noise, at first very lightly ( no light ) and then gradually becoming louder until light come on. I would reduce rpm which would make alarm and light fully come on before disappearing. On the first day, after reducing rpm and light/alarm going away I increased rpm and it was fine for the rest of the day. Last day I would do the same only this time after sometime light/alarm would slowly start to come back on and Id have to repeat the process all over again. Engine temperature was fine and engine sounded good.
I've just reached Puerto Galera Philippines, I think the first step is to find a pressure gauge and test pressure.
Has anyone experienced this before? Yanmar 3gm30f 4100hrs.
Didn't get into Anchorage until midnight so as yet haven't put alot of thought into it, I'm hopeing that when I awake the forum has spun it's magic and the answer miraculously appears on my smart phone ( simple answer).
Thanks in advance, Dale.

[sailorchic34]

Two thoughts come to mind, Change the oil and oil filter and check that the oil bypass, located under the threaded bit the filter screws on to, is not sticking open. Could be a faulty alarm switch but a gauge will show the pressures better.

My 3gm30F runs at 58 psig when hot, and has for the last 1000 hours.

[daletournier]

Thanks, did a quick oil filter change 10.00 last night while underway, didn't fix it. Did not think of checking oil bypass, will do this afternoon. What I'm puzzled about is why on both occasions it happened after extended running? When I started this morning it was fine. Also the coming into the Anchorage at low rpm (3nm) it was fine. I'm hoping faulty switch but can't see how extended running would be related.

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