It's a systemic problem. Attitude Adjustment 2 had an engine survey when she had about 400 hours on her eleven years ago. She has 2300 now. The oil pressure gauge was unhooked when I bought her. Pre-sale, I had an engine survey. He noted the non-working gauge and tested the oil pressure. He found it to me normal. After I got the boat, I purchased a new sending unit, However, it registered very low. So, sometime later, I got a new gauge. It still registered low. So, later yet, I got another sending unit, and it was defective out of the box. When I got a new one, nothing changed. Being concerned, I got a manual gauge and checked it. Yup, it was fine. So, I asked a Yanmar rep at a boat show, since the sending units and gauge were $100 a copy. He said go to a John Deer dealer. Well, I just sort of ignored it for a while and then tried some non-Yanmar sending units. Well, that was a disaster since the threads are not close to any standard here. I think they are metric NPT. Anyhow, I found an Izusu diesel sending unit had the same threads and got one, but it read in reverse. At this time, I just motor away and don't worry about it since the low pressure alarm works fine. The gauge just works as a go-no go idiot light. One day, I will have a different brass coupling made up and replace both the gauge and sending unit. Bottom line: I would have it tested with a mechanical gauge and WATCH it happen or do it yourself before worrying!
