Drop in oil pressure

[BILLDON]

I have a 1999 Volvo Penta 5.0 Gi PEFS with about 475 hrs. Where I go on weekends, I sometimes run into a lot of Kelp seaweed floating around that blocks off the raw water intake on the drive, resulting in a gradual increase in temperature. This is nothing new. Yesterday, it happened again. I saw the temperature gauge going up and when it reached 200-210, I shut the engine off, raised the tilt and looked back there. By then all the kelp had washed off, which is also usually the case. I lowered the drive, and re-started the engine. The temperature slowly returned to normal. This happens a every once in a while. However, this time, the engine oil pressure, usually around 40 psi, did not return to normal. It stayed constant at just over 20 psi for the rest of the trip, about 12 miles. Everything about the trip was otherwise very normal. Engine ran and sounded no different. I am going to drain the oil today and see if there is any issue of contamination, etc. but I really think it might be the gauge or sender. Wondering if anyone has had this kind of issue before?

 

[ckoffend]

My good friend has a FourWinns boat with, I believe, the same exact engine (at least a V8 Volvo). He is constantly getting low oil pressure alarms and the problem is in his gauge. He has brought a mechanic on the boat with him and they have done in-line tests on the actual oil pressure, even when the gauge showed it dropping and then alarming. The actual oil pressure never changed. It was purely a gauge problem. My friend has told me that he must replace the whole gauge cluster and not just that oil pressure gauge - so he now runs with a wadded up cloth over the audible alarm so it isn't so annoying. Now, this isn't the engine, it is the gauge issue. But just thought I'd share that brief bit of information.