1992 4.3 Mercruiser Oil Pressure

[JoeFromAkron]

While running last night my oil pressure switch started jumping, but only at low speed when I slowed down. It would go from just above 40 PSI (normal) to flat and jump right back up only when I slowed down. If I stayed at a higher RPM the pressure stayed up to normal. Luckily I wasn't to far from my marina. I got back to the dock and the oil was low, just barely showing on the tip of the dipstick, put in a quart but it still read low on the dipstick, about half through the "add" mark. Ran at dock, pressure stayed up just idling so I went back out and pressure stayed at 40 like it should. I only had one quart on board but Ill get another. All seems well.

Question is does anyone think I could have damage from this? There never was more than half a second that the gauge read low, it was just bouncing back and forth. I figure the oil pump wasn't getting oil momentarily? I didn't hear any funny noises or anything. When I went back to the dock I kept up speed as much as I could to maintain pressure and it did that until I hit idle speed. I'm just kinda nervous about this. Thanks for any assistance.

 

[TunaFish389]

Its hard to tell if damage was done. You were running bearing dry for a second. Best thing to do if you have a magnetic oil plug is check for shavings. Only way to be 100% is engine pull and specs bearing/shafts. But other than that just keep running and time will tell.

 

[JoeFromAkron]

Thanks. I guess I was hoping that I didn't do anything that would kill it immediately. I figured not but I've always had 2 stroke outboards so this motor is all new to me. Don't know about the drain plug. Only had the boat this season and the previous owner had the oil changed last year before winterizing so I didn't pay it much attention till now. lesson learned.

 

[Scott Danforth]

first, check your oil level
second, make sure its not a loose connection between the sender and gauge

 

[JoeFromAkron]

first, check your oil level
second, make sure its not a loose connection between the sender and gauge

Yes, oil is important. Lol Mildly concerned about why it was low but nothing was leaking. The sender has a light blue wire going to it, correct? The temp sensor was giving me trouble earlier this year and I think I remember that?

 

[Scott Danforth]

light blue for oil pressure, tan for water temp

 

[JoeFromAkron]

So i got a pump an removed most of what I put in, about 25 ounces. Oil was still showing a bit high on the dipstick after sitting and the oil pressure was fluctuating between 40 PSI and 10 while idling. It never did bottom out. Normally the gauge reads 40 PSI all the time. I added oil a few ounces at a time until the pressure quit fluctuating, less than 10 ounces. I'm beginning to wonder if I have the wrong dipstick for this motor or if they are normally that sensitive to the oil level? This is my first I/O.

 

[JoeFromAkron]

This turned out that I was just a moron. Weird thing about this motor is that the oil has always came out smeared on the dipstick even after sitting for days. I decided to just start over and do a full oil change. Well, I was only able to pump out a maybe a quart of oil. I was definitely getting to the bottom of the pan. Obviously that is no good but there was no metal shavings in it or anything like that. Filled with the correct amount and it is just amazing what a motor will do when it has the correct oil level. I'm surprised we didn't explode the thing, it seems to be fine somehow.