Mystery oil pressure

[Salty Hound]

I just got my 2004 Larson w/ a 3.0 Volvo penta i/o back from a major rebuild after the intake manifold rusted out and sea water got into the engine. I put it on muffs and she ran and sounded fine. Put her in the water and did a light cruise for 15 min then varied speed from mid to high for another 30 min. Then the alarm sounded and the oil pressure gauge on dash was at zero so I shut her down immediately. I opened the engine compartment and saw light smoke but couldn't find where it was coming from and heard some crackling. Checked the stick and it had just a drop on the end. I sat for about an hour and checked the stick again, now the stick read full???? So I started her up and the oil gauge was back to normal and no alarm. So I started to head back and 5 min later the alarms were going off but the oil pressure gauge was reading fine so I shut her down again. Checked the stick and was full still. I got towed back because I didn't want to risk any more damage. When I got back to the house I checked the stick and it was full. So I started to flush her and the alarms were going off right from the start but gauge was reading normal. So I shut her down. Just want to add that the temp gauge was running at normal temps the entire time.

Any suggestions on where to start?

 

[Bondo]

and heard some crackling

Ayuh,.... Welcome Aboard,.... Sounds more like it's Overheatin',....

Was the impeller replaced with the rebuild,..??

 

[Fishermark]

So I started to flush her and the alarms were going off right from the start but gauge was reading normal.

What alarm(s) were going off? It would be good to narrow down the specific alarm.

The no oil on the dip stick, and then having oil on the dipstick would worry me. Maybe you didn't push it down far enough the first time?

As Bondo mentions it sounds like it was overheating - with the light smoke and the crackling. Those are generally not good! Did you try putting your hand on the manifold to see if it was hot?

 

[Salty Hound]

Impeller was rebuilt during the rebuild. I didn't feel the manifold and I pretty sure that the stick was down all the way but I was pretty ticked and may have just not realized it. The alarms that were going off were the in the engine compartment and the dash alarm.

 

[Scott Danforth]

I'm going to go with caked oil returns in the head. Keeping all the oil from returning. Pull the valve cover and take a look.

 

[Salty Hound]

Alright, getting the boat back tomorrow. My mechanic said that it was a bad oil sensor and sending unit. The new unit stopped the alarms. He ran the boat on muffs and had no issues with the oil disappearing from the pan. He said that I could've had a miss reading when I checked it on the water. I'll have her out in a few days to see how she will run. Crossing my fingers.