Oil Pressure Light on??? All seems OK?? Universal 25 XPAC

[mytime]

I have a Catalina 30 1994 Universal 25 XPAC with 900 hrs. Occasionally my oil pressure light would come on after hours of running at 2700 rpm and then I reduce my rpm to 750 and it would "beep" until Rpm's were raised to 800. This did not happen every time... 2 out of 10 times.

This past week we motored 12+ hours at 2700 rpm's over 2 days with no issues.
We motored out of Baltimore for 30+ minutes with no issues...put sails up for 5 hours and then turned the motor on to head back to marina.
Within 2 minutes of motoring the oil pressure alarm went off at 2500 rpm's...I shut it down checked oil and the stick was clean (no oil). Stuck it back in (no longer then 5 seconds have passed) and oil was full. Restarted motor ran it at 1200 Rpm's light came back on and same results I shut it down checked oil and the stick was clean (no oil). Stuck it back in (no longer then 5 seconds have passed) and oil was full.

We sailed for 30 minutes fired motor up and ran at 1500 Rpm's for 1.5 hours with no alarm and no noises in motor or temp issues.

This weekend I will be replacing the sending unit, change oil & filter and put an oil pressure gauge on.

My feeling is it has a bad sending unit or collapsed oil filter ...
BUT WHY NO OIL ON STICK WHEN I CHECK AFTER AN INCIDENCE?
Could it be a oil bypass valve that is bad?

Observations:
I looked into oil fill at valve cover and no debris (actually looks very clean!)
Oil does not smell like diesel

Sorry for all the details but I wanted to give the most accurate account of problem... Thanks for any advice or help!

 

[Ralph Johnstone]

Re: Oil Pressure Light on??? All seems OK?? Universal 25 XP

Your first step to analyzing the problem is to install the oil pressure gauge. This will tell volumes.

After that .......... do one change at a time to find out exactly where the problem lies.

When the engine is shut down, oil will lay in the upper portion of the engine and take a few minutes to drain down into the pan. Why your level change is so fast and extreme is a head scratcher.

Let us know where the problem lies when you have an answer.

 

[Stu Jackson]

BUT WHY NO OIL ON STICK WHEN I CHECK AFTER AN INCIDENCE?

It's simply because there is a seal on the end of the dipstick. You need to remove the stick, wait a moment, reinsert and check the level.

 

[mytime]

Re: Oil Pressure Light on??? All seems OK?? Universal 25 XP

Thanks Stu... I was not aware of that...Excuse my ignorance but If there is a seal how does it read correctly after I dip it again?

Ralph, I agree with you, however my timeline does not allow me to troubleshoot the problem piece by piece because the issue does not happen consistently. If I replace one item and I am 30 miles from home port and light comes on I am in a bad spot. We are weekend warriors and need to be in work on a Monday morning. I just need to make my problem go away. I will keep you updated.

 

[mytime]

Re: Oil Pressure Light on??? All seems OK?? Universal 25 XP

Stu, Never mind...You pull stick out fills tube up for measuring...put stick in and it locks out the tube...makes sense now. Never seen that before?

The schematic does not show a seal on the tube?? Is there something I'm missing?

 

[Capt jgw]

Re: Oil Pressure Light on??? All seems OK?? Universal 25 XP

The dip stick on my 5411 does that too. I always check it before starting, but of I just pull it out and look (like I do on my car), it's almost dry. Put it back in and check again, it's normal level. Must be the oil gets sucked out of the dip tube when you're running and the seal prevents it flowing back in. Break the seal first and you get the actual level reading. As old as my engine is I'm surprised the seal still works.
As for the oil light, it's probably the sender or it's wiring. You'll know for sure after you change it. If the lube pump was bad, you'd be having more problems. Like a seized engine.

 

[mytime]

Ok first round of troubleshooting: I went down to change sending unit and the one I purchased from Universal only had one terminal on it (pic2). The one on the boat had 2 terminals with 3 wires going to it (pic1).
1 wire appeared to be a standard oil pressure sensor wire (14 gauge?) to activate the light/buzzer. The other terminal had 2 heavier wires (10 or 12 gauge?). The 2 heavier wire set up appeared to be hot... it hit the block and sparked.

I put a manual oil pressure gauge on it started motor and the light came on..but good pressure on the gauge 35+lbs. This would indicate to me it is a bad sensor.

2 questions:
Where can I find the proper sending unit?
What are the 2 heavy gauge hot wires going to sensor?
I found a wiring schematic from the previous owner and it looked like the diagram pointed to the wires going to the lift pump...WHY?

I looked at another 1994 Catalina 30 and his setup was identical so I know it is not a aftermarket add on.