Low oil indicator fading in and out

[jonelli]

Had a weird thing happen today on way back. About 2/3 back from Catalina I heard a faint beeping. I recognized it as the low oil indicator. But the light wasn't on. Just faint beeps. I remembered when I checked oil before trip it was about halfway full on dip stick. So I added some oil underway. Beeping didnt stop then few min later came full on with light.
Stopped motor, checked oil, was totally full when stopped and dipstick didn't show any when running so I know oil is flowing.
No weird sounds or temp issues. After a little while it just faded away and never came on again.
I'm guessing bad sensor. If it was wiring I don't think it would fade in and out.
I haven't found the sensor yet. Would appreciate any pics of where it should be.
It’s a 87 MKII with M25XP motor.

 

[RoyS]

Are you sure it was the oil pressure light and not the charging voltage light? BTW, the oil light is reporting oil pressure and not low oil.

 

[jviss]

The alarm is for low oil pressure, not oil level, as @RoyS points out. You can have a full crankcase of oil and no or low oil pressure, which will eventually lead to serious engine damage.

One way to check is to connect a mechanical oil pressure gauge to the engine and see what it reads with the engine running. This can be connected where the electrical sensor currently is.

You might also be able to install an electrical pressure sensor if your current sender is just a switch, and have an electrical pressure gauge.

 

[jonelli]

Yes it was the oil pressure indicators for sure.
Aren’t those indicators normally full on or off? From what I learned it’s a pressure activated switch. Why would it fade on and off?
Are they NO/NC switches for our boats? Someone else mentioned to check the trailer wire plugs between the engine and the panel.
CD says their replacement switch is set for 7psi. Does that mean if I check with a manual gauge I should have something higher? What should it be normally?
If the dipstick is showing empty while running and full while stopped can I assume the pump is working properly?
according to the diagrams in the manuals, there is one wire going through the harness, correct? And that’s just a ground switch to the indicators?
I’d like to first rule out the switch somehow then move to verifying the actual pressure.

 

[Ward H]

Yes, the oil pressure switch is just that, a switch.
Most likely it’s the alarm circuit board going bad. That board is behind the cockpit engine panel and sounds the alarm for either low oil pressure or high engine temp.
The board on my boat went bad last season, having the same symptoms you are describing.
That board is no longer available. I replaced it with a new two tone buzzer. I bought it from Catalina Direct but I’m sure there are cheaper sources.
To retain the high temp alarm I installed a high temp switch in the thermostat housing. On my M25 XP there was a plug in a spare port next to the temperature sensor in the T housing. I believe I bought the switch from Amazon. The one from CD requires a funky connector.
If your engine doesn’t have the spare port you can drill and tap for one or buy the new t- stat housing kit from CD.
I connected the oil pressure switch wire to one side of the buzzer and the high temp alarm wire to the other side.
Now one tone of the buzzer is the high temp alarm, the other is the low oil pressure alarm.
Here’s a photo of the back side of my alarm board.

 

[jonelli]

Yes, the oil pressure switch is just that, a switch.
Most likely it’s the alarm circuit board going bad. That board is behind the cockpit engine panel and sounds the alarm for either low oil pressure or high engine temp.

Wow, didn't know there was that much complexity for the indicators. I figured it was just a sounder and light connected to the ground via the oil pressure switch. I don't know that mine has an alarm for high temp. At least I don't think so.

My panel looks like this: (not really mine, just online found pic)

 

[jonelli]

I don't know that mine has an alarm for high temp. At least I don't think so.

Found this on CD:
"
Temperature alarm on early boats
Boats built before 1990 had no temp alarm
"

 

[jssailem]

I would check the connections for the alarm and sensor. You could have corrosion on the terminals that is causing the fade in and out. The sensor may also be fouling, causing switch not to fully connect giving an partial or intermittent connection. It may be a little of everything.

 

[JoeWhite]

There is a 1000 ohm resistor in series with the soanalert that is located near the electric fuel pump. The stranded wires on each end tends to break due to engine vibration. That was the problem in my case. Check the electric wiring diagram. The oil pressure switch stops the electric pump in case there is no oil circulation to save the engine.

 

[jviss]

The oil pressure switch stops the electric pump in case there is no oil circulation to save the engine.

That's interesting. My Universal M25 in my Catalina 36 would run without the electric fuel pump!

 

[Ward H]

Found this on CD:
"
Temperature alarm on early boats
Boats built before 1990 had no temp alarm
"

Interesting. I thought all M25 XPs had the alarm board. Thanks for finding that.
I don’t think our vintage engines have the fuel pump interrupt circuitry that Joe ‘s 1999 boat has since when my key is on but engine is not running the low pressure alarm sounds and the fuel pump is still ticking.

I’d still look for corroded connections in the alarm circuit behind the engine panel.

 

[jonelli]

when my key is on but engine is not running the low pressure alarm sounds and the fuel pump is still ticking.

Mine is the same as you describe. I’m going to go through all that wiring as suggested.

 

[jonelli]

So far, I've tried replacing the oil pressure switch with a new one. No change.
Went on a long motor-sail last weekend, I could hear the sounder still faintly coming on once in a while randomly, so it wasn't that.
I have not yet had time to go through the wiring but I've been reading about it. Supposedly some of our boats use the fuel filter ground to connect to the oil pressure switch and that can be a problem. I'm not sure if mine is that way, but I've read most of the time what happens is that the failing connections at the fuel pump cause the pressure switch to never engage the sounder. That's what most people described.
I suppose something similar could be going on in my case.

I do have the trailer connectors in my boat, but I do not have the Ammeter at the control panel, so while I have the trailer plugs, I don't have the fire hazard design.

Talking out loud:
I plan on looking at my wire harness connections and will consider replacing the connectors or the entire harness, not sure yet.
I plan on inspecting the wiring if the oil switch goes through the fuel pump wiring or not, and if it does, to try bypassing it.
At some point, I have fried with a pressure gauge that I'll get over to the boat to do some verification.

Anything else I can try????

 

[jviss]

I wouldn't operate that engine until I verified that you have sufficient oil pressure. Then again, most like cause of low oil pressure is worn main bearings, so it might be toast anyway.

 

[JoeWhite]

Janelle to confirm the problem is due to sensor circuit, disconnect the 2 wires from the sensor and short them together or leave them open, I can not remember if high pressure opens or closes the contacts. Then run the engine and wait for the fading sound.

 

[mikeracca]

So far, I've tried replacing the oil pressure switch with a new one. No change.
Went on a long motor-sail last weekend, I could hear the sounder still faintly coming on once in a while randomly, so it wasn't that.
I have not yet had time to go through the wiring but I've been reading about it. Supposedly some of our boats use the fuel filter ground to connect to the oil pressure switch and that can be a problem. I'm not sure if mine is that way, but I've read most of the time what happens is that the failing connections at the fuel pump cause the pressure switch to never engage the sounder. That's what most people described.
I suppose something similar could be going on in my case.

I do have the trailer connectors in my boat, but I do not have the Ammeter at the control panel, so while I have the trailer plugs, I don't have the fire hazard design.

Talking out loud:
I plan on looking at my wire harness connections and will consider replacing the connectors or the entire harness, not sure yet.
I plan on inspecting the wiring if the oil switch goes through the fuel pump wiring or not, and if it does, to try bypassing it.
At some point, I have fried with a pressure gauge that I'll get over to the boat to do some verification.

Anything else I can try????

So after finding out how Catalina grounded the batteries together and also how this isn’t a great way to do it, I solved the ground problem by making a common ground bus (Blue Sea Systems 4 pole bus bar). Both battery banks ground to this bar, and from here the grounds for the charger, engine and the rest of the electrical system branch off of. This will be a major improvement over the house batteries grounded to the fuel filter, the starting battery to the bell housing along with all the minor circuit grounds as well.

One thing you want to prevent is making a ground loop. More grounds sound good right? Well wrong, a ground loop can cause things to act wonky, breakers that don’t trip when they are supposed to and even assist in producing galvanic corrosion. You want your grounds to only have ONE way back to the source in ALL circuits.

 

[jonelli]

So, good news… my oil pump isn’t bad.
bad news is I have a new wiring project.
pressure at full cruising rpm and idle both stable at full temp.

and while the pressure switch was out and the wire not touching anything, I could still hear the faint beeps from the sounder. When we touched the wire to the engine, it went loud and the light comes on as expected. At this point I’m assuming the multi pin trailer harness is the problem. It’s cracked on both connectors at the engine side and looks like crap. My first step will be to get rid of that and replace it with a waterproof terminal block housing then see if everything is cleared up. At least now I know for certain the engine is okay.

 

[mikeracca]

So, good news… my oil pump isn’t bad.
bad news is I have a new wiring project.
pressure at full cruising rpm and idle both stable at full temp.View attachment 206899View attachment 206900
and while the pressure switch was out and the wire not touching anything, I could still hear the faint beeps from the sounder. When we touched the wire to the engine, it went loud and the light comes on as expected. At this point I’m assuming the multi pin trailer harness is the problem. It’s cracked on both connectors at the engine side and looks like crap. My first step will be to get rid of that and replace it with a waterproof terminal block housing then see if everything is cleared up. At least now I know for certain the engine is okay.

If your lazzarette stays dry you could go with Anderson Power Pole connections. If you use the authentic ones from Powerwerx they are silver coated which is good in a marine environment, even silver oxide is a good conductor. They are easy to build, and they have terminals That can handle up to 45 amps. I usually use the 30 amp terminals for most of my stuff.

Here is my engine harness on the panel side.

 

[Stu Jackson]

@jonelli

Many of us have been "harping" on those trailer connectors for years. Surprised you hadn't gotten the memo.

Here's some other stuff you should be aware of, too, applicable to your boat with identical systems to our C34 boats:

Critical Upgrades http://c34.org/bbs/index.php/topic,5078.0.html

 

[jonelli]

@jonelli

Many of us have been "harping" on those trailer connectors for years. Surprised you hadn't gotten the memo.

Here's some other stuff you should be aware of, too, applicable to your boat with identical systems to our C34 boats:

Critical Upgrades CRITICAL UPGRADES - DO THESE OR ELSE!!!

Hey Stu, yah, I hadn't really had any issues with it till now, and most of the warnings on the common critical issues were pointing to things I didn't have. I have the late 87 mkII with M25XP. I don't have the Ammeter setup, the oil sensor isn't through the fuel pump, the alternator bracket is on it's own bracket like the upgrade kit, and I've already upgraded the main charging system wiring. I'm not sure about the traveler through-bolts though. I'll have to check next time I'm at the boat.
For now, I'm going to replace the engine compartment connectors with this: