Strange starting issue - anyone else experienced?

Apr 6, 2013
73
Catalina 310 Annapolis
I have an odd problem with my starter I wonder if anyone else has encountered before with their 310. I moved my boat to a new marina with a friend today on the Ches Bay. We got out a bit, raised our sails and shut the engine down then sailed to for a while. When we started the engine again (Universal M25XPB) it started up just fine. But now, when the key remains in the start position, an alarm sounds and stays on until you turn the key back to the off position - but with the engine still running. I can start the engine just fine but have to turn the key back to off to turn off the alarm. And that shuts down the gas guage and the battery guage but not the tach or the temperature guage. Have you ever heard of this? Can I run the engine safely with the key off?
 
Jan 4, 2006
3,907
Hunter 310 West Vancouver, B.C.
Can I run the engine safely with the key off?
That's exactly why we learned to NEVER shut off the ignition key until after the engine is shut down. If you do, you won't have any alarms .................... and that's just not good.

Any questions ?

In case you haven't figured it out yet, you MAY have a real alarm situation but you chose not to believe it. Why would you choose not to believe an alarm on your own boat :facepalm: ? They didn't believe they had an alarm at the Three Mile Island Nuclear Generating Station and they ignored that as well. How did that work out ?
 
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Oct 22, 2014
16,128
CAL 35 Cruiser moored EVERETT WA
But now, when the key remains in the start position, an alarm sounds and stays on
What is this alarm telling you?
  • Are you over heating?
  • Low oil pressure?
  • Alternator not working?
  • Just shouting for no reason?
Ok it has to be one of the first 3... Better to figure out which before you head out for any length of time. You may not get back.
 
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Apr 6, 2013
73
Catalina 310 Annapolis
It appears the culprit could be a loose connection on the oil pressure sending unit. Plenty of oil and no leak. No overheating issue. Going to have the alternator checked.
 
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Jan 4, 2006
3,907
Hunter 310 West Vancouver, B.C.
It appears the culprit could be a loose connection on the oil pressure sending unit.
No, if it were a loose connection the LO pressure alarm circuit would never sound. It's a normally closed switch (N.C. switch) which opens with pressure.

The alarm is sounding, therefore there are NO loose connections. What there may be is an accidental connection to ground.

OR the pressure switch (sending unit) is permanently closed because its diaphragm has a hole in it.

A multi-meter will give you the answer.
 
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Apr 6, 2013
73
Catalina 310 Annapolis
No, if it were a loose connection the LO pressure alarm circuit would never sound. It's a normally closed switch (N.C. switch) which opens with pressure.

The alarm is sounding, therefore there are NO loose connections. What there may be is an accidental connection to ground.

OR the pressure switch (sending unit) is permanently closed because its diaphragm has a hole in it.

A multi-meter will give you the answer.
 
Apr 6, 2013
73
Catalina 310 Annapolis
Thanks! I have a multi-meter and took an elementary sailboat electronics class but, hope this isn't a stupid question, but what would I test with the meter? I am a newbie to figuring out the diesel and electrical systems on my new to me boat but want to learn.
 
Jan 4, 2006
3,907
Hunter 310 West Vancouver, B.C.
I have a multi-meter and took an elementary sailboat electronics class
You're off to a good solid start.

what would I test with the meter?
The first thing to do is to disconnect the wire connected to the pressure switch. Next, turn on the ignition switch but don't start the engine. You should NOT hear an alarm if we're barking up the right tree. There is no way for the 12V current to get through the alarm because the circuit is disconnected. If the alarm still sounds, there is an accidental ground between the switch and the alarm. Think of it as the wire being stripped of its insulation and rubbing up against the engine. It's going to be dirty but that's the only way to find it.

For now, let's assume that the alarm did stop when the wire was disconnected. Next, with the wire removed from the pressure switch and the ignition off, measure the resistance across the switch. It should be "0" if everything is working.

Next, start the engine and again check the pressure switch resistance . You now have oil pressure. The resistance should be infinite showing the internal contacts are now open. This proves the switch works. If the resistance is still "0", the switch is broken and needs replacement.

If none of this proves out, there may be a problem with your oil pump (you have sufficient oil) and the alarm is telling you there actually is LO oil pressure.

Let us know what you find.
 
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Tom J

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Sep 30, 2008
2,004
Catalina 310 Quincy, MA
It appears the culprit could be a loose connection on the oil pressure sending unit. Plenty of oil and no leak. No overheating issue. Going to have the alternator checked.
Very common issue on the M25XPB. A loose connection at the oil pressure switch will set off the alarm. They are slide on connections, so you should at least crimp the loose one somewhat before sliding it on. At some point, it would be a good idea to switch to a screw type connection switch.
Always check to see why the alarm is sounding. When my oil alarm kept sounding intermittently, I bought an oil gauge that I can hook up to the engine to double check the pressure.
 
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Apr 6, 2013
73
Catalina 310 Annapolis
You're off to a good solid start.



The first thing to do is to disconnect the wire connected to the pressure switch. Next, turn on the ignition switch but don't start the engine. You should NOT hear an alarm if we're barking up the right tree. There is no way for the 12V current to get through the alarm because the circuit is disconnected. If the alarm still sounds, there is an accidental ground between the switch and the alarm. Think of it as the wire being stripped of its insulation and rubbing up against the engine. It's going to be dirty but that's the only way to find it.

For now, let's assume that the alarm did stop when the wire was disconnected. Next, with the wire removed from the pressure switch and the ignition off, measure the resistance across the switch. It should be "0" if everything is working.

Next, start the engine and again check the pressure switch resistance . You now have oil pressure. The resistance should be infinite showing the internal contacts are now open. This proves the switch works. If the resistance is still "0", the switch is broken and needs replacement.

If none of this proves out, there may be a problem with your oil pump (you have sufficient oil) and the alarm is telling you there actually is LO oil pressure.

Let us know what you find.
Thanks! I will.
 
Apr 6, 2013
73
Catalina 310 Annapolis
Very common issue on the M25XPB. A loose connection at the oil pressure switch will set off the alarm. They are slide on connections, so you should at least crimp the loose one somewhat before sliding it on. At some point, it would be a good idea to switch to a screw type connection switch.
Always check to see why the alarm is sounding. When my oil alarm kept sounding intermittently, I bought an oil gauge that I can hook up to the engine to double check the pressure.
Thanks!
 
Jan 4, 2006
3,907
Hunter 310 West Vancouver, B.C.
Very common issue on the M25XPB. A loose connection at the oil pressure switch will set off the alarm
Most unusual. According to Catalina Direct, it also shuts down the engine in the event of low oil pressure or switch failure which you don't mention.

Engine Stop.jpg


I can't help wonder if both you and the OP have a different type of pressure switch rather than the one recommended for the Universal M25XPB. Neither of you have problems with the engine shutting down and the switch only has TWO contacts. Maybe Catalina changed their mind because of the engine shut down problem.

I honestly don't know.
 

Tom J

.
Sep 30, 2008
2,004
Catalina 310 Quincy, MA
Most unusual. According to Catalina Direct, it also shuts down the engine in the event of low oil pressure or switch failure which you don't mention.

View attachment 194482

I can't help wonder if both you and the OP have a different type of pressure switch rather than the one recommended for the Universal M25XPB. Neither of you have problems with the engine shutting down and the switch only has TWO contacts. Maybe Catalina changed their mind because of the engine shut down problem.

I honestly don't know.
If I remember correctly, the M25XPB has an oil pressure switch, not a low oil pressure switch. When you hold the "ignition" key on, it provides power to the lift pump and silences the oil pressure alarm. When the engine develops enough oil pressure, the pressure switch provides power to the lift pump and silences the alarm. If the oil pressure drops, the lift pump shuts down the engine and the low oil pressure alarm is engaged. This is a normally open switch, not normally closed.
Unfortunately on the C310, the engine will often run without the lift pump working, since the fuel level is sometimes higher than the lift pump.
 
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Apr 6, 2013
73
Catalina 310 Annapolis
I am going to have a mechanic look at it just to confirm that is the issue and make sure there isn't something worse going on. Will share what he says. I am thinking I will add an oil gauge and sending unit because I would like a more accurate and sure way to know I have adequate oil pressure. I on the Catalina Direct site that many people put the gauge where the battery monitor gauge is now as there is also a battery gauge on the main panel.
 
Oct 22, 2014
16,128
CAL 35 Cruiser moored EVERETT WA
Top two battery gauges from our SBO Marine Electrical Engineer.


If you want to know amperage or energy into and out of the bank you'd need a battery monitor such as a Balmar SG200 or a Victron BMV series. An accurate digital volt meter, sensing directly at the battery terminals, can also be a good "bottom voltage" guide (12.2V).
 
Jan 4, 2006
3,907
Hunter 310 West Vancouver, B.C.
I am thinking I will add an oil gauge and sending unit because I would like a more accurate and sure way to know I have adequate oil pressure.
That will eliminate all head scratching as loss of oil pressure is the #1 destroyer of your engine. The presure gauge will answer a lot of questions immediately. With engine temperature, at least you've got a minute to consider what's going on.

Picture 022.jpg

Sender.JPG

The pressure sender is simple to install on the engine. Running the wiring can be a little more painstaking.

Keep us up to date.
 
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Nov 26, 2012
1,532
Hunter 34 Berkeley
That's exactly why we learned to NEVER shut off the ignition key until after the engine is shut down. If you do, you won't have any alarms .................... and that's just not good.

Any questions ?

In case you haven't figured it out yet, you MAY have a real alarm situation but you chose not to believe it. Why would you choose not to believe an alarm on your own boat :facepalm: ? They didn't believe they had an alarm at the Three Mile Island Nuclear Generating Station and they ignored that as well. How did that work out ?
Good God, Man! You could have blown us all to smithereens!