Slight "screeching" warning buzzer

Benny17441 · Feb 13, 2018

One possibility; the wiring harness from engine to control panel is usually routed inside the hull around sharp fiberglass corners. In older boats with considerable hours of hull flexing that harness can start to chaff tearing away at its insulation and that of the wires inside. That harness carries power to the starter solenoid and to the warning lamps and buzzer. The first indications of a problem are usually with random faults with the warning lamps and/or the buzzer. Any chaff to the harness can usually be identified by visual inspection especially where the harness bends around a corner. Any cuts in the outer cover should be exposed to check and see if any of the inner wires could have lost their insulation also. it is that same hull flexing motion that makes the faults occur randomly. If left unattended and with enough time the chaff will eventually find the power wire and then the whole panel will go dead. Like I said this is just one possibility of various and not necessarily a most common one.

marchem · Feb 13, 2018

Clydo said:
With engine running at idle 1100 rpm have very very faint buzzing sound from oil pressure gauge. When at
about 1500 RPM have fairly loud "screeching" sounds from buzzer but only at about that rpm. Will
clean engine connections and check wiring at panel but anyone have this problem?
2003 C310 with M25XPC eng about 410 hours. Oil at proper level no leaks with
annual changes Eng does not use oil between changes (about 45 hours) Again noise only at those two rpm levels. Appreciate any thoughts.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

I had something similar happen. Because I’m a little OCD I installed an oil pressure sensor at the engine and a gauge at the control panel. I don’t see any drop in pressure and the alarm hasn’t happened again, for some unknown reason.

jssailem · Feb 14, 2018

@marchem Rob, Not OCD at all. Just a good solution to correcting a boat problem. The fact that the sound has not returned is evidence of the fact.

marchem · Feb 14, 2018

jssailem said:
@marchem Rob, Not OCD at all. Just a good solution to correcting a boat problem. The fact that the sound has not returned is evidence of the fact.

My wife would disagree with you about the OCD.

But I'm a lucky man because she loves to sail as much as I do, and she lets me do all sorts of boat projects.

jssailem · Feb 14, 2018

You are a lucky man Rob.. Remember it is Valentines Day...

LeslieTroyer · Feb 14, 2018

Harness replacement is on my todo list for next fall/winter. @marchem gauges are always better than idiot lights.

Mahalo

2 OLD PIRATES · Feb 14, 2018

Hi Clyde:
I have the 2003 C310 with M25XPB engine with 500+ hours and the same problem. I've been all over the engine and panel in the cockpit with no solutions yet.

It's enough to .............

If you find a resolve drop a line here.
Cheers
2 Old Pirates

marchem · Feb 14, 2018

2 OLD PIRATES said:
Hi Clyde:
I have the 2003 C310 with M25XPB engine with 500+ hours and the same problem. I've been all over the engine and panel in the cockpit with no solutions yet. It's enough to ............. If you find a resolve drop a line here.
Cheers
2 Old Pirates

Do you get the buzzer when you first turn the key on and before the engine starts? If so, the intermittent buzz with the engine running could be caused by low oil pressure, or a bad contact at the oil pressure switch that fails with engine vibration, or a failing oil pressure switch. Unless it happens consistently it will be tough to troubleshoot, because the circuit for the oil pressure switch on the M25XPB in most of the C310s is complicated. I'd be tempted to just replace the switch, or maybe temporarily short the two terminals at the switch together and see if the intermittent buzz stops. But be careful because you won't have anything monitoring your oil pressure when you do that. That's one advantage of having an actual gauge readout of the oil pressure.

marchem · Feb 15, 2018

Clydo said:
Did you use the same wire and just replaced oil pressure sensor and guage?

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

New wire and sensor. There’s a port already there that the new sensor screws into. I can look up the details, if you want.

marchem · Feb 15, 2018

Here's some info from a thread from this site that describes the circuit pretty well. Do be careful, because the M25XP is different from the M25XPB:

https://forums.sailboatowners.com/index.php?threads/oil-pressure-switch-on-universal-m25xpb.122118/

Here is the circuit: The oil pressure switch's closure is actually completing the circuit for power to the fuel pump when the engine is running and oil pressure is greater than 5psi. The presence of +12v also keeps the buzzer quiet and led off. If oil pressure is lost than the switch opens and removes power to the fuel pump, the low impedance of the fuel pump now provides a stiff enough ground to activate the buzzer and associated light. This all ties into the issue I posted earlier in the thread about the connector to the fuel pump corroding. It is really a very crafty way to solve two probelms with one circuit. Only thing is they're obvious intention to protect the motor in the case of a low oil pressure condition will not be effective if you have a full tank of gas, it will gravity feed is our installation. So, bottom line is make sure the buzzer sounds when you first turn the key on, because if it does not and you have a full tanks and loose oil pressure you will not know it because the alarms will not sound and the engine will keep on running.

valcour · Feb 15, 2018

If the buzzer is not loud and clear, replace it (cheap, easy troubleshooting). I had similar problem, and after a lot of checking with meter and head scratching, replacing the buzzer fixed the problem. You may have other issues, but the alarm is cheap.

https://forums.sailboatowners.com/index.php?threads/intermittent-oil-pressure-warning.183208/page-2

Tom J · Feb 18, 2018

Clyde, I have a 2003 C310, same engine. I had the same issue with the buzzer. I finally hooked up a pressure gauge, and pressure was normal. I found the terminals on the sending unit were loose. They are the push on type. I crimped them a bit with diagonal cutters, so that they pushed on much tighter. Then I used zip ties to hold the harness tight to the sending unit. Buzzing stopped. I also found later, when I replaced the alarm ( no buzzing when ignition was turned on) that Catalina had installed a 24 volt alarm. The replacement alarm from Catalina Direct was a 12 volt unit. The new alarm was much louder and more distinct than the old one.