My first thought was that your oil pressure switch may be failing...going resistive, for example. Might want to check that out.

This seems an odd problem. Can you offer any further description??? Anything else odd that relates to these conditions?

I experienced an equally odd problem involving the warning buzzer which took me a couple years(!) to troubleshoot, but it was a great day when I finally found the fault: a broken (ie, open) resistor. Engine vibration caused the resistor to fail. It was hidden beneath heat-shrink and it was a devil to troubleshoot.

Let me think on this for a few days. I'll be on the boat over the weekend and hope to have time to glance at the schematic then.

On our boat, which has a M35A so might be different, the buzzer has two tones. The low oil pressure one is an alternating tone, the overheat one is a steady tone. Our buzzer was bad, it would go on or not inconsistently and was giving the solid tone on the low oil pressure circuit. I changed both the oil pressure sending unit and the buzzer and that solved the problem.

Thank you for your replys.
Here is more on this subject.
I purchased this vessel about 2 months ago. During the sea trial while the brokers was on board I noticed that the buzzer was going on and off on its own while engine was running. I asked the brokers why I was hearing that. I believe he was more interested in making his sale so he ignored it.
When I pick-up the boat and got on the water - at Alameda Island channel - by the time I reached the north end of the channel - a distance of about one mile that I had to engine since I was in the no-go zone - the buzzer started to come on intermittently then finally stayed on, (oil pressure has pulsating tone, by saying steady on - means that it continued on-off without stop). I had no choice but to continue to run the engine at about 2000 RPM for another 1/4 of a mile until I cleared the channel and I was able to open the jib only and sail beam reach on starbird tack.
The admiral then noticed that the galley sole was covered with black oil. She went down to clean it up. Then we switched places and I went down to take the engine cover off and take a look. The bilge was full of oil and I started to slip and slide inside the sole. I though this was not a good time to trouble shoot this. I was going to sail into my marina as I had done many times with my 25 footer. Then I started to smell smoke. I though fire was immanent and I was not going to wait. I contacted the Coast Guard. They showed up and stayed with me while I sailed to the nearest Oyster point marina bout 3 miles. Then they delivered me to a side tie doc.
I discovered the source of the leak, it was oil pressure switch. I have replaced it since then with the correct Universal part that was listed in the manual.
Having a degree in electrical engineering has helped me to study and understand the wiring diagram. It was interesting to see that its contacts provide current to the Fuel Lift Pump. In looking at the wiring diagram you see that the switch contacts places a short across the buzzer (+ and P ). This means that it will make no sound when there is sufficient oil pressure. The only way that the buzzer will sound is if the switch is open. This could happen if the oil pump is failing to pumping enough oil.
Please see the PDF file I have included. According to this diagram I do not see a resistor. Can you tell me where you found the resistor - and if possible can you provide a photo.
Thanks again.
I will post a note when I find solve the problem.

Your PDF is too low resolution to follow clearly, but it did aid my memory a bit. Can you re-post the PDF here as a higher res file? The system accepts attachments up to about 310kb; your file is only 120kb, so you have room for a higher res PDF. If the system won't let you post a larger file, then please email the schematic PDF in full resolution to me at LCBrandt(at)coastpilot(dot)com. I will then post it in the Technical - Reference section of our website for future access by Members (capital M).

There is one other possible symptom you haven't mentioned: In my case, when beginning to start the engine, I turned the key to the 1 o'clock position (but not yet pushed the Start button). At this point the warning buzzer should be loud and continuous beeping. During the time my resistor was failed this warning buzzer was not able to be heard. Do you have that symptom also???

The resistor I found failed open due to vibration is the one coming off the terminal of the Preheat Solenoid. It appears very blurry in your PDF, but it is there. And it is located in my boat actually coming off that solenoid. It is a small 1/4 or 1/2 watt resistor that goes to ground. I don't remember the resistance. When I replaced this resistor, I soldered copper braid (that I scrounged from a short piece of coax) to each end of the resistor thinking that the braid would isolate the new resistor from engine vibration. Then I insulated the 12 volt end of the braid, of course.

Without having a high res schematic at hand and re-reading your post I don't have a 'feel' of whether this resistor could give you the symptoms you describe. I am going on past experience and 'hunch' here, thinking that any weird symptom involving the oil px warning buzzer might be related to that resistor failing. In my case the resistor lead broke, failing open.

As a side note: Would you click on the User CP link, upper left corner of this page, and set up an automated signature? It would be nice to have the name of the person we're trying to assist. Thanks.

I have a 1999 C36 MKII and I had a problem with the metal "tang" connector on the Oil Switch that the wire connector attaches to. It was cracked and broke off. As you noted a no electricity or connection to that switch will cause the Oil Pressure Alarm to go off

Not exactly what happened to your engine, but what I suspected was that your metal "tang" connector on the Oil Switch was cracked at the base but still "kind of" makes contact and that the vibration of the engine makes it connect and disconnect.

It has happened to a few of our vintage C36's - Broken or bent "metal "tang" connector on the Oil Switch. The Oil Switch on the M35B is close to the bottom of the engine base and I suspect Westerbeke had these engines sitting in something while in transit or shipping that bent the metal tangs and over time the vibration of the engine creates a bigger crack which eventually breaks leaving an open circuit (which will make the buzzer go off)

So what I think might have happened to your Oil Switch wasn't just a Metal Connector breaking but rather the whole Oil Switch got damaged.

Did you notice any physical damage to your Oil Switch you replaced that was leaking oil?

I have the same engine - M35B. As somebody wrote, when you turn the key on, the low oil pressure warning should sound until the engine fires up. In mine, sometimes it does and sometimes it doesn't. I never really thought about it because whenever I turn the engine off, the warning sounds until I switch the key off. Maybe I'm developing a similar problem. (My boat is a similar year also - 1998.)

John, when you kill the engine and just before you switch the key off the warning beeper should sound. It sounds - or should sound - on both occasions: on Start, and again after shutting down the engine with the T-handle.

On our boat, that warning beeper serves an important secondary function. Just about 3 microseconds of that beep sounding and the cats have instantly *disappeared* into their 'enroute cubby holes'. Then on shutdown, the engine stopped and the beeper again, and as soon as it's silent they know they can emerge and be civil once again.

I can not thank you enough gentlemen for your input - Larry and tsenator -you were both right.
If you would like to know how all this happened read the last section of this post.

[B]Problem fixed![/B]
tsenator - you were right on - meta terminal or the "tang" as you call it or/and the wire leading to it was broken. I cut about 6" off of both of the wires and soldered new wires with new connectors. Works.

Larry - I found the 1K 1/2Watt resistor near the 10A circuit breaker next to the glow plug solenoid. But it was not causing any problem. It already has wire pig tails on either side. I am not sure what the purpose of this resistor is. See my hand drawn diagram here. It appears that the resistor is provided to complete the current through the buzzer so that it may sound. But this is not true. The buzzer stops sounding only when you disconnect the fuel lift pump +ve wire, which means that if the fuel pump is defective the buzzer will not sound - when the ignition key is on and the engine is not running. The buzzer requires 24VDC instead of 12VDC - I do not know why 24 VDC was selected instead.
Wiring diagram - Here is a link to the manual. on page 98 you will find electrical diagrams. This is a good site to find parts list and manuals on PDF. [url]http://www.westerbeke.com/OnlineManuals/200554_M-25XPB_M35B_M40B_Technic...

[B]Last section of the post:[/B]
In the interest of making my second post not very long I left out some facts.
In viewing the photo I have uploaded - you will see that there are some additionl thick battery cable that was added.
If I can be a detective I suspect that the previous owner added a radar. Since the radar uses addtional power the owner found out that they could not start the engine after a day of sail. The boat yard advised them to add a dedicated start battery. This was added with another switch and was located in the port lazzarette. The cables were routed arround the fuel tank and bolted to the lug you see in the photo. I suspect that the installer was not carfull in working in this area and caused physical damage both to the oil pressure switch and nearby wires connected to it.
You were right that the buzzer would sound at certain RPM due to engine vibration. I was concerned that the fuel pump was getting pulsed DC current instead of the steady DC current that it expects. These pulses will damage the coil and eventially the lift pump motor.
Buzzer must sound just after the ignition switch is turned on. If it does not sound it may mean that the fuel lift pump is going bad or there is a loose connection. It must be fixed right a way.

See you soon again.
Thanks.

I've been reading the posts in this thread with great interest though my situation is somewhat different.

I had a a coolant hose develop a slow leak which let coolant escape resulting in an overheat condition. As soon as the sonalert sounded, I shutdown and discovered the problem. We were just out for a day sail so it was no problem to simply add some fresh water to the circulator system to get us back to our club. I replaced the hose and refilled the system with coolant. When I fired the engine up, I noticed the low oil pressure alarm going off (I don't have the optional oil pressure gauge) so I shut down immediately and started looking for a new issue. Not finding any oil related issues and not have a oil pressure gauge handy, I thought I would try a new oil pressure switch but I wasn't able to find one at a local automotive parts store so I put the suspect unit back in until I could get a replacement from Hanson's. Well, I fired the engine up to get the boat back to my mooring and the alarm never went off. Of course I'm going to put a test gauge on the engine but wondered if anyone had an opinion as to whether my brief overheat condition could have been related to this or just a crazing coincidence? I also notice that my low pressure doesn't always sound before starting the engine as someone else had mentioned earlier.

Thanks,
-skip

Skip, can you give us some info on your boat? Year, engine model, etc. Perhaps put it in your signature in your profile.

There are several different engines in these boats and even among the same engines there are wiring differences for various years. There are at least two, perhaps three, different wiring diagrams and configurations for the M35A I have seen.

WRT the oil pressure switch, if you replace a two pole unit with a one pole unit (as was done on our boat by a PO), it will totally disable the alarms (as was done on our boat by a PO) and put one's engine at great risk. The two pole ones don't seem to be common at auto parts stores, I ended up getting mine from a Universal dealer with attendant extra cost involved. But considering the cost of a new engine at around $10K, I figured $35 for a $5 part was OK.

Hi Bud,

Thanks for the reply! Obsession is a 1998 MK II (hull # 1669) with a M35B. It has the 2 pole style pressure switch and I have no intentions of replacing it with anything but the same equipment.

David H. (Skip) Ramsay Jr.
36 Heather Ln.
Stow, MA 01775
C 508-641-7547
Rear Commodore
[URL="http://savinhillyc.org"]Savin Hill Yacht Club[/URL]
[URL="http://www.panoramio.com/photo/16765730"]S/V Obsession 98 Cat36 MKII hull #1669[/URL]

On my earlier post above - Mistakenly I had assumed that the buzzer was sounding due to oil pressure circuit. I recently found the problem and it was due to a faulty water temperature alarm switch. I had noticed that the buzzer would not sound when the engine was cold - but within 5 minuits I would hear continuous buzzer on ( not intermittant indicating low oil pressure). This sound would be heard only at 1200 and 2000 RPM. I will be replacing this switch shortly - stay tuned for the result.
Question - the buzzer is rated at 24 VDC. Are yours also a 24 Volt buzzer? It seems that it sould be a 12 VDC since the batteries are at 12 V. It is hard to hear - so I may consider changing it aswell.

I have an intermittent problem with my oil pressure alarm. When turning on the key, I expect to hear the pulsing oil pressure alarm right away. After stopping the engine, I expect to hear the alarm after maybe 10 seconds. Lately, the alarm only sounds occasionally. From what I've read here, it looks like I'd better have a look at the oil pressure sensor?? Sounds like an intermittent connection??

I don't have the schematic, is it posted somewhere?

thanks as always!

Hi Gary - I have posted a simplifed diagram here on post #9 above. You can see it if you go back one page. I hope that helps.

Well - I replaced the water temp alarm switch. It did not solve the problem. I disconnected the alarm wire from the switch and placed a continuity tester on the witch to ground - the tester is a separate circuit that includes a soanalert and a 9 V battery in series. It produced the same buzzing sound. This confirms that the switch is vibrating and contacts are viberating and closing due to engine vibration.
Has anyone had this problem? Any solutions?

[quote=plaineolde;6374]I have an intermittent problem with my oil pressure alarm. When turning on the key, I expect to hear the pulsing oil pressure alarm right away. After stopping the engine, I expect to hear the alarm after maybe 10 seconds. Lately, the alarm only sounds occasionally. From what I've read here, it looks like I'd better have a look at the oil pressure sensor?? Sounds like an intermittent connection??

I don't have the schematic, is it posted somewhere?

thanks as always![/quote]

Gary, we had the same problem this spring when we started using the boat. I put a new buzzer on and it has worked perfectly since. I was pretty sure the buzzer was at fault since it was largely disintegrating on the exterior.

[quote=baysailor2000;6366]On my earlier post above - Mistakenly I had assumed that the buzzer was sounding due to oil pressure circuit. I recently found the problem and it was due to a faulty water temperature alarm switch. I had noticed that the buzzer would not sound when the engine was cold - but within 5 minuits I would hear continuous buzzer on ( not intermittant indicating low oil pressure). This sound would be heard only at 1200 and 2000 RPM. I will be replacing this switch shortly - stay tuned for the result.
Question - the buzzer is rated at 24 VDC. Are yours also a 24 Volt buzzer? It seems that it sould be a 12 VDC since the batteries are at 12 V. It is hard to hear - so I may consider changing it aswell.[/quote]

When I bought my new buzzer I asked the guy at Seaward about that 24 volt business and he said they are rated for something like 9 to 36 volts and are called a 24 volt unit but work fine with any voltage in that range. He told me either 12 or 24 volt will work. I replaced mine with 12 volt and it works fine, it was rated from 6 to 19 volts IIRC. The new 12 volt one is loud you will have no trouble hearing it over engine, wind and wave noise.

My original post of 06/10/2010 was about the buzzer that sounds at about 1300 RPM and 2000 RPM for some unknown reason and it does this when the engine warms up.
Today 05/13/2011 - I located the problem.
The buzzing was not due to any oil pressure problem. It was the high temperature water switch that was turning on the buzzer due to engine vibration. I had proven that by disconnecting the temp switch.
So the real problem was that the bracket that is connected to the upper portion of the alternator was very close to the area that the temp switch was installed. As the RPM increased the bracket would hit this metal area and vibrate the temp switch. The solution was to place 1/16" washer behind the spacer and move the bracket forward. No more buzzing. I hope this helps some one one day.

Thanks, Haro, for closing the loop on that problem and sharing the result.

The source of excessive  engine vibration was cracked alternator hinge bracket. It finally broke off the engine on a long day of using the engine. I replaced the bracket with the original bracket. The new bracket was heavily painted to prevent corrosion.  Since the alternator needed a reliable ground it could not be grounded well due to heavy paint inside the mounting hinge hole. As a result the alternator coil burned up. After replacing the alternator, I installed a #8 ground wire from alternator ground lug to the house battery shunt.