I'm in VA still, I plan on sailing back up to Pier 3 (if there's still a slip) once I get this engine alarm handled. I will fall back to Pier 5 if needed but they are expensive and the draft is super shallow - plus 90% of the boats in there are ghost ships, it's creepy.
Welcome to sailing! Here, have an engine/electrical issue.
- Thread starter ethanknox
- Start date
I want to say I think the cooling is ok, just by deduction - I'm still getting the same amount of exhaust water flow as before all this, and the water temperature light has not gone on. Also other "duck quacks":
- the oil pressure light is on when the alarm is sounding
- the oil pressure light/alarm goes on when you turn the key (as expected, no pressure yet) and stays on when started/running (not expected, it appears there is oil pressure). There's no window where the cold engine gets warm, then too hot - it is immediate.
- If I disconnect the oil pressure sender from the wiring, with the engine off it reads a continuity of 0 with the block (fully grounded). When the engine starts, that reading climbs slowly (a few seconds) to 1 (fully resisted, no circuit). If I turn off the engine it immediately drops back down to 0. The whole time, the sender wire itself has a reading of 0 (fully grounded) and that makes no sense to me - if the alarm/light should be getting ground from the sender (ie allowing the sender to determine when the alarm/light trips) then the lead should always read 1 (no circuit) on its own.
- When I swapped the oil sender out and started the engine, the alarm stopped for the entire time I had it running, probably 2 minutes. Once I stopped the engine and started it again, the alarm immediately started again. It would be a weird coincidence for the alarm to be temperature-related at that point, since I started the engine probably 20 times last week and the alarm stayed on from start every time except the one time I had just changed the oil pressure sender unit - it feels more likely that I had wiggled the shorted wire somehow in the install process, bought myself one happy run, and then things went back to bad.
But I do struggle with why the oil alarm went off right after we came off the sand. I keep thinking that the motor revving and the jarring might have shaken something loose, but yeah cooling issue makes much more sense in that case, sucking something up. I guess if a) the ground diode in the temp alarm went bad it would leak over to the ground on the oil pressure, and b) if the lamp for the temp light were also bad I would only see an oil pressure light. but that leads to more questions:
- Would something in the raw water intake cause the alarm to go off immediately (maybe if there's a blockage?)
- How am I still getting water glugs out the back? could it be way less flow and I don't have the reference to know the difference?
- What about the alarm sputtering out/stopping, usually when I'm in reverse? how does that make any sense?
I'm going to try checking the strainer (not super easy to get to in this setup, otherwise I'd have already done it), then disconnecting the temp sensor to see if that stops the alarm. From there, I'll try running all the leads up to the panel connector directly and skip the wire harness to eliminate that from the equation. If that doesn't point out the issue, it's probably time to sink the boat and go live in a tent in the woods.
- the oil pressure light is on when the alarm is sounding
- the oil pressure light/alarm goes on when you turn the key (as expected, no pressure yet) and stays on when started/running (not expected, it appears there is oil pressure). There's no window where the cold engine gets warm, then too hot - it is immediate.
- If I disconnect the oil pressure sender from the wiring, with the engine off it reads a continuity of 0 with the block (fully grounded). When the engine starts, that reading climbs slowly (a few seconds) to 1 (fully resisted, no circuit). If I turn off the engine it immediately drops back down to 0. The whole time, the sender wire itself has a reading of 0 (fully grounded) and that makes no sense to me - if the alarm/light should be getting ground from the sender (ie allowing the sender to determine when the alarm/light trips) then the lead should always read 1 (no circuit) on its own.
- When I swapped the oil sender out and started the engine, the alarm stopped for the entire time I had it running, probably 2 minutes. Once I stopped the engine and started it again, the alarm immediately started again. It would be a weird coincidence for the alarm to be temperature-related at that point, since I started the engine probably 20 times last week and the alarm stayed on from start every time except the one time I had just changed the oil pressure sender unit - it feels more likely that I had wiggled the shorted wire somehow in the install process, bought myself one happy run, and then things went back to bad.
But I do struggle with why the oil alarm went off right after we came off the sand. I keep thinking that the motor revving and the jarring might have shaken something loose, but yeah cooling issue makes much more sense in that case, sucking something up. I guess if a) the ground diode in the temp alarm went bad it would leak over to the ground on the oil pressure, and b) if the lamp for the temp light were also bad I would only see an oil pressure light. but that leads to more questions:
- Would something in the raw water intake cause the alarm to go off immediately (maybe if there's a blockage?)
- How am I still getting water glugs out the back? could it be way less flow and I don't have the reference to know the difference?
- What about the alarm sputtering out/stopping, usually when I'm in reverse? how does that make any sense?
I'm going to try checking the strainer (not super easy to get to in this setup, otherwise I'd have already done it), then disconnecting the temp sensor to see if that stops the alarm. From there, I'll try running all the leads up to the panel connector directly and skip the wire harness to eliminate that from the equation. If that doesn't point out the issue, it's probably time to sink the boat and go live in a tent in the woods.
I am not sure this is the case with this yanmar diesel? I can start and run the motor forever with the alarm going off, the only way to cut the fuel is a manual cable pull (which is how you stop the engine since it is a diesel). The pump is mechanical. And the sender is normally closed (continuity with ground) when the pressure is 0, then opens as the pressure rises - this is why in normal conditions the alarm goes on when you turn the key but have not started the motor yet (it has power and no oil pressure) and goes off once the pressure opens the circuit.
I think you are way overcomplicating this. At this point I suspect a bad wire, the oil pressure switch sender wire getting grounded somehow.
So, we've established you have a normally closed switch, that opens with pressure.
By "fully resisted" you mean 'open circuit.' That means you have sufficient oil pressure.
As it should, makes sense; pressure drops, switch closes.
Where are you measuring this, and under what conditions? Is it disconnected from the sensor and you're measuring the end that would normally connect to the sensor?
I think that's correct.
Thank you for reminding me to look for the duck (when you hear quacking). I'm gonna go find that bad wire.
I'm interested in learning more about your setup.
I had a 1984 C36 with a Universal M25. It would run without the electric fuel pump running, so dropping power to the electric pump won't necessarily stop the engine. And, my fuel pump was energized by the engine panel key switch, and didn't go through any oil pressure switch. I'm pretty sure my oil pressure "switch" was a sensor for the oil pressure gauge and the alarm was simply piggy-backed to that, and sounded when the sensor approached ground - like, 10Ω when there was no pressure. Once it came up there was insufficient current to run the buzzer. Same with the coolant temp sensor, which goes the opposite way, low resistance at high temperature.
On the OP's boat I think we've established his switch, or sensor, is at low resistance, i.e., virtually ground, with no oil pressure, and the resistance increases with increased oil pressure.
Jviss, here is a link to my website that includes the wiring diagram to explain how it works.
Oil Pressure Switch | Sail La Vie
Also click on the link on this posting to read more on C36 international website regarding this same problem. All boat wiring may not be the same.
Oil Pressure Switch | Sail La Vie
Also click on the link on this posting to read more on C36 international website regarding this same problem. All boat wiring may not be the same.
That's not how my 1984 ("Mk. I") was wired. I had a sender to a gauge, and it energized the buzzer when it was close to zero Ohms (i.e., ~10Ω). And, my lift pump was wired directly to the keyswitch, as with key "ON," the pump operated. But, as I said, the engine would start and run without the lift pump. I know because mine was dead for a year without me realizing it. 
It sounds like most of what I would say has been said already. But, I will break it down a little differently. Here's how I would tackle this:
This just feels like a bad sensor/switch to me. In my engine, I have an OP sender to inform the gauge and a separate OP switch for the alarm. This gives me a way to troubleshoot since, if the alarm is going off, I can double-check the pressure gauge, and vice versa. If you have no gauge and/or you do not have a sending unit separate from the OP switch, the only way to really know what you're chasing is to manually measure the OP directly.
- Get an oil pressure testing kit (about $25).
- Test your ACTUAL oil pressure. If it is actually low, then you are chasing ghosts looking at wiring and sensors/switches.
- If it is not low, test the sensor/switch with a multimeter to see if it is doing its job. If it is, your problem is either wiring or the alarm itself. If it is not, then there's your problem.
This just feels like a bad sensor/switch to me. In my engine, I have an OP sender to inform the gauge and a separate OP switch for the alarm. This gives me a way to troubleshoot since, if the alarm is going off, I can double-check the pressure gauge, and vice versa. If you have no gauge and/or you do not have a sending unit separate from the OP switch, the only way to really know what you're chasing is to manually measure the OP directly.
I should probably get a mechanical gauge to rule out a pressure issue completely. I did already replace the sensor, and the new one does show climbing resistance via multimeter (I am sure I could look up what the yanmar sender resistance readings translate into and get a numeric pressure reading from it, but I just was happy to see it go from zero to non-zero, that may be a mistake).
I considered getting a "dual station" sender replacement so it could power an alarm AND a gauge at the same time, but that seemed like more variables and, given what I thought I knew at that moment (disconnecting the sender worked one time) it seemed like just replacing the sender would have done the trick.
This is eerily similar to an issue I am dealing with on the boat we just bought. It has a sporadic low OP alarm that just sort of randomly comes and goes. But, the OP gauge always registers normal. My initial thought was a wiring fault that was sometimes shorting out - depending on the vibration of the engine, wave action, etc. The way it comes and goes just "sounds like" a loose wire.
Going back a bit, just before we closed on this boat, the previous owner wired in a manual switch to turn on/off the fuel lifting pump. (Don't get me started on why he did this - that's a whole other story.) So, on our first few shakedowns with the new boat, I just got in the habit of manually turning on the lifting pump. We also started to notice this random alarm that seemed, by all indications, to be false. So, on our last couple of shakedown outings, I just turned the key off, which also turned the alarm off (and gauges). I preferred to turn the key on every so often, check the gauges, and turn it back off. This was better than listening to the alarm.
As we prepared the boat for the 4-day sail up to our home port, one of the things I did was correctly wire in the lifting pump so that it turned on when the key was on - per the schematics. Coincidentally, the alarm didn't sound after that. So, I chalked it up to some weird wiring issue that I either accidentally resolved, or that I would not be able to replicate. All gauges functioned normally and I manually checked the OP - all good.
About halfway up on our shuttle trip, the alarm came back. I lived with it for a while, but finally grew weary of it and just shut the key off. Blissful silence. But, after about 30 seconds, the engine sputtered and died. Of course, I had forgotten that I had wired the lifting pump in so it would not function with the key off. It took me an uncomfortable minute to recall this. But, I turned the key on, fired it up, and all was fine - except the occasional beeping.
This was such a source of stress that I finally just disconnected the OP wire from the alarm. Of course, this meant that the alarm would not sound even if the OP actually dropped. But, I was having to look at the gauge every few minutes anyway. This way, I didn't need to also listen to the alarm. And, the high-temp alarm would still work.
Anyway, all this to say that what I finally did was order a new alarm buzzer. Mine has two inputs terminals - one for solid tone (high temp) and one for pulsing tone (low OP). I had no reason to necessarily suspect the buzzer, but it was $30 to find out. Worst case, I have a spare buzzer. If that's not it, I will buy a new OP switch - another $30. I much prefer this approach to trying to track down gremlins. I will rule out these two pieces of hardware before spending a bunch of time looking for a wiring fault or doing any kind of in-depth troubleshooting. Yes, it's kind of throwing money at the problem instead of just doing a little basic legwork.
But, since I already ruled out ACTUAL low OP, I am not worried. Maybe I end up with a couple of spare parts and STILL have to crawl down there and chase an elusive short. But, I would rather pay a few bucks to create the chance of not needing to. I get enjoyment from a lot of boat maintenance tasks, but that isn't one of them.
Going back a bit, just before we closed on this boat, the previous owner wired in a manual switch to turn on/off the fuel lifting pump. (Don't get me started on why he did this - that's a whole other story.) So, on our first few shakedowns with the new boat, I just got in the habit of manually turning on the lifting pump. We also started to notice this random alarm that seemed, by all indications, to be false. So, on our last couple of shakedown outings, I just turned the key off, which also turned the alarm off (and gauges). I preferred to turn the key on every so often, check the gauges, and turn it back off. This was better than listening to the alarm.
As we prepared the boat for the 4-day sail up to our home port, one of the things I did was correctly wire in the lifting pump so that it turned on when the key was on - per the schematics. Coincidentally, the alarm didn't sound after that. So, I chalked it up to some weird wiring issue that I either accidentally resolved, or that I would not be able to replicate. All gauges functioned normally and I manually checked the OP - all good.
About halfway up on our shuttle trip, the alarm came back. I lived with it for a while, but finally grew weary of it and just shut the key off. Blissful silence. But, after about 30 seconds, the engine sputtered and died. Of course, I had forgotten that I had wired the lifting pump in so it would not function with the key off. It took me an uncomfortable minute to recall this. But, I turned the key on, fired it up, and all was fine - except the occasional beeping.
This was such a source of stress that I finally just disconnected the OP wire from the alarm. Of course, this meant that the alarm would not sound even if the OP actually dropped. But, I was having to look at the gauge every few minutes anyway. This way, I didn't need to also listen to the alarm. And, the high-temp alarm would still work.
Anyway, all this to say that what I finally did was order a new alarm buzzer. Mine has two inputs terminals - one for solid tone (high temp) and one for pulsing tone (low OP). I had no reason to necessarily suspect the buzzer, but it was $30 to find out. Worst case, I have a spare buzzer. If that's not it, I will buy a new OP switch - another $30. I much prefer this approach to trying to track down gremlins. I will rule out these two pieces of hardware before spending a bunch of time looking for a wiring fault or doing any kind of in-depth troubleshooting. Yes, it's kind of throwing money at the problem instead of just doing a little basic legwork.
But, since I already ruled out ACTUAL low OP, I am not worried. Maybe I end up with a couple of spare parts and STILL have to crawl down there and chase an elusive short. But, I would rather pay a few bucks to create the chance of not needing to. I get enjoyment from a lot of boat maintenance tasks, but that isn't one of them.
This has been bothering me, so I checked on what I have on my current boat, which is a Westerbeke 38B-FOUR with the Admiral panel.
I have and oil pressure switch and an oil pressure sensor. I also have a coolant temperature switch and a coolant temperature sensor.
From the schematic it appears the oil pressure switch is open at low pressure, and closes when the pressure comes up. It also appears the coolant switch closes at high temperature.
So, I may have been been wrong about the original poster's wiring. I have to go back and review, 'though I think I was correct from a logical perspective.
I have and oil pressure switch and an oil pressure sensor. I also have a coolant temperature switch and a coolant temperature sensor.
From the schematic it appears the oil pressure switch is open at low pressure, and closes when the pressure comes up. It also appears the coolant switch closes at high temperature.
So, I may have been been wrong about the original poster's wiring. I have to go back and review, 'though I think I was correct from a logical perspective.
So today I learned that with boats, when you hear hooves think "bald eagle carrying coconuts."
I climbed back to the raw water strainer (which is no easy task, otherwise I would have done this sooner) and found a thin layer of silt and grass at the bottom of the container. I wiped that out, fired the motor up, and... no alarm. I tried repeatedly, let her run, revved up RPMs, changed gears, but still no issues.
I guess that since the alarms share a common ground with inline diodes on each one, the diode on the water temp sensor must have gone bad and the alarm is leaking over to the oil pressure light. This means I no longer have distinct oil pressure, water temp, and charge lights, I have a screaming baby "something is wrong" alarm - which I am fine with. I also discovered that my multimeter has gone bad, so who knows what readings were actually correct this whole time
So I have a working boat again! I also got the charge inverter working and moved the pressure water off the AGM engine batteries to the lithium house bank today. It was a good day.
Thank you, everyone, for the feedback and help, I probably would have wrestled with ghost volts for another month without the ideas that this thread stirred up.
I climbed back to the raw water strainer (which is no easy task, otherwise I would have done this sooner) and found a thin layer of silt and grass at the bottom of the container. I wiped that out, fired the motor up, and... no alarm. I tried repeatedly, let her run, revved up RPMs, changed gears, but still no issues.
I guess that since the alarms share a common ground with inline diodes on each one, the diode on the water temp sensor must have gone bad and the alarm is leaking over to the oil pressure light. This means I no longer have distinct oil pressure, water temp, and charge lights, I have a screaming baby "something is wrong" alarm - which I am fine with. I also discovered that my multimeter has gone bad, so who knows what readings were actually correct this whole time
So I have a working boat again! I also got the charge inverter working and moved the pressure water off the AGM engine batteries to the lithium house bank today. It was a good day.
Thank you, everyone, for the feedback and help, I probably would have wrestled with ghost volts for another month without the ideas that this thread stirred up.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 21,608
When I needed to examine the water strainer on my boat the first time, I discovered it nearly impossible. Instantly, moving the strainer to a location that would be easy to service moved to the head of my priority list. Lack of water to cool the engine is an excellent way to extract big bucks from your wallet.
I think if I even added a 2” spacer between the strainer and where it’s secured to a stringer, that would do the job. Currently it’s under and behind the access panel so there’s not enough space to rotate your wrist around or get a wrench on the basket nuts. That might be my now fix, adding enough buffer to make it unpleasant but not borderline impossible to check. My hands and wrists look like I tried to bathe a stray cat from all the jagged snipped zip-tie ends that have brittled over time into razors and the oversized screw tips. Any nuts, washers, bolts etc you drop go directly into the black hole bilge under the transmission, never to be seen again. So yeah, it’s not great access at the moment.