Yanmar Water Warning Light / Buzzer

[Northeaster]

Jack - a mechanic could give you better advice, but here's my opinion. You need to check the manual to find the correct pipe and thread size for the water sensor. I did mine last year, but it was something like 3/8"x18npt (national pipe thread - 18 is the thread count). Now my Yanmar book said the engine temp sensor, and therefore the female hole it trheads in to, was (for instance) 3/8"x19npt. Well, 19npt is not a common trhead, so I had to buy 3/8"x18 npt. That means it will croos thread somewhat as it si threaded in. I am not recommending to use the wrong thread type, but I asked my mechanic, and he said it would be fine. YOu put teflon tape on it anyway, and mine has never leaked. So I bought a 3/8"x18npt tee, threaded it into the female 3/8"x19npt hole, where the old sensor was. Then I installed the old 3/8"x19npt sensor, as well as the new 3/8"x18 sensor, into the 2 female holes in the tee.

If the new temp sensor is not teh same size as teh old one, or the tee, you can get adapters, ie to from 3/8" to 1/4".

The new sensor / guage can be electrical, or analog??. which means one will have a fixed length cable that yo ucanb't cut - teh other type you may be able to cut and lengthen, but I am not sure about that. I bought one with about a 6 ft wire, connecting the sensor and gauge, which was long enough to get to the the cockpit wall! Longer would give you more mounting options later!

Yes, the water inlet is the seacock. If you have a raw water strainer, take the top off (where you check for seaweed, etc) and then open the handle of the seacock - see how much water comes out. If lots comes out, then you do not have a problem with an obstruction in the intake opening / thru-hull (or at least it's not totally bocked) *** Mkae sure you close the seacock, so the boat doesn't sink after!! Seacocks are open when the handle is parallel with the flow of water, and closed when the handle is perpendicular, to the flow of water!!***

[Jack Long]

I went back to the boat armed with a water temp gauge, an exhaust flapper, a waterpump rebuild kit, and sundry other items to address unrelated issues. I already had oil and a filter on board.

The anchorage was a nightmare. High frequency chop of 2-3 feet or so had the boat rocking from 25' to 25'. It was foggy so everything was wet wet wet. I would describe the conditions as generally miserable.

It turns out the exhaust doesn't even exit the boat on the transom but under the hull. Furthermore, it is not the sort of fixture that the flapper would fit on. So that job was put aside.

I opened up the motor cover and tried to track down the water temperature sensor and was unsuccessful. Everything from the gauge cluster goes into a tube of electrical tape and then is set free directly under the bulkhead from the lazerette to the engine compartment. I was not quite motivated to strip off the whole electrical tape mummification job the previous owner did. I am not sure how much of my problem was the conditions vs. my experience. I am sure I can find the sensor here at port. I rationalized that while knowing the water temperature would be cool- that it wouldn't really make a difference in the temp. So I put that job aside.

I removed and disassembled the water pump. The impeller looked great and I could control the flow of water out of the removed pump by opening and closing the thru-hull valve. So I knew I had water and it looked like my pumping mechanism was in good shape. It was missing a gasket and all the screws were fairly stripped. I tightened them as best I could with some pliers. After it was reassembled I had a bit of leakage and I wasn't sure if this was the plier tightening, the lack of a gasket, or if I cracked one of the hoses. It was just a drop and I figured it would be fine since there is an unlimited supply of water.

As I mentioned before the heat exchanger was off my radar at this time and so I was about out of tricks in my bag. I figured I would run the motor a bit and see if I was struck my inspiration. I turned the key, the right lights come on, I press the start button, and... nothing.

The batteries looked charged but the volt meter wired to them has fooled me before and I had a brand new battery just sitting on the floor and some new 20' jumper cables from West Marine (on sale for 14 bucks! The computer tried to charge me 39 or something but I made the clerk look at the sign and got the sale price) so I jumped in a third battery. Still NOTHING from the starter button.

To avoid draining the new battery into some possibly fouled system I quickly unjumped it. Then I turned to Nigel Calder for help as I had found his marine diesel book. The first thing I see when I open to the "not starting" section is something about how if there is plenty of power and the motor won't turn that there could be salt water in the cylinders from back siphoning. If you recall my original post this was my number 1 suspect on the overheating mystery. The directions indicated turning the motor by hand with the decompression lever pressed to pump out the water- then trying to start the motor. I did this and it fired right up.

I quickly shut it down though so I can make sure I don't have other things to do to prevent a repeat or something. The book indicated that I needed to check for water in the oil. I could not find the dipstick. Seriously, I will post pictures later- I cannot find the dipstick. Nor could I find the drain plug. The book said they are often hard to find- I have no idea where the damn thing is. So I removed the oil filter. The oil looked pretty good. I put a new filter on. Then I moved on to other projects.

Later in the afternoon I decided to run the motor a bit so I could charge some things. I go to start it and... nothing. Just like before. No way! But, feeling confident I run through my hand cranking procedure. Nothing. I return to Nigel for guidence. Now I am looking at a little choose-your-own adventure thing and I start working through. One of the steps involves jumping the battery terminal to the start switch terminal on the soleinoid. If this works, indicates Nigel, there is a problem in the starter switch system. Well damn! Maybe the button is just intermittent and my hand cranking was just an excercise?

Anyway, I disassembled the gauge cluster panel so I could access the back of the switch. I was hoping I would find something obviously loose but no such luck. Feeling a little defeated I called to see if I could get a water taxi back off the boat. I figured I would go spend more money on stuff and come back the next day. The taxi was already shut down. I was stuck. Well, to hell with it then, I cleaned up my mess, dropped the mooring rope, and sailed for home.

I had much better wind than the trip down but still some longish periods of nothing. I fiddled with the start button so I could feel like I wasn't powerless until it happened to catch. Then I left the motor running most of the way home without any alarms. I am more convinced than ever that the overheating was from the following sea clogging the exhaust.

Anyway, it took me 23 hours to get back to Redwood City from Capitola. I saw three whales in Half Moon Bay too!

I have plenty of jobs lined up for myself for the next few days but will probably start a new thread on the anti-siphon stuff in a week or so.

[Ex-Calif]

Jack - You might want to start separate threads for each item or this could get confusing quick.

In regards to the start problem. When you say "nothing" what does that mean? You have lights on the guage panel so you have power. Do you get a click? Do the lights dim? With no lights diming and no click of the engine solenoid it could be the start switch, start relay or the engine solenoid.

In regards to the water leak from the pump, that doesn't sound good. No gasket and stripped threads doesn't sound good either. You might want to think about this. A replacement pump is good insurance for as far as you want to travel.

BTW - Regarding the wet conditions and 25 degree side to side heel - Welcome to cruising = Fixing boats in exotic locations...

[Northeaster]

re: finding the temp sensor - you don't need to start tracing from the buzzer / alarm panel. Just start tracing out your water system, and look for a small fitting with a wire attached to it. They would often be located near where the thermostat is / where the water exits the engine heading for the ehat exchanger (or exhaust elbow, if it were raw water cooled only, with no heat exchanger)

Don't be discouraged, doing it yourself is the best way to learn. However if you can invite someone onboard, who has experience with sailbaot engine / systems, to show you through the systems, it would be worth a case of beer - and cust down on your learning time!!

I would definitely look for replacement screws for the pump housing, and a new gasket - if it is leaking,m it could suck air in., and reduce the engine's abililty to cool itself as well.

[TabbyCat]

Jack,
Two suggestions:
1. Are you running the blower when you operate your engine? The blower recirculates cooler air from outside in to your hot engine compartment. We found on our previous boat that the engine would overheat and alarm if we didn't run the blower on long trips. We diagnosed this by opening the hatch over the engine when it was alarming - the alarm went off after a minute or two, so we knew it was a temperature problem.
2. Get a Speedseal to cover the water pump impeller. It is a plate with thumbscrew that replaces the existing cover for the water pump. It's easy to take off, and you won't strip the screws anymore. If you have any air getting into the water pump through the current gasket /cover, you can burn up impellers and potentially damage your engine if you continue to run it. You can find Speedseal on the internet.

[Jack Long]

I am running the blower although I suppose it could be providing inadequate circulation. The impeller looked good and I bought 6 new screws (bolts?) with tiny hex heads to avoid stripping them. The ambient temperature when all this occured was pretty low- 50s/60s so I would hate to think it was the external air temp since I am headed south!

Maybe if I ignore it it will go away? (kidding)

I've heard people talk about the exhaust being too hot as an indicator. Is there a good way to quantify this? My exhaust is really long and a little more than halfway through the big anti-siphon bend is a small hole that spits out soot and heat. I bought stuff to fix this up but am a little worried about what the root cause might be. I seem to get a lot of throughput out the back of the system- lots of bubbles and splashing...

[Chief Engineer]

Past the cooling inlet for the exhaust, you should be able to keep your hand on the hose. If you have a leak in the hose....don't try to repair it...replace it.

[Alan Wheeler]

My exhaust is really long and a little more than halfway through the big anti-siphon bend is a small hole that spits out soot and heat.

I assume this is the exhaust riser you are describing. This is not an anti-siphon loop, but better described as a damn to stop water running back down the exhaust from the cooling water entry and seawater from running back down the exhaust. The exhaust in that loop is dry and thus very hot. The risers can be cast iron or sometime SST. The SST is lighter and looks nice, but is subject to cracking. The cast iron is very heavy and can also crack and corrode away, but tends to last longer. Patching the riser will not last. You need to remove it and see what is actually wrong and get it replaced or welded if it can be. While this is removed, check the area the cold salt water is introduced. This can be a point where blockages can occur. Blockages can casue overheating and loss of power. If you have a very long exhaust, this can also cause over heating and loss of power. You need to ensure the exhaust is spec'd the correct diameter to length.

[Jack Long]

Alan,

I took some pictures the other day (before you posted this) but now I see that the perspective is terrible and you can't really see what is going on. I will need to take some new ones...

Let me see if I am understanding you. The exhaust leaves the motor dry so the hot water must leave the motor separately? Then it re-enters the exhaust before the damn?

The hole I am describing is on the far end of the damn but before the water is re-introduced. It is VERY far from the motor. I would say the exhaust needs to travel 7 or 8 feet to even reach the damn then the damn adds 4 feet or so of travel.

I looked into the paperwork that came with the boat and the motor was installed in 1981 and the work was done professionally. I think modifying the setup would be a substantial amount of work (and I leave for Mexico in less than a month) and with the sort of circumstantial evidence I just listed I am prone to think the setup isn't completely crazy...

So other than trying to track down what spec was for the 1981 motor- any suggestions on tracking down the root cause?

[HorizonMarine]

A couple of comments..

About cross threading the npt. We (i have a yacht service company) regularly add temp gauges to the Yanmars which requires using a new sender in the yanmar plugged hole. You can buy a Yanmar sender for big bucks or the normal USA version for 20 bucks. But,,, run a tap through the hole first. It will then screw in and out easily, with no leaks.

When your boat does not start, it is the easiest engine there is to hotwire. easiest way is to use a remote starter switch (Harbor Freight Tools for less than $10). next easiest is to get a jumper wire with an alligator clip at the end. Clip this on the large wire that goes to starter. Then touch the other end to the spot where the small wire goes to the starter. (Both these wires are technically on the selenoid which is the smaller cylinder that rides on the starter.) On a Yanmar, the key does not even have to be on, but it should so the alarms are available.

Overheating... On the saltwater side. pull the hose going to the pump. Is tehre a free flow of water?? Will it fill a soda can in about ten seconds?? good

next, pull the hose that comes out from the pump. Pretty powerful flow?? good.

next.. Pul the hose where it injects into the exhaust pipe behind the engine. Almost as strong as the previous?? good.

next .. is the inlet (metal part) where the water goes into the exhaust clear?/ They like to carbon up and clog the pipe. Stick something in it. On most of the yanmars, they recommend changing these entire fittings every 1000 hours.

FRESh water side. If you think it may be the thermostat, you can pull that out and run engine w/o it. If it fixes the problem, replace it. Comes out with two bolts. FYI.. Boil water in a cup and drop the thermostat in it and you can watch it open. Pull it out and see it close.

One other thought. About 6 times a year we see "spun" impellers. These impellers look fine. May even work well at slower speeds. But when the engine revs up, the rubber parts spins free of the metal part, so the metal spins, the impeller stops. Tough to diagnose. change your impeller on a regular basis..

Good luck!

[Alan Wheeler]

Sorry I came into this discussion half way through. I tried scooting back through your posts and could not see if you mentioned the engine. Sorry if you did, but can I ask again what it is? Plus do you have an actual temperature it is reaching? It is possible the alarm is simply going off for no real reason other than the sensor is a low rating.
It doesn't sound like a Yanmar with an exhaust set up like that. A long dry section of exhaust will be creating a huge amount of heat in the engine compartment. I would be looking at getting the water introduced earlier if you can. But that means the riser/mixer needs to be closer to the engine exhaust outlet. Is the hot exhaust section SST? This material is natorious for cracking. But there is no real better substitute. You need to get that hole repaired, but it won't cause heating problems. It will cause Co fumes in the boat though, so get it fixed.
By any chance have you a Perkins engine? Some of the Perkins will set of

[Jack Long]

Horizon, I might need to ask for a bit more data on some of those points but I love the practical exercise thing. I will try some of those metrics.

Alan, no worries! It is *absolutely* a Yanmar. Yanmar plate on the engine, Yanmar manual in the boat, motor and gauge cluster matches that from the Yanmar manual I was linked to online (the manual in the boat is crap- I think it was the thing that came with the motor), and lastly, a reciept from a shop for the installation of said Yanmar.

It is possible that the long section is wet. There is a rubb-

Hhhmm....

My last couple posts are "blind" as I am not at the boat. There is a hose being introduced to the exhaust after the "damn" which is where somebody said the water should come in and I think I assumed it was the hot water from the engine. On second thought- I think the bilge actually gets dumped into the exhaust right before it leaves the boat. I think they share a thru-hull. If that is true the hot water could enter the system just about anywhere.

I will look tomorrow and then we can know for sure.

A lot of this can be potentially really hard to track down though because it is not overheating regularly.

On the trip down to Capitola it overheated several times in a short period (probably wasn't getting much cooler than just below the alarm's threshold) with very low ambient temperatures (55 or so). Then it ran fine for several more hours. Shortly after dawn it overheated twice more- roughly an hour of run time apart.

On the trip back I ran the motor for 23 hours and it overheated only once about halfway through the trip. I started the trip at 7PM and it ran fine through the cold night- overheated at about dawn- then ran fine through the normal temps of the day.

[Alan Wheeler]

OK once you take a look, it could help shed more accurate info. It is highly possible it is not overheating but simply needs a hotter rated temp switch.
I don't like the idea of bilge pumping into exhaust. That is asking for trouble in several ways. If it is a true yanmar setup, the cooling water, which will be quite warm water will be introduced very soon after the exhaust section. If this is a proper yanmar mixer, they are prone to blocking up and well worth a check of that area. I would expect a rubber hose from that point. The riser further down must be to stop the bilge from flowing back up the exhaust. But if your bilge has to pump while the engine is running, either/either is going to be restricted. Plus the exhaust exiting well below the waterline under the hull is also placing a large restriction to the exhaust and that creates backpressure and also causes heat build up in the engine.

[Jack Long]

Okay, at the boat now!

The water enters the exhaust right after the motor- 10 inches or so. Then a long pipe what tilts slightly down for 6 feet, the a slight up tilt for another foot and a half or so- then the riser. Bilge enters the system right before it exits the boat- maybe 4 inches. I would guess that in still water the thru-hull is 4-6 inches under water. Hard for me to tell with the various curved surfaces.

I was reading in Nigel Calder's Marine Diesel Engines book this morning that a weakness in the fresh water cooled system is the build up of silt and scaling. This is what I was thinking about when I asked about pickling. His book doesn't give any suggestions on how to fight this. Would running the engine for some number of hours on clean fresh water help rinse that stuff out or something? The section basically read like boats with fresh water cooling have a half-life and then die... Makes me a bit nervous.

[Alan Wheeler]

Sorry, do you mean fresh water cooling or salt/raw water cooling. Salt or raw water cooling is the one that can cause scale and salt build up inside the engine along with corrosion. Fresh water cooling means you have a captive circulating system that is being cooled via a heat exchanger that is cooled by the Salt water. Fresh water cooling means you can and should have anti-corrosion inhibitor added. One thing that can take place inside the internal water jackets is cavitation corrosion and anti-corrosion inhibitors stop that from happening. They also ensure more efficient heat transfer through the cooling system.
As I said earlier, you need to fix the exhaust and you need to test the actual operating temp. It could be the temp is OK. It has happened before.