Yanmar 2gm engine died

[Davidasailor26]

throt·tle (thrŏtl)

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n.
1. A valve that regulates the flow of a fluid, such as the valve in an internal-combustion engine that controls the amount of air-fuel mixture entering the cylinders.
2. A lever or pedal controlling such a valve.
tr.v. throt·tled, throt·tling, throt·tles
1.
a. To regulate the flow of (fuel) in an engine.
b. To regulate the speed of (an engine) with a throttle.
2. To suppress: tried to throttle the press.
3. To strangle (a person); choke.

Interesting discrepancy in that set of definitions. As a noun the throttle is limited to being a valve or the lever controlling a valve, but as a verb it means to regulate the flow of fuel, regardless of whether you’re regulating it with a valve or by changing the output of a pump. So you could throttle an engine without using a throttle!?

 

[3GGG]

Your engine shows an RPM on your Tach.
The spec for the Yanmar 2GM is
The continuous rating output at the crankshaft is 11.8 kW, at 3400 revolutions per minute (rpm). The maximum output at the crankshaft is 13.4 kW, at 3600 rpm.
80%is 2880 RPM. The Spec says you can run the engine at 3400. On your boat you need to identify what RPM gets you to your hull speed. If it is below 3400 that would be golden. If it is at 2880 that would mean you could run the engine at that RPM all day and go as fast as your boat hull permits. You would have reserve power to deal with foul weather conditions.

For this exercise to resolve the oil issue, I would run the engine spinning the prop at the dock fast enough for the engine temp to get up to 125ºF. I would record the RPM needed to reach this temp range. Once the engine temp hits that range I would shut down and change the oil. Note the oil will be hot take precaution not to get burnt. Pumping out the oil should be easy. Change the filter and then pour in new oil. Repeat the process.

The throttle drift is a separate issue. More info is needed. I would look at the linkage. You may have something loose in the linkage. Throttles are designed to be set and stay at that position. Not sure what type of throttle linkage you have.

I dont have a working tach or an oil temp gauge. Tach is on the list to fix

 

[smokey73]

While not convenient for normal underway operations, you can purchase a digital tach fairly cheaply on Amazon or at your local auto parts store. You attach reflective strip to the engine drive pully. The "gun" is pointed at the spinning pully and reads the rpm. It is a useful tool to check the set and check the accuracy of your tach (when you get around to installing one.) It is also useful when trouble shooting engine performance issues, especially if you don't trust or believe you tach. Not expensive and a very useful tool for the situation you are in

 

[smokey73]

You don't really mean an Oil Temp gauge. I think you mean an Oil Pressure Gauge. If you know the threaded fitting size where the oil pressure sender should fit (either National Pipe Thread (NPT) or British Standard Pipe Thread (BPST)) you can purchase a mechanical gauge for about $35 and at least temporarily get a reading on your actual oil pressure. MAKE SURE you use the correct pipe thread for your engine. I am sure someone on here can tell you the correct thread you will need.

If it is temperature you are interested in you need a Engine Temperature gauge or as a temporary alternative you can buy a IR temp gun (fairly inexpensive for "non- precision gauges) and take a reading on the output side of the engine thermostat. Again, not convenient nor advised for normal underway operation but you can use it for troubleshooting.

 

[smokey73]

If it is a Yanmar, then it is probably a BSPT (which I believe is the same as Japanese Standard Pipe Thread) unless the PO messed around with the fitting at some time in the past. If it is, you can buy a fitting with a male BSPT and a NPT female so you can use a guage from any auto parts store.

 

[jssailem]

@3GGG For your purpose, what @smokey73 describes would be reasonably cost-effective temporary solutions and yield important data for your boat ownership. The temperature I spoke of was engine temperature, but it could also be oil temperature. The IR gauges would give you the answer you seek.

 

[Dalliance]

While not convenient for normal underway operations, you can purchase a digital tach fairly cheaply on Amazon or at your local auto parts store. You attach reflective strip to the engine drive pully. The "gun" is pointed at the spinning pully and reads the rpm. It is a useful tool to check the set and check the accuracy of your tach (when you get around to installing one.) It is also useful when trouble shooting engine performance issues, especially if you don't trust or believe you tach. Not expensive and a very useful tool for the situation you are in

I bought one recently, about $16 from Amazon, because I suspected my Yanmar tachometer was inaccurate. This tool confirmed my suspicions. My Yanmar tachometer consistently reads about 25% low. I don’t know if there’s a way to recalibrate it, but it’s not critical. Now that I know, I can do that math.

 

[smokey73]

A replacement tach (not from Yanmar) is not to terribly expensive and depending on the brand, you can "calibrate it" when you set it up. I'll try to dig up a link to the one I bought. It fit the stock hole (with a little tweaking) in the instrument panel and used the flywheel pickup as the original did. With the digital tach you can calibrate it down to about +- 25 rpm or so. I am very happy with mine.

 

[Hayden Watson]

Dave, I do not believe that is correct. Marine diesels, as with most/all diesels, have speed controls: a governor connected to the high pressure injector pump. When we advance the so-called throttle [1] it adjusts the governor for a higher target RPM, and the governor controls the injector pump to supply the correct amount of fuel to maintain that RPM, over varying loads.

[1] there is no throttle on a diesel engine. There's a speed control, and is connected to the governor, and controls the engine RPM. It works in concert with the injector pump to supply the right amount of fuel to maintain the RPM over varying loads. It's weird, as even diesel vendors/manufacturers will use the term throttle and "WOT" (wide open throttle) in their literature, even though there's no throttle.

This is correct for the Universal (Kubota) engines and many diesels but not all. The Cummins engine does not have the governor directly connected to the throttle pedal. They behave more like a gas engine in that if you give it a little bit of peddle in neutral, the engine speed will go up to the maximum speed allowed by the governor. I have never driven a boat with a Yanmar so do not know if their throttle is connected to the governor or not.

 

[Ralph Johnstone]

During the runs after the oil changes, i need to run 80% of WOT?

Run at 80% as a rule, not always but out in the open 80%. If sitting at the dock idling in neutral after the first oil change, the engine is set at 800 RPM. If out by a mile, set the low speed. Which reminds me, look in the download section on this site to find the service manual for your engine. No guarantees but it SHOULD be there.

I will do this. My first diesel so I don't know what clean diesel oil looks like. Should I assume after 3rd full oil change it would be reasonably clean?

Not necessarily. Just depends on how the used oil looks as you change the oil. If you can run it around 3K and the oil is reasonably clean, you've eliminated all crap.

REMEMBER : after about 10 hours of running time, you will see the oil is black and opaque. An exact match for road tar in colour. No need for a heart attack. This is NORMAL and will stay like that until you reach 100 hrs. and ready for another oil change. Same for me when I had "0" hours on my engine.

I can think of nothing worse for a diesel engine.
Why is this?

For excessive hours of idling or running a diesel far below 80%, this is a recipe for trouble over the long haul. The general thought from the course I took and books I've read, the prevailing idea is that, as mentioned here, the engine is designed to run at a given RPM for several benefits.

When the engine runs below that speed, after many hours, the exhaust valve is not seeing the desired HP scouring gasses when it opens and the valve and its seat become coated with carbon. This carbon acts as an insulator and the valve is not cooled properly by thermal conduction into the block. This causes the hot valve to become cut by high pressure gasses and leaks around the seat during the power stroke. This further cuts the valve. The cylinder then sees lower pressure and lower temp. air on the compression stroke so poorer combustion results during the power stroke.

A vicious circle at its finest.


One of the worst things you will see is the idiots who come down to run their engines at idle during the winter. What they are actually doing is creating water vapour which condenses in the oil to produce sulphuric acid which works its magic on all the metal parts in the engine. The engine expects to be run until it is hot so the water is driven off. All by design.

 

[smokey73]

I believe my replacement tach was a Viewline 85MM tach that is available on Amazon and other sites. I am not sure it is made by VDO anymore and it may be Veratron. You'll need to check the spec like size, and tach range. My max rated RPM is 3600 so I bought one that went to 4000 rpm. It can take different triggering sensors like from the Alternator OR from the flywheel (which is what my original tach used). You'll need to know the number of teeth on your flywheel if that is the input sensor but that info is available with some research.