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Old 19-04-2021, 19:02   #1
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Question 2QM15 shut down by throttling back?

We started and ran our new-to-us 2QM15 yesterday. She seems to start and run nicely. We are still on the hard & only had a 5 gallon bucket of water for cooling, so we really probably ran her for about 5 minutes.

I've never had a motor that was shut down simply by bringing the throttle back, so this is new for me. We seem to idle nicely with the throttle lever maybe 30% forward of the full back position. Any less throttle and the motor will die, which seems to make it WAY to easy to shut off the motor. The previous owner had some docking fun due to this.

I'm hampered by my ignorance of how this is supposed to work. I'd expect the "off" position to be at the extreme end of the throttle travel, maybe with a detent or something to require a deliberate motion for shut down. Are we in need so some cable adjusting? Or- is this just an indication that the motor is cold?

I didn't find any wisdom in the Yanmar manual. I'm sure this has been asked here before, but I can't find any previous threads.

Thanks!
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Old 19-04-2021, 20:23   #2
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Re: 2QM15 shut down by throttling back?

Our good old boat, which we acquired last year, has a 2QM20, which also shuts down by throttling back and that seems to be a nice way of doing it. However, the shut-down position on our throttle is the last 1/4-inch of possible travel, so it may be that your cable does need adjusting. We also have an emergency decompression pull that is linked by a cable to the cylinder head, but Yanmar does not recommend that for a regular shut-down, only for emergency use.


This is my first diesel engine, all of my previous ones have been gas-powered, including a good old Atomic IV. So I have no preconceptions about how things should work. I must say that the function of my engine and controls have been impressively smooth so far. If I do inadvertently go past the shut-down point on the throttle lever, I still have a second or so to recover before the engine actually dies.
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Old 19-04-2021, 21:24   #3
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by kayakerChuck View Post
We started and ran our new-to-us 2QM15 yesterday. She seems to start and run nicely. We are still on the hard & only had a 5 gallon bucket of water for cooling, so we really probably ran her for about 5 minutes.

I've never had a motor that was shut down simply by bringing the throttle back, so this is new for me. We seem to idle nicely with the throttle lever maybe 30% forward of the full back position. Any less throttle and the motor will die, which seems to make it WAY to easy to shut off the motor. The previous owner had some docking fun due to this.

I'm hampered by my ignorance of how this is supposed to work. I'd expect the "off" position to be at the extreme end of the throttle travel, maybe with a detent or something to require a deliberate motion for shut down. Are we in need so some cable adjusting? Or- is this just an indication that the motor is cold?

I didn't find any wisdom in the Yanmar manual. I'm sure this has been asked here before, but I can't find any previous threads.

Thanks!

You have a problem Chuck.
There should be an engine stop knob on your instrument panel & that should be the only way to stop the engine.
The cockpit remote control is only there to select neutral, fwd or reverse & how much throttle in either mode. It should idle at a minimum of 650rpm in neutral.

There could be multiple reasons why it wont idle. I'd suspect an air leak or fuel or air restriction first off.

However check the throttle linkages to the governor first.
Check fuel & air filters & make sure fuel is flowing from the tank easily & that vent is ok.
You will inherit the docking dramas unless you deal with it.
Do you have the workshop manual or only the operating manual?
I can send you a free 2QM15 PDF if its not in the CF library
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Old 20-04-2021, 05:32   #4
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Re: 2QM15 shut down by throttling back?

Suggestion: Loosen the throttle at the engine, and pull the throttle all the way back at the helm. Start the engine, and adjust the linkage at the engine until you get a good 650 or so RPM. Tighten. Then, start the engine and demonstrate that if you slam the throttle back at the helm the engine does not shut off, but does go to that low idle.

When you are maneuvering at the marina, and about to spear a megayacht with your bowsprit, you are going to slam back the throttle. That's not when you want the engine to stall.
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Old 20-04-2021, 06:15   #5
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by Compass790 View Post
There should be an engine stop knob on your instrument panel & that should be the only way to stop the engine.
FWIW, the only way to stop my 2QM15 is to also throttle all the way down. I have the original instrument panel and there is no stop knob or a hole missing for one.

That being said, mine dies at the last 5%-10% of the arc of turn
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Old 20-04-2021, 06:34   #6
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by Compass790 View Post
You have a problem Chuck.
There should be an engine stop knob on your instrument panel & that should be the only way to stop the engine.
The cockpit remote control is only there to select neutral, fwd or reverse & how much throttle in either mode. It should idle at a minimum of 650rpm in neutral.

There could be multiple reasons why it wont idle. I'd suspect an air leak or fuel or air restriction first off.

However check the throttle linkages to the governor first.
Check fuel & air filters & make sure fuel is flowing from the tank easily & that vent is ok.
You will inherit the docking dramas unless you deal with it.
Do you have the workshop manual or only the operating manual?
I can send you a free 2QM15 PDF if its not in the CF library


Most QM engines Iíve been around are shut down with the throttle. Normally there is a strong spring on the engine that must be overcome with pressure aft on the throttle to shut off the fuel. If the spring is weak or missing shut down may be too easy.
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Old 20-04-2021, 06:39   #7
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by Compass790 View Post
You have a problem Chuck.
There should be an engine stop knob on your instrument panel & that should be the only way to stop the engine.
The cockpit remote control is only there to select neutral, fwd or reverse & how much throttle in either mode. It should idle at a minimum of 650rpm in neutral.

There could be multiple reasons why it wont idle. I'd suspect an air leak or fuel or air restriction first off.

However check the throttle linkages to the governor first.
Check fuel & air filters & make sure fuel is flowing from the tank easily & that vent is ok.
You will inherit the docking dramas unless you deal with it.
Do you have the workshop manual or only the operating manual?
I can send you a free 2QM15 PDF if its not in the CF library
This is good advice ^^

And here is how the stop function works - the green line is the throttle cable and the red line is the stop cable. The throttle (regulator) and stop assembly is adjacent to the injector pump.

It is possible that a previous owner has removed the engine stop assembly in which case the throttle cable would move the regulator lever into the stop position.
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Old 20-04-2021, 06:43   #8
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by Sailmonkey View Post
Most QM engines Iíve been around are shut down with the throttle. Normally there is a strong spring on the engine that must be overcome with pressure aft on the throttle to shut off the fuel. If the spring is weak or missing shut down may be too easy.
The 2QM20 and 3QM30 comes in two variants - one as you have described and one as Compass790 has described.

AFAIK, the 2QM15 has only one arrangement which is how I have described it upthread.
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Old 20-04-2021, 07:14   #9
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Re: 2QM15 shut down by throttling back?

could the idle be set too low. Such that when you throttle back to idle instead of idling at 7-800 rpm its taking it much lower to the point of shutting the engine off. my perkins was doing this after I rebuilt the injection pump. and it took some tinkering with the idle adjustment screw to dial it back in. so when i went to idle it wouldn't shut off.



Another possibility. Mine is still a bit finicky when cold. but once warmed up, throttle back to idle is fine. Could be your yanmar is just cold natured and doesn't like idle when its cold.


https://www.cruisersforum.com/forums...eed-17687.html


not sure if you have it or not, but here is a link to the j30 website which has a bunch of useful info on the Yanmars. including parts and service manuals in PDF format.


http://j30.us/blog/?page_id=356
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Old 20-04-2021, 08:00   #10
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Re: 2QM15 shut down by throttling back?

I had the same problem with my 2QM15. It wouldn't idle and shut down, give it throttle and it was fine. My issue turned out to be the pull stop cable. I'd pull it out to stop the diesel and then push it in all the way. The stop cable would then creep back out by itself a small bit. Just enough that it wouldn't prevent it from starting (I set it to half throttle to start) but wouldn't allow it to idle. Guess you cant expect much from a 40 year old stiff and sticky cable. Replaced the stop cable, adjusted the stop screws at the lever and all is well.



You can try disconnect the stop cable at the lever on the top left of the Diesel, then see if it idles.
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Old 20-04-2021, 09:10   #11
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Re: 2QM15 shut down by throttling back?

When my too long remote cable to my engine stop lever began to jam up, I removed it and installed a 1/4” rope 3’ long that runs in a straight shot to the control panel. The rope is light enough and the spring back mechanism on the engine is strong enough to easily return to start position. I no longer use any of those sheathed remote cables for the gear box either which also failed. When rope fails, it’s an easy fix.
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Old 20-04-2021, 09:28   #12
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Re: 2QM15 shut down by throttling back?

Operation Manual:
https://sbo.sailboatowners.com/downl...n_55888915.pdf

Engine Service manual: https://sbo.sailboatowners.com/downl...n_34429454.pdf

Most (non-electronic) diesel engines use a "jerk pump" type injector pump which has two (three, if it has a "cold start" ) control inputs:

The "throttle" sets the engine speed which is then controlled by an internal governor which adds /subtracts the amount of diesel fuel being injected to maintain the selected ("set") speed.

The fuel cutoff input shifts the injector pump to the "zero fuel" mode where the internal injector pistons no longer provide any fuel to the injectors and the engine shuts down.

To have this in a single input to the injector pump would require combining both of these functions on the injector pump into one lever, (which I have not heard of), or possibly having an electrical SOLENOID which cuts off the fuel when the lever is pulled all the way back.

Another possibility is that when you pull the throttle all the way back, the engine "set" speed input is now so low that the engine can no longer idle and it just stumbles and "dies", (which IMHO is not a very good way to shut down an engine...)

cheers.
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Old 20-04-2021, 12:47   #13
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Re: 2QM15 shut down by throttling back?

Thanks all!

I have some homework to do. I'll report back what I find. Our boat is 3 hours away, so it's not easy to run over & check things :-)
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Old 20-04-2021, 14:24   #14
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Re: 2QM15 shut down by throttling back?

A lot of engines come that way, throttle all the way back to shut down. It's a bit cheaper with only one lever and cable and an easier install. Completely normal. But there should be a detent or higher resistance before you get to the stop position. Could be the control lever or cable needs adjustment, or a spring is weak or missing. Cable should be adjustable on the cockpit end and be adjusted so only the last little bit of travel kills the engine. Then examine the engine end to find a spring that increases the effort needed to move the lever. If there's not one there or one that is too compressed to work, most hardware stores have a good selection and should have one that works. It should take considerable pressure on the lever to get to the stop position.
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Old 20-04-2021, 14:48   #15
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Re: 2QM15 shut down by throttling back?

Quote:
Originally Posted by Compass790 View Post
You have a problem Chuck.
There should be an engine stop knob on your instrument panel & that should be the only way to stop the engine.
The cockpit remote control is only there to select neutral, fwd or reverse & how much throttle in either mode. It should idle at a minimum of 650rpm in neutral.

T
NOT SO! I had a 2QM15 from 1982 (with maybe ten hours on it) until 2004, and how shutting it down with the throttle is exactly how it works and how the manual said to run it. My panel had NO kill switch, although there may have been other panels available. I will say that I never shut down by accident...it was at the very lowest throttle setting, and while there was no detent, there was a very slight resistance. It was the model of reliability and consistency. Never did anything to it in all those years. My set-up had a separate gear shift and a separate throttle, as was common in those days, and the whole thing was explained and diagrammed in the manual. I would simply get that cable adjusted so that the "cut'off' is reached at the end of the travel.
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