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Old 07-02-2021, 14:51   #31
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Re: YANMAR RUNAWAY! Lessons Learned...

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Originally Posted by Compass790 View Post
Did you read to the btm of the page this time Wottie?
OOOHhh thats an underarm the engine rebuilding expertise crack.

........
I start at the btm of the page nowadays and yes, ya correct, it was underarm...

And regarding the ,
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Old 07-02-2021, 19:41   #32
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Re: YANMAR RUNAWAY! Lessons Learned...

SobeFlyer Thanks for the posting. I have the Yanmar 4JH - TE also.
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Old 07-02-2021, 20:41   #33
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Re: YANMAR RUNAWAY! Lessons Learned...

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Originally Posted by SobeFlyer View Post
For sake of discussion only, wouldn't my situation with a fuel rack stuck at WOT even if only feeding three cylinders meet your definition of "ungoverned source of fuel" ?



No, even if the governor guide is stuck on max , the governor wil still control the engine at its maximum rpm.


If the error is in the governor itself, worst case is still limited by the maximum stroke of the diesel pump. If unloaded offcourse, it can overrun quite badly.


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Old 11-02-2021, 18:55   #34
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Re: YANMAR RUNAWAY! Lessons Learned...

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Originally Posted by Bill Seal View Post
I'm sure the clattering you hear is just slop in the valve train because the decompression lever is holding the valve slightly off the seat. Sort of like a collapsed hydraulic lifter noise. If the piston would actually hit the valve, it would probably bend the pushrod even when hand cranking it.

Na, in my case, it is the piston hitting the exhaust v/v.
I proved it a few days ago by turning the engine by hand on the compression stroke up until it hits the exhaust valve whilst I'm holding the decompression lever open. I can feel it hit & I cant rotate the crankshaft any more until I back off on the decomp lever. The pushrod isnt in play on the compression stroke.

To be fair I have silicone as the rocker cover gasket which would affect the clearance & the rocker cover is off the earlier version motor ( ysb8) which I thought was identical but may not be.Both of those factors could well affect its throw causing the valve to contact the piston.
Not worried about it on our motor as its only knocking my hand back.

Wotname I was lucky the 3 knockdown rule wasnt in effect. I kept getting up & swinging but you have got the TKO anyway.


I wont post any more as its thread drift but just wanted to say the valve hitting the piston is probably peculiar to our engine so dont be frightened to use the decompression lever to stop a runaway diesel.
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Old 11-02-2021, 19:19   #35
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Re: YANMAR RUNAWAY! Lessons Learned...

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Originally Posted by bailsout View Post
What happens when you use the decompression levers? They would stop my Yanmar 2qm15, but not in a runaway situation that I have not yet faced.
Yeah that would work for stopping a runaway on your 2qm.

My 3qm has them. Very handy for many purposes.
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Old 12-02-2021, 07:44   #36
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Re: YANMAR RUNAWAY! Lessons Learned...

My dad witnessed this with a generator in the military. They tried blocking the intake and it wouldn't work. They ended up getting far away and just waited for the engine to blow. It sounds scary.
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Old 12-02-2021, 08:15   #37
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Re: YANMAR RUNAWAY! Lessons Learned...

All the poop about stopping the engine from a run-a-way sounds great but at some point (if not successful), it might be more prudent to get out of the area and let the engine go. You are basically sitting on a hand grenade while going through these exercises. The only difference is the rod parts and the block parts knocked out by the rods are somewhat larger than the fragments of the grenade.

It’s probably good to do what you can to a point but replacing a engine is cheaper than some of your body parts or worse.

Just sayin
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Old 12-02-2021, 08:29   #38
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Re: YANMAR RUNAWAY! Lessons Learned...

I once watched a locomotive engine run away and when it sucked up all the oil it seized up. Oil droplets were over everyones cars..
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Old 12-02-2021, 09:00   #39
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Re: YANMAR RUNAWAY! Lessons Learned...

I had a runaway once with my Yanmar YSM 12... the oil breather plate had somehow been installed upside down, by a friend mechanic who had repaired the engine for some other reason which escapes me now, but I took the boat out on a solo sail one Tuesday morning in the False Bay area off Simonstown in South Africa, and unbeknownst to me the SA Navy restricted this bay during naval operations every Tuesday!! and they were having missile training!

Well I was trying to get out of their way and was sailing hard pressed to windward, well heeled over and had the engine running for extra speed.... what happened next was an absolute nightmare for any sailor, solo or otherwise!

Suddenly my faithful, reliable engine shot up to maximum revs and I could NOT stop her, and at this stage I had left the helm, and was down below panicking and clawing and pulling cables to stop her and just did not know what to do..

The naval frigate I had been trying to avoid was a couple hundred yards off my starboard bow and I knew those had not been friendly waves the white clad officers were executing...! The engine continued to scream out of control and I suddenly recalled reading once about this ugly phenomena, and how to stop them from running away, which was to starve them of air. I was able to grab a settee cushion and stuffed it onto the air intake, slowly the revs came down and finally petered out.... I later found out that the engine had been feeding on her own sump oil!!! and this was how I figured out the oil screen plate had been put back upside down and had been triggered by my heeling over when beating upwind...and I was severely reprimanded by the yacht club Commodore for being out there in the first place!! More adventures were soon to follow, little did I know...
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Old 12-02-2021, 14:34   #40
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Re: YANMAR RUNAWAY! Lessons Learned...

1) POWER lever rather than speed (in your case, it did neither). I wonder why small diesel engines have governors rather than direct power control. Is it to prevent stalling when you engage drive ?
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Old 12-02-2021, 15:07   #41
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Re: YANMAR RUNAWAY! Lessons Learned...

As I understand it, the governor matches the fuel supplied to the speed selected according to the load the engine is under. Though I feel the qualifiers 'within reason' and 'theoretically' (used colloquially) should be added.

Think of it this way. You're tooling along on a level road at 3000 rpm. You start up a hill, increasing the load, causing the engine to slow. Since this also slows the governor, set at 'X', the governing mechanism increases the fuel supply to match the desired, set 'X' speed.

Conversely, when going down the other side of the hill, The engine overspeeds the 'X' setting, and the governor reduces the fuel supply until the desired RPM is reached.

So yes, the function of the governor is primarily associated with what in the automotive industry is called 'driveability'.

Again, that's at least the way I understand it...
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Old 12-02-2021, 15:35   #42
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Re: YANMAR RUNAWAY! Lessons Learned...

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Originally Posted by n5ama View Post
All the poop about stopping the engine from a run-a-way sounds great but at some point (if not successful), it might be more prudent to get out of the area and let the engine go. You are basically sitting on a hand grenade while going through these exercises. The only difference is the rod parts and the block parts knocked out by the rods are somewhat larger than the fragments of the grenade.

Itís probably good to do what you can to a point but replacing a engine is cheaper than some of your body parts or worse.

Just sayin
HUGE LOL!!!!
Love it!!
I would expound on the differences of a hand grenade and a 54 hp diesel engine....but why?
Seriously....just too funny.
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Old 12-02-2021, 16:09   #43
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Re: YANMAR RUNAWAY! Lessons Learned...

Like cruise control, but there aren't any hills to climb, and accurare speed control isn't really useful.
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Old 12-02-2021, 16:35   #44
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Re: YANMAR RUNAWAY! Lessons Learned...

If you think that's the case when running a boat, I suggest you try and operate a small boat diesel engine with control over only the injection pump fuel rack.

Seriously doubt you'd make it even a mile before screaming for the convenience of a governor.
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Old 12-02-2021, 16:58   #45
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Re: YANMAR RUNAWAY! Lessons Learned...

Quote:
Originally Posted by sailorladd View Post
I had a runaway once with my Yanmar YSM 12... the oil breather plate had somehow been installed upside down, by a friend mechanic who had repaired the engine for some other reason which escapes me now, but I took the boat out on a solo sail one Tuesday morning in the False Bay area off Simonstown in South Africa, and unbeknownst to me the SA Navy restricted this bay during naval operations every Tuesday!! and they were having missile training!

Well I was trying to get out of their way and was sailing hard pressed to windward, well heeled over and had the engine running for extra speed.... what happened next was an absolute nightmare for any sailor, solo or otherwise!

Suddenly my faithful, reliable engine shot up to maximum revs and I could NOT stop her, and at this stage I had left the helm, and was down below panicking and clawing and pulling cables to stop her and just did not know what to do..

The naval frigate I had been trying to avoid was a couple hundred yards off my starboard bow and I knew those had not been friendly waves the white clad officers were executing...! The engine continued to scream out of control and I suddenly recalled reading once about this ugly phenomena, and how to stop them from running away, which was to starve them of air. I was able to grab a settee cushion and stuffed it onto the air intake, slowly the revs came down and finally petered out.... I later found out that the engine had been feeding on her own sump oil!!! and this was how I figured out the oil screen plate had been put back upside down and had been triggered by my heeling over when beating upwind...and I was severely reprimanded by the yacht club Commodore for being out there in the first place!! More adventures were soon to follow, little did I know...

Good story!
You arent alone in that experience of the upside down big end access plate.
I sell rebuild parts for those old Yammers & just a couple of weeks ago a customer reported the same thing happened to him whilst motorsailing.
It was an engine re-conditioner who assembled his engine too.

It really needs a warning in the workshop manual about that.
Customer was after a new cover plate but I just told him to turn it the right way up with the vent pipes at the top.
You should have been able to stop it with the decompression lever but yea the fuel shutoff isn't going to do it.
I told the story in post 5 but its worth repeating

Did it suck up much oil?
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