shaky Yanmar 1gm10

[solent clown]

With dropping in the water approaching, I managed to give the engine a proper run today to test the cooling system.
It has brand new engine mounts. It runs smoothly and seems well balanced for a single cylinder at half revs, and well, everywhere else but idle, where is it thumping and jumping a bit more than I am comfortable with. Obviously I am not planning to leave it ticking over in neutral for prolonged periods, especially as we have another charging set for batteries.
I can see that the mounts are very soft compared to the automotive style I am used to, and understand this is to negate noise and vibration.
What I do not like is I can see the vibration going down the stern tube and a slight wobble. Yes it does go away when it is revved up.
I did grease the cutlass bearing and knock it into gear a couple of times for a second or two, and it smoothed out again instantly with a touch of throttle.
I am assuming (hoping) this is fairly normal

 

[pvb]

Maybe raise the idle speed a bit?

 

[solent clown]

Maybe raise the idle speed a bit?

yes, I will try to tune it out, I just dont want to be smashing it into gear at high revs. I can live with a bit of shaking if it's normal.

 

[pvb]

yes, I will try to tune it out, I just dont want to be smashing it into gear at high revs. I can live with a bit of shaking if it's normal.

Were the new mounts the recommended type?

 

[solent clown]

Were the new mounts the recommended type?

yes mate

 

[pvb]

A single-cylinder diesel will vibrate a bit more than multi-cylinder engines, but if you can vary the idle speed until you find a sweet spot it should be OK.

 

[JVL]

With dropping in the water approaching, I managed to give the engine a proper run today to test the cooling system.
It has brand new engine mounts. It runs smoothly and seems well balanced for a single cylinder at half revs, and well, everywhere else but idle, where is it thumping and jumping a bit more than I am comfortable with. Obviously I am not planning to leave it ticking over in neutral for prolonged periods, especially as we have another charging set for batteries.
I can see that the mounts are very soft compared to the automotive style I am used to, and understand this is to negate noise and vibration.
What I do not like is I can see the vibration going down the stern tube and a slight wobble. Yes it does go away when it is revved up.
I did grease the cutlass bearing and knock it into gear a couple of times for a second or two, and it smoothed out again instantly with a touch of throttle.
I am assuming (hoping) this is fairly normal

1gm 10 idle speed is 850 -900 its best set once the engine is at running temp!
All the gm series think they are kangaroos at low revs.

John

 

[solent clown]

1gm 10 idle speed is 850 -900 its best set once the engine is at running temp!
All the gm series think they are kangaroos at low revs.

John

that's what I needed to hear. Our donkey/genny engine is a 4hp Hatz single cylinder, that is not as jumpy, but then again it does not have a gearbox hanging off it.

 

[solent clown]

A single-cylinder diesel will vibrate a bit more than multi-cylinder engines, but if you can vary the idle speed until you find a sweet spot it should be OK.

Yes, we will try to compromise idle speed to vibration when we get it in the water. It was reassuring to see it settled right down at revs. Some engine are just not well balanced at idle, even some of the v8s we work with in the day job, but is part of their charm. Cars however do not sink...

 

[Appledore]

1gm 10 idle speed is 850 -900 its best set once the engine is at running temp!
All the gm series think they are kangaroos at low revs.

John

My 1GM10 ticks over quite smoothly at low revs, and I guess it's a matter of balance. Perhaps the engine mounts are just too soft?

 

[solent clown]

My 1GM10 ticks over quite smoothly at low revs, and I guess it's a matter of balance. Perhaps the engine mounts are just too soft?

I will post a vid tomorrow, my idea of smooth, and a yachtsman's may well be very different things. I suppose in reality it is rarely if ever going to be at idle, and if we maintain our discipline about not using an engine it will be less of an issue - however I know we will end up using it just to get into the solent proper quicker, and to do so many other things rather than stare up at a slack sail praying for wind.

 

[Pords]

Sounds normal to me. Had a 1gm10, completely rebuilt it when the head failed and it did exactly the same. If you go on youtube you will see plenty of the Yanmars bouncey around at idle. Some more than others i might add. But this will be down to engine mounts used.

 

[JumbleDuck]

My 1GM10 ticks over quite smoothly at low revs, and I guess it's a matter of balance. Perhaps the engine mounts are just too soft?

In general, stiffening up mounts only makes things worse. You hit resonance at a higher frequency, but since the forces are proportional to the frequency squared the amplitude of vibration when you do hit resonance is far worse. This is why washing machines go wild at very low speeds - their drums have very soft suspension - and then spin smoothly.

Sounds to me as if the OP's engine is ticking over at resonance, and that just a small tweak, ideally up, in idle speed could sort things.

 

[JumbleDuck]

A single-cylinder diesel will vibrate a bit more than multi-cylinder engines, but if you can vary the idle speed until you find a sweet spot it should be OK.

From bitter experience, a two is just as bad as a single, since both pistons move up and down together. You gain a very little from having one bang per revolution instead of every two, but it's not a huge effect. My Nanni N2.14 is every bit as vibration-y as its predecessor 1GM10 was. Also more complicated, tighter fit and less reliable. What a waste of money that was.

 

[KenMcCulloch]

When I had a boat with one of these engines, my biggest worry was the 12v battery cables chafing where they passed through a bulkhead, when the engine was doing its little dance. They nearly all do that, apparently.

 

[solent clown]

turned the revs up a tad, less jumpy, and less noisy.
As an aside, what a pig of an engine to bleed. I have vast experience of diesel engines of many vintages, sizes and levels of sophistication, but this little buggar really gave me some trouble for half an hour.

 

[mickywillis]

When I had Zara with a 1GM10 in, I used a Pela vacuum extractor pump to bleed through when changing filters. Dead easy and it took about 5 mins to bleed everything and get her running OK.

 

[Cuan]

Thats interesting, how did you do that?

When I had Zara with a 1GM10 in, I used a Pela vacuum extractor pump to bleed through when changing filters. Dead easy and it took about 5 mins to bleed everything and get her running OK.

 

[DownWest]

On the same engine, I put an outboard type squeezy pump in the line. Bleeding was a doddle, much faster than the lift pump.

 

[solent clown]

I just had an airlock in the secondary filter, and instead of doing the obvious and opening the bleed I pissed about for ages. I only fired it up a couple of weeks back, jury rigged fuel system and it fired straight up. I must have used the last of the fuel in the filter as I switched it up.
As soon as I cracked the bleed the fuel flowed straight in without any pumping.
The fringe benefit was my son learned the proper bleed procedure for an old diesel as I took him though it after.
I think the main problem was we forgot the workshop tradition of praying to the Gods of Steel and Thunder before starting an engine.
Battery was flat, so we cranked it on decompress to get it spinning then fired it up.