Clifford_Pope
regular
Reged: 28/10/2005
Posts: 741
Loc: Pembrokeshire
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The yanmarhelp site is playing up again, so I'll try here:
My new engine has now clocked up 5 hours running time. It runs well, starts instantly, and is generally thoroughly satisfactory.
However, I worry a bit about the vibration/resonance. Occasionally, at no particular speed, it does a kind vibration which I can feel through the cockpit seat. It doesn't seem to actually move very much, but nonetheless the resonance can be felt.
Altering the throttle position makes no difference once it has started .
It is definitely in the engine (or gearbox) because it does it even in neutral with the prop shaft stationary.
I know the engine is not renowned for balance and smooth running, being a rather basic one-cylinder design, but how much vibration and resonance is normal?
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bendyone
regular
Reged: 19/01/2003
Posts: 1329
Loc: Calais
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I think this is normal, as you say it is a single cylinder engine. Mine used to do it at about 1800 revs on the seat. It just depends on the construction of the boat and which bits vibrate at what revs.
I have changed the engine to a 2 cylinder Nanni which is so much smoother.
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www.suzannah.eu
www.sailroom.co.uk
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KenMcCulloch
regular
Reged: 22/04/2007
Posts: 865
Loc: Edinburgh, Scotland
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Quote:
I know the engine is not renowned for balance and smooth running, being a rather basic one-cylinder design, but how much vibration and resonance is normal?
The short answer seems to be quite a lot. My personal theory is that it's the absence of a big heavy flywheel as found on some single cylinder marine diesels that makes the otherwise excellent wee Yanmar so bouncy and rattley. Mine vibrates quite a bit at tickover then smoothes out in the mid-range and becomes a bit rattley again at higher revs. As bendyone says it's probably a lot to do with the resonances of the hull and engine mounts as well.
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Ken McCulloch
Border Maid
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Robin2
regular
Reged: 20/12/2001
Posts: 639
Loc: Malahide, Ireland
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I found mine quietened down a lot when I installed aquadrive couplings between the engine and propeller shaft.
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Orange
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Severnman
regular
Reged: 03/07/2007
Posts: 51
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I echo KenMcCulloch's views. My IGM10 in a Foxhound 24, quite a lot of bounce at idle but diminishes with more throttle.
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loway
regular
Reged: 10/06/2006
Posts: 34
Loc: Thames Estuary
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For REAL vibration you need my Yanmar YSE8, a horizontal single cylinder. A 1GM10 is silky in comparison you lucky, lucky b**ger.
However, perhaps we need to hear from some Sabb owners on this topic.
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Clifford_Pope
regular
Reged: 28/10/2005
Posts: 741
Loc: Pembrokeshire
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I wondered whether there was a distiction between vibration - ie visible shaking from side to side on the flexible mounts, and a kind of drumming resonance that is half felt, half heard.
The feel is slightly reminiscent of that chattery way a supermarket trolley wheel can go on rough ground, or an old electric motor whose bearings need a drop of oil.
But it is a good point that it might be something in the construction of the boat resonating, rather than the engine itself. Perhaps it is to be expected that an old wooden boat has a lot of different resonance frequencies, rather than behaving as one rigid whole.
As I said, it does it irrespective of whether in gear or not, but perhaps the shaft can still transmit resonance even when not turning.
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Tranona
regular
Reged: 10/11/2007
Posts: 1361
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It could be many things. If you have a Vetus waterlock in the exhaust system this can set up a vibration if it touches any part of the boat structure. It could also be airborne resonance that might be reduced by extra sound proofing, but this is difficult to achieve in a traditional boat structure.
I remember sailing in a Sabre with a Brit 10 where you could tell cruising revs by the grid in the grill pan rattling!
I have had a 20 year affair with a 1GM with various different transmission arrangements. The smoothest was a rigid coupling and a floating shaft, but the banging of the shaft in the tube was worse than any resonance. Next iteration was a fixed shaft and coupling, which knackered the shaft bearings. Latest is a fixed shaft and a Bullflex, which overall is best, but resonance is back!
Every time I think it a problem, I remember its predecessor was a Stuart Turner!
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Clifford_Pope
regular
Reged: 28/10/2005
Posts: 741
Loc: Pembrokeshire
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Thanks everyone. So it's normal then.
And as Tranona says, better than a Stuart Turner.
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