1gm Yanmar lack of power Help

[spring]

I have an MG Spring fitted with a Yanmar 10gm. Flat out I only get 3.5 kt. Other owners get 6kt. The hull is clean - the gear box ratio and prop size has been checked and is correct. the stern bearing is not binding. When flat out I get some smoke and unburnt fuel in the exhaust. The engine has been serviced - injector and timing was checked as was the piston height (bent conrod) Also the exhaust manifold has been checked for blockage but no faults have been found. Otherwise the engine starts and runs very well.
But as I'm moored in Chichester could do with that extra 2 kts.

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[StugeronSteve]

Sorry if it's a silly answer but are you getting enough air to the engine under operational conditions? If the mechanical aspects have been checked it would seem to be a mixture problem.

Happy sailing and motoring. Steve.

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[Guest]

Particularly that you say you have unburnt fuel exhausting .....

Seems like an air starvation situation. How much ventilation do you have to the engine - is it nicely boxed in and insulated ? Maybe try it with the engine box lid off ????? to allow maximum air to get to the intake ?


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[pete]

Hi
A mate of mine has a spring and it had the same problem, as I have the same engine in my Hunter 27 we compared the props and there was a lot more blade area on my prop (a 2 blade prop) and from memory my prop was an inch larger diameter but the pitch appeared the same, we wondered if the prop had been altered to give less drag as it was used mainly for racing before he bought it, he has just replaced it and I think it has solved the problem

pete

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[jleaworthy]

This seems the most likely cause but check also your air filter. I know you only have one of those cone things made out of a sort of felt but they can get bunged up.

The other possibility is your exhaust. If you have a restriction it will reduce, by back pressure, the air getting into your engine. Flexible exhaust pipes can collapse internally if they have been overheated by cooling water failure. Unfortunately there is generally no external indication of this. If your exhaust is the original, presumably about fifteen years old, this is well worth investigating.
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[Birdseye]

check the simplest things first - we all tend to go for the most difficult if we're not careful.

1/ is the throttle mechanism operating properly ie does it fully turn the lever on the engine itself?
2/ are the diesel filters clean? no bug?
3/ is the air filter clean and properly assembled with the mesh on the inside?
4/ is the exhaust hose partially blocked / kinked?
5/ if no tacho fitted, beg borrow or steal a handheld one. check maxrevs under way. if max revs are as specified by yanmar (3800 on a 2gm) then think in terms of the prop. if way down, then lack of engine power.
6/ check tappet clearances
7/ the tap on the diesel tank fully open?

you're now in engineer territory if none of the above have worked.

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[dickh]

Check the obvious first.
Check the fuel filters - I had to change my primary mid season this year due to blockage - the first time ever.
Check the exhaust elbow is not blocked - this means REMOVING IT and checking on the bench!
I have had two instances of this being the problem, both on my boat and on a friends only this last week - fitted a new elbow and the transformation was astounding!

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[JimMcMillan]

Have you checked the governer/mixture control
(the large domed nut on the timing case) 1 turn on this has dramatic effect on the speed of the engine.

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[poggy]

Hi,

I have the same engine is a similar sized boat (Gib'Sea 76) and we had the same problem. When we first got the boat we achieved 6Kts and then is dropped to 3kts sometimes. I changed all the filters, fuel and air, put fresh fuel in. At full throttle we got lots of black smoke and dirty colling water (unburnt fuel). The fault just seemed to disappear one day, but then came back on Sunday. We stopped at a Marina and I took the covers off to see if I could see a problem. Anyway we tried it again at full revs and it seemed to come alive again. We then went out for a sail and it was fine all the way back. I can only assume that there was air starvation as with the covers off that day it ran 100%. The air vent pipes do run a long way though the boat and the cockpit locker, they also get squashed sometimes by the dinghy etc. We also had a habit of leaving the covers off sometimes, so this is why it felt intermitent.

The other key indication was that it ran fine for the first few mintutes while it warmed up and we came out the marina. I suppose that during this time it was using up air in the engine bay.

I am still not convinced it is this, but it all points to it. I would have thought the amount of oxygen used by a 1Gm10 would be tiny, but maybe it does use more than you think.

Anyway worth a try.

Poggy


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[wiggy]

i also have a Spring at Itchenor and had similar problems I know you say that the hull is clean but the wing keel is a great spot for crustatuions to grow on top mine had about 3cm thick all over at one time and in certainly isnt fast. What is thte name of your boat and hwere abouts do you keep her?

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[Ranger]

I have had a similar problem develop with the same engine on my boat. I believe that my problem is fouling on the keels and/or prop as they have not been cleaned for 6 months.

Mine revs freely in reverse without any smoke or fuel from the exhaust, but in forward gear I assume that the engine can't overcome the extra work it has to do, as the prop is more efficient in that direction.

I would have thought that if your problem is due to lack of air, it would not rev as high in reverse gear (as air digested is related to revs I assume). Have you tried reverse to see if you still have smoke or unburnt fuel from the exhaust? If you do, then I would agree that its probably an air / exhaust flow problem.

Best of luck,

Laurence



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[spring]

Thanks to everyone for your suggestions, my Spring is called SPRING WIND she is moored at Bosham. Sorry for delay in replying


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