yanmar diesel

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kieronriley

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i overheard a conversation in our boatyard the oeher day concerning a two cylinder yanmar the owner has had lots of trouble starting it ,i knew the previous owner and he had problems but it would start.the new owner has discovered that the starter turns one way and the starting handle turns the engine the opposite way my wonder is could the engine be started in reverse and if so could this be why its an utter bu??er to start or is it that at some time in the past the dogs on the starting handle have been incorectly fitted Kieron
 
Apart from some very specialised big ship engines, I have never heard of a four stroke diesel engine running backwards, and don't think it is actually possible unless the camshaft has been changed.
 
My boat is fitted with a Yanmer YSE 12 and the hand start on that is anti clockwise which I find very difficult and somehow "un-natural". but may be easier for a left-hander. I think it is this way because the hand start drives a cog which in turn meshes with the crankshaft which actually turns clockwise. From memory Stuart Turners could be hand started from the gear-box end and this meant turning the handle "backwards".
Ted.
 
I know that the 1GM10 will run backwards - that is why you should always give it some throttle on starting to stop it doing so and destroying it's little self.
 
That's very interesting.
On one occassion my Yanmar 2GM seemed to falter, then start running very rough, not fast but very jerky. I suspect the prop hit some debris.
I whipped open the hatch and the engine was blowing smoke and dancing fit to bust, and running backwards. I hit the stop button very fast.
I checked, but could find now obvious faults so re-started and everything worked OK.
I've never dared mention this to anyone in case they thought I was hallucinating. I later wondered myself if I really saw what I thought I had.
 
[ QUOTE ]
I know that the 1GM10 will run backwards - that is why you should always give it some throttle on starting to stop it doing so and destroying it's little self.

[/ QUOTE ]
That's frightening - I didn't know that - do you know what causes it to start in the wrong direction? And will it be trying to suck air in from the exhaust and blow it out of the air cleaner? And I thought all I had to worry about was the pump impeller!
 
I have tried several times to hand start my 1GM10, but have never managed to keep it going through the compression as the compression lever is lowered. One fine day I tried it when the engine was warm. As the lever dropped the piston hit the compressed gas, bounced back, and the engine started in reverse. The cabin filled with black smoke very quickly! It subsequently ran fine on a normal electric start.

A little later I found some bits of blackened foam. Lesson learned - if you ever manage to run your Yanmar backwards, check the foam air filter before you run it again - it does not stand up to exhaust gas, and the bits that go down the air intake probably don't burn as well as diesel!
 
Dunno - never happened to me but was a tip from Yanmar's European Service Manager. Apparently the little rascals will start quite happily with no throttle (in either direction) - but, apparently, if you give it at least half throttle while cranking it will not happen, therefore no need to be frightened.
Other interesting tips from the same guy :
1) The oil filter specs are different depending on type - e.g industrial version is different to marine (believe it if you want /forums/images/graemlins/smile.gif )
2) Top cause of engines needing rebuilds is bore glazing due to excessive running on light load. They are designed to run for years at their full rated output and the best way to kill it is to use it on light load e.g. charging the batteries.
3) Check the exhaust elbow regularly for perforation of the inner sleeve as once this has corroded you will soon need a new cylinder head.
 
I have heard of old brit motorcycle engines running backwards, if you have ever tried starting one and it kicks back you will know there is enough energy there for the engine to rotate in reverse. but i cannot comment on diesels.
 
I used to have a Yamaha 175 trail bike. That would run backwards quite happily.

With a bit of practice you could ride round the garden backwards.

Any 2 stroke will go round either way.
 
With a diesel the fuel is injected directly into the cylinder head (or swirl chamber) which at idle is as near as dammit TDC so will run backwards, in which case it will be exhausting through the air filter which cannot take it and will probably disintegrate but at least it is replaceable. What's more serious is that it is drawing combustion air through the exhaust , which will contain water. If a large enough volume of water is drawn into the cylinder then this can create a hydraulic lock which will not compress. The effect is that the rising piston will hit a solid block of water and come to a sudden halt. This can result in serious damage to the engine, normally a bent con rod, but could damage engine mounts.

If you find your engine running backwards, stop it immediately. Provided it's only at tickover it may not draw in sufficient air to suck up water and if it does then damage may not occur. Do not attempt to speed it up or you may have a very big repair bill.

A 2 stoke petrol (or 2 stoke diesel - very few about) will run in reverse, A 2 stroke still draws through the intake and exhausts through the exhaust whether it runs forwards or backwards. The only difference is the timing of the spark. At low revs this is usually near TDC. The old Bond 3 wheelers did not have a reverse gear so to reverse you had to stop the engine and re-start it in reverse; the ignition timing and starter motor connections were reversed accordingly from inside the car. It would then go just as fast backwards as forwards - and with all gears!

A four stoke petrol engine will not run in reverse because there will be no fuel supplied to the combustion chamber, this is because the air flow will be backwards and the fuel is supplied to the inlet manifold either injected or by a carburettor.
 
Let's get a few facts straight.

2 stroke engines can run in reverse. If it is a simple petrol engine, this can happen as the spark is almost at TDC (piston is at top dead centre). A diesel ignites the fuel by the heat from compression, so the fuel is injected into the cylinder long before TDC is reached, usually 14 to 22 deg. As long as fuel is present when the piston is on a compression stroke, the engine should fire, even if the fuel has been injected on the downward, instead of the upward stroke.

So a 4 stroke diesel will run in reverse, just the same. It just won't use the fuel as efficiently.

The reason some diesels race flat out is that when running in reverse, the type of govenor fitted to the engine is working in reverse i.e. it is delivering the maximum fuel all the time. Diesel engines are govenerned by the amount of fuel only, whereas a petrol engine is governed by the amount of fuel/air mixture.

This is not the same a a runaway, where a worn engine can run on the sump oil getting past the piston and into the combustion chamber.
 
The Dolphin 12 marine 2 stroke in its earlier versions was designed without a gearbox so that reversing meant stopping, and restarting in the opposite direction. It had a special starter designed to start it either way.

Owners grew prematurely grey at all the stopping and starting involved in close quarters manoevering! There was always that heart stopping moment - will it, wont it??!!!

Nowadays they are built with gearboxes, but the engine will apparently still run backwards quite happily.
 
you do rotate the starting handle in the oposite direction to the crank, it goes through a series of gears in front cover as far as i know.
If you see the owner again tell him to try running the engine(when it does) on each cylinder in turn to see if one runs badly
 
I recall a couple of our local fishermen talking about a former collegue who's engine ran backwards for years. He was so convinced that it was right that he got a new prop. made - so that the boat went forwards! If I recall, it was a hand start that had such strong compression that it would "bounce" back and keep running. He thought thet was what it was supposed to do. Years later, an engineer spotted a timing error, and the engine would run the "right" way!
 
[ QUOTE ]
I have tried several times to hand start my 1GM10, but have never managed to keep it going through the compression as the compression lever is lowered. One fine day I tried it when the engine was warm. As the lever dropped the piston hit the compressed gas, bounced back, and the engine started in reverse.

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Yowzers! I can hand start my 1GM10 from about april-october, it's a question of technique! never had it bounce hard enough to start backwards tho. in fact now I think about it that's really weird, because it would have to have enough energy to go through almost a whole rev and then through the compression... summat odd happened to you, chum! incidentally, the knowledge that you can start your engine independantly of a battery is quite reassuring...
 
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