Trouble with Yanmar YSB8

[RICHARD READ]

I hope someone might be able to help me with this -

My Single Cylinder Yanmar YSB 8 horsepower engine has started throwing black smoke & sludge out of it's exhaust.

I am assuming this is excess uncombusted diesel. I am not sure how to go about fixing it. If anyone has had similar problems & can roughly describe what the cause/solution was I would be very grateful.

[Sonosailor]

Go to yanmarhelp.com

Not only can you post your problem and get excellent advice, but you can search their other postings for your particular problem and other issues regarding your engine.

I have done well there, since I know so little and need to know so much about my Yanmars.

[troppoboat]

G'day Richard it sounds like you have a bit of a messy problem on your hands thankfully Yanmars of your type are relatively simple and easy to fix. Essentialy black smoke is unburned fuel , there are a number of reasons for it. The least difficult, expensive and common cause of BS is partialy blocked injectors this causes the fuel not to be properly atomised and not burn properly. Removal of the injector is dead easy, remove the injector fuel line, bleed back fuel line and the two nuts securing the injector to the head and ease the injector out of the head. You will need to take the injector to a specialist to check, clean and calibrate. the other reasons for BS are lack of compression there are a number of ways compression can be lost the, main culprit is rings that are worn or cracked check the crankcase breather while running if a fair bit of gas is escaping then compression getting passed the pistons is more than likely the problem. only on a few occasions I have had valve problems with yanmars it would probably be worth checking the valve clearences anyway before tearing it to bits. I have worked on lots of yanmars over the years and have found them to be reasonably reliable and sturdy. Good luck and let me know how you progress. Regards Shane

Ps after you fix this problem you may want to check your fuel filter, a lot of fuel problems are caused by contaminated fuel.

[bmjpv]

I'm new to this forum but old with my boat. My engine intermitantly overheats at speed or tied to the dock. If I run it at aprox 2K in gear (today tied to the dock) it will run to 240F steadly. I've done everthing over the years and have had luck finding and fixing (inpellors rubber) but this one today calls for some help. I'm a newly retired auto shop owner but slight on the product knowlage. I need some fresh ideas, please! thanks, joe

[Alan Wheeler]

OK firstly Richard. Can we have a little clarification please. When you say black smoke and sludge, what is the circumstance please. Like as soon as you start the engine? or when under full RPM? or or or???
And what exactly do you mean by sludge. This is extremely important. Sludge in my English is a slimey gunk. Are you talking an gunky oil like substance? or just black carbon floating on the water???

bmjpv, Firstly, are you absolutley sure the engine temp is true to the gauge. 240F is very hot and the engine would be boiling. Is that actually happening??An answer to that would be good before I go any further.

[Tropic Cat]

Four most likely causes of black smoke

mixing elbow
fouled bottom
Barnacles on the prop
injectors

[Tropic Cat]

Joe

I think anyone would be hesitant to advise an autoshop owner about engine trouble!!! In any case, I'm a bit confused. I thought the 3QM30 was a raw water cooled engine. From the temperature reading you've given, this obviously can't be true any longer. Raw water engines operate at 120 to 140 degrees F.

If this is a fresh water cooled conversion, it could be anything. Start with the thermostat and head for the heat exchanger. If it's still raw water cooled, I'd say whoops.....

[nickc]

Had this problem with my Yanmar 3YM30 at 240 hours and 2.5 years.
Mixing elbow was partially blocked with carbon deposits. One hour to fix. The Yanmar dealer seemed to think that this was a normal occurance,
What annoys me about marine diesel engines is the problems we encounter and their frequency of occurance would just not be tolerated in the Automobile industry.

[Alan Wheeler]

What annoys me about marine diesel engines is the problems we encounter and their frequency of occurance would just not be tolerated in the Automobile industry.

If Automobiles had to work in the harsh enviroments and do the work that the Marine engine is asked of, then we would have to be a lot more tolerant in the car industry.

[GordMay]

Originally Posted by Alan Wheeler

If Automobiles had to work in the harsh enviroments and do the work that the Marine engine is asked of, then we would have to be a lot more tolerant in the car industry.

If pigs could fly ...
If boats were produced in simuilar number to automobiles, then marine standards and costs would be similar.
With an annual car production of about 34 - 40 million vehicles in the 1990s and well above 40 million in the 2000s, there were over 550 million automobiles in circulation in 2001 (how many thousand boats were there?).
In 2003, more than 2 million cars were sold in China alone.

[bmjpv]

Good to hear some much advise on my problem, thanks everyone. To make clear I have raw water to exhaust exchanger and antifreeze in block. I trust my electric temp gadge to be correct,when everthing is right it does run in the 110-140F range under load, the thermostat has be renewed.Since these thermostats are wax filled are they good for a really looooog time? or what? The clutless bearing was renewed 6 mos ago,bottom raw water inlet is good and flow inside of bildge out of strainer looks very good by popping of hoses at various places,Prop cleaned monthly (89deg water today) and I'm scratching my head. I like the Idea about the elbo at manifold (installed a new on 3 years ago but I'm gonna look, thanks everyone for the talk. joe

[nickc]

Alan,
I can't agree with you. Yanmars/Volvos and others are supposed to be designed for marine use and if I had the time to catalogue the problems that I have had over the last 13 years with 3GM30s and now 3YM30s with probably no more then 100 hours per year use then I would have to say they they are not fit for purpose.
I am an engineer in the Train manufacturing industry and our declared design life is 30 years and we have to guarentee over 70,000 km mean distnce between failures or face penalties. Thus we have to design for purpose.

[never monday]

Originally Posted by nickc

Alan,
I can't agree with you. Yanmars/Volvos and others are supposed to be designed for marine use and if I had the time to catalogue the problems that I have had over the last 13 years with 3GM30s and now 3YM30s with probably no more then 100 hours per year use then I would have to say they they are not fit for purpose.
I am an engineer in the Train manufacturing industry and our declared design life is 30 years and we have to guarentee over 70,000 km mean distnce between failures or face penalties. Thus we have to design for purpose.

Nick,
The design life is normaly quoted at 1000 hrs or 10 years. That is the standard the EPA in the US requires.

[nickc]

But Pat, 1000 hrs is only 41 days, if you are a fishing boat that's not much use.

[Alan Wheeler]

Yeah but if you are commercial and running that many hrs, you won't be using a 3xx30. Especially if your working 24hr/day, your a big boat with a big hard working engine. A little different to what we are talking here.
You are kinda right though Nick. But do you notice that most of the cooling issues on engines are with just the little ones. I think it is a result of the fact that a very small water flow is used on these little engines. And thus they tend to block in variouse places much easier. Big engines with big water flows don't have these issues the same. The other area that helps is the exhaust flow. The big engines are running big gas volumes and high temperatures. So the exhaust keep cleaner as well.
What I am meaning by the environment being hard on the smaller marine engines is that firstly they are asked to remain dormant for frequant long periods of time. Diesels don't like that. Then when they are running, they are often kept much cooler than what most engines desire. They are run at a constant load/rev range. Another thing a Diesel doesn't like. They like varying loads and revs. This isn't a matter of the engien not being designed right, it is a matter of the fact that it is a Diesel and it doens't like being treated in this way. But in saying all that, there is still nothing better.