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-   -   Yanmar YSB8 issues (http://www.sailnet.com/forums/gear-maintenance/23299-yanmar-ysb8-issues.html)

oft 09-23-2006 11:30 AM

Yanmar YSB8 issues
 
Iíve had a few issues with the 1976/77 Yanmar YSB8 on the boat I bought this June. The surveyor insisted that I replace the plastic tank that had been used to replace the original metal under the cockpit floor (evidently the plastic tank was too close to the engine to meet code). Anyway, I was going through the old fuel in the plastic tank while waiting for over a month for my new tank to get finished. With about 3 gallons left in the tank, I went out on a particularly rough day. Upon my return, as I put in her reverse (at idle speed) to slow down at my slip, there was an large puff of black smoke. The exhaust was already running black so I figured I was into some bad, old diesel and it would be best to wait for the new tank and fuel filter. I did.

The following were replaced: the tank, the fuel filter (with a Racor 120AS), and the fuel lines to and from the filter. The mechanic drained the old tank in the process and the Ďfuelí smelled more like turpentine than diesel. He said it must have been several years old to smell like that. I also suspect that the previous owner didnít top the tank up in the winter. Anyway, with the new tank, new fuel (after reading a fair amount I went with a 20% biodiesel/80% diesel blend), new filter and new lines, everything seemed to be great. The exhaust went from black to mostly clear. If I put the throttle forward it would put out a bit of white exhaust and then return to clear fairly quickly. So, everything seemed good.

To get from the slip to sailing typically involves only about 5-10 minutes of motoring. The other day, maybe the 3rd time out since the new tank, etc., the wind died and we motored back for about an hour. In the process, the oil indicator started to flicker. Besides that, everything seemed to be running well. The next day I checked the engine when it was cool and found that the oil level was below the lowest point on the dipstick. (The oil had been changed in June so this mechanic didnít check it, however, we did notice an oil leak.) It took 1L of oil (out of 1.7L total capacity) to get to the mid way point on the dipstick. I took her out for a great dayís sailing and for the 10 minutes out of the marina the engine ran great (little exhaust, etc.). She also seemed to run great the whole way back until I put her (again at idle speed) first in neutral to glide down the dock into my slip and then into reverse to stop. For this minute or so she started to put out a fair amount of white exhaust and there was a slight burning smell reminiscent of barbecued steak (someone in the marina might very well have been cooking but I donít remember smelling anything after the engine was shut off). When I opened the engine compartment afterwards everything looked and smelled fine.

Could the large amounts of exhaust (constant large amount of black exhaust with the old tank/fuel and now the recent 1 minute episode) somehow involve an internal oil leak and/or the engine burning oil? I recognize that the external oil leak somehow needs to be fixed if itís draining 1L of oil in 4 months, but Iíd sure appreciate any insight/ideas into what to do about everything else.

Thank you.

Gary M 09-23-2006 12:34 PM

If you are seeing white smoke, is it water vapour? do you have a good flow of water out your exhaust? Perhaps your water pump is not working properly.

The black smoke could just be old build up in your exhaust hose. I am planning on replacing mine this year and cleaning out the exhaust riser. Any restrictions in these will reduce the engine power.

Good luck my last boat had the same engine and I loved it. Always started even in below freezing temperatures.

oft 09-23-2006 03:20 PM

I forgot to mention that I also replaced the muffler and exhaust line recently. That didn't stop the black smoke but the new fuel tank, filter and fuel did stop it. Now I just get white smoke -- usually small amounts until the other night. The boat does have a good flow of water out of the exhaust so I don't think that's the problem.

cardiacpaul 09-23-2006 03:51 PM

the ranger rick secret decoder ring exhaust smoke color wheel says...
white smoke = water...either vapor, or cooling jacket)
blue smoke=piston rings
black smoke=fuel

this rings true for gas or diesel engines

camaraderie 09-23-2006 06:03 PM

First...loss of oil is an issue. If you are not seeing a lot of black smoke AND ont seeing it in your bilge, then it is being pumped out in liquid form through your exhaust hose. Logical suspect would be the oil cooler or transmission cooler with a small leak.

Second...white smoke = vapor as CP says and it happens when you are under way rather than at the dock so I would check for restrictions in your water intake line, blockage in your exhaust elbow or heat exchanger.
What is your temperature gauge reading when you start to see the smoke? Is thermostat working?

Rockter 09-23-2006 07:54 PM

I trust it is starting OK? If so, you would have reasonable compression.

Black smoke is normally a sign of the injectors over-delivering fuel.

Oft.... if your oil pressure warning is flickering, you really must stop.... your engine has not got long to live if that wee light is on.

oft 09-24-2006 03:56 AM

The engine starts immediately so the compression seems good. Also, I have added 1L of oil to get to the midpoint on the dipstick so there is no more warning light.

I don't have a temp guage only an overheating indicator light, but it is not coming on (the lights work because they flash on when I stop the engine) and the engine is throwing out a fair amount of water (it's raw water cooled). Interestingly, the white smoke does not appear to be an issue going out when the outside temp is still quite warm (~ 18 degrees C). I ran it at the dock for a while today and it seemed to run cleanly. It is only when I'm coming back and it is cooler that is seems to be the problem... Um, as I write this it occurs to me that at this point in the year there is enough moisture in the Vancouver air at this time at night (7PM) for condensation to appear on the coachroof. Could it just be that the 'white smoke' is the heated exhaust interacting with the water vapour in the air? (If so, maybe that's a problem with being a new boat owner... you hear horror stories and then when something happens you assume the worst instead of just considering the obvious).

yotphix 09-24-2006 04:49 AM

You might be onto something there Oft. The othe day here in SoCal we had a Vancouver type day with moisture in the air so thick you could drink it and I noticed white "smoke" from a little honda outboard that hadn't appeared before (or since). Cars do it too in cool moist weather. Take a look at other boats around you and see if they are being followed by the same white cloud.


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