Yanmar YSB8 soot / exhaust prob?

[Denile]

Yanmar YSm8 soot / exhaust prob?

I have a 1978 Yanmar YSm8 single cylinder diesel, I just purchased not so long ago so I don't know alot of history. The two times I have been running there has been a black soot coming out of the exhaust, but it ran fairly smooth. Today I was out, ran it out of the marina (smooth) sailed for a couple of hours. when I went to start the motor it fired off yet started leaking exhaust from an exhaust clamp. I think there was excessive back pressure that caused this. the engine ran for only a few seconds and then failed to start.
There is a calendrical "muffler" right after the elbow, can this be the cause??
I would appreciate any feedback as to which direction to go.
Thank You, Steve

 

[Ameseys]

Hey Steve,

I just had my YSM8 rebuilt. I feel like the mechanic milked me for it over 6 months at 500, then 700 per month. In the end, the total was nearly $5000US. I was pretty mad - if I'd known the total, I certainly would have gone with a new engine. I had expected it to come in at half that price.

I have read that some boats can get a plugged exhaust. I haven't experienced that, but thought that maybe a chimney sweep could clean out the hose.

The waterlift muffler is a bear to get out, it is wedged so tightly in there. You can unclamp the hose from the after end and wiggle it loose. I had to remove the exhaust elbow to get the hose out of the top of the thing. Mine developed a leak I had welded up.

As far as black smoke, that usually indicates the engine is working too hard. Does the shaft spin freely? Is there growth on the propellor? Are you using the throttle too aggressively? Blue smoke usually indicates the engine is burning lube oil.

I suppose I would pull the after exhaust hose and reach into the muffler and hose with a long brush. See if it is sooty. Maybe reaching into the exhaust from the transom might tell?

Good luck, let us know.

Richard

I have a 1978 Yanmar YSm8 single cylinder diesel, I just purchased not so long ago so I don't know alot of history. The two times I have been running there has been a black soot coming out of the exhaust, but it ran fairly smooth. Today I was out, ran it out of the marina (smooth) sailed for a couple of hours. when I went to start the motor it fired off yet started leaking exhaust from an exhaust clamp. I think there was excessive back pressure that caused this. the engine ran for only a few seconds and then failed to start.
There is a calendrical "muffler" right after the elbow, can this be the cause??
I would appreciate any feedback as to which direction to go.
Thank You, Steve

 

[Denile]

Yanmar YSB8 soot / exhaust prob?/ Throttle adjustment

Richard thanks for the reply, after a short exam of the exhaust I found the noise I was hearing was coming from the head gasket. I guess I was a little too quick with my post. Anyway I tore into it and found that along with the breach in the gasket 2 of the water passages were completely blocked.
I ordered up all the necessary gaskets, did a quick grind and lap of the valves and put her back together.
The Yanmar runs well in the berth, I hope to take it out this weekend for the test drive under a load.
I do have a question on the throttle linkage.... as soon I attempt to put in gear, it throttles up. I feel that there should be a delay, so the transmission can get in gear.
I looked at the back side of the lever but nothing looked like an obvious adjustment. I was wondering if anyone else had the same issue?
Steve

 

[Ameseys]

I don't know about adjusting the lever, but you might look at the threaded cable ends. You can lengthen and shorten the ends there. Also, the cable mounts on the engine are grooved. You can loosen the screw and move the cable where they mount on the motor.

A helper moving the lever can reveal how the cables move.

Good luck - let me know what works for you. I want your ideas for my boat!

Richard