My YSM 8 Diesel

[alturaam]

My YSM 8 on my 25 MkII here in Annapolis was worked on recently. An exhaust elbow was replaced and the idle was adjusted.

WHen I run the motor while tied up, after warming it up for 5 minutes or so, I put in forward and reverse for very brief periods, just to check that the prop engages.

I end up with some white smoke in the exhaust (which the manuals say is OK, under load) and some black fluid coming out of the same exhaust. Not sure if this is oil or partially burnt fuel.
The black stuff leaves marks down my transom.

Is this normal when the prop is engaged and is slightly straining while the boat is tied to the slip?

My diesel mechanic wants to check the boat (a quick haul out) for a fouled prop. While I trust my guy, I saw this boat before it went into the water in late Feb. The cutlass bearing had a little play in in it when it was surveyed but other than that it looked fine.

 

[Boffin]

slightly white smoke is normal , but I once put too many lubricate oil in the engine , excessive white smoke came out , it indicated the lub oil go into the cylinder , may be thr. the cylinder ring. If the pro was fouled or overpowered , the carbon in the smoke will mixed up with the cooling water and it looks like a back water , but you can still see the carbon floating in the surface .You have to check the fuel nozzle .
If the back water is in oil base that is the lub oil go into the exhaust system.

 

[jnovie]

slightly white smoke is normal , but I once put too many lubricate oil in the engine , excessive white smoke came out , it indicated the lub oil go into the cylinder , may be thr. the cylinder ring. If the pro was fouled or overpowered , the carbon in the smoke will mixed up with the cooling water and it looks like a back water , but you can still see the carbon floating in the surface .You have to check the fuel nozzle .
If the back water is in oil base that is the lub oil go into the exhaust system.

If you do decide to check for a fowled prop it would be far less expensive to have a diver inspect the prop rather than haul out.

 

[Syntonos]

YSM8 common (diesel) mistake

Sound advice from Boffin & jnovie.
If the black stuff out the exhaust is sooty and lies on top of the water your overloading the engine. Back off the rpm and see if it cleans up. Your engine is more akin to the old movie "African Queen" in performance. CHUG Chug chug. The best my boat does under power is around 5 knots (hull speed). Relax and enjoy the ride. Remember you have a solid IOR formula SAILboat, Not a modern Light Displacement racer.

Check to make sure the prop isn't fouled (jump in the water with a knife-save $$$) then take it out for a drive, watch the exhaust, it should puke water occasionally. Look for the soot, then back it down and note your speed. Your ears will come accustom to the proper tone.

 

[alturaam]

Thank you all Syntonos, Boffin an Jnovie. I think all of your diagnoses have been accurate. I will meet up with my Yanmar mechanic tomorrow at 8AM before I drive off to work, start the motor and demo everything to him. I was getting black sooty stuff being puked out the back along with water, that is, when I engaged the clutch to go forward or backward while tied up in the slip, a few seconds at a time either direction. I guess that is enough of a load for the motor to be working hard and puking black. My exchanges with the mechanic are such that he wants to make sure that the prop is not fouled. It isn't, that I know because the boat was just placed in the water in late Feb. How much growth could there be? He is concerned that my motor might not have enough reserve power and that is might be dealing with some resistance. Like all of you, I do not want to haul the boat out (expensive) and a hassle, time wise. I want to drive this thing out the slip and raise the sails, period. I have watched youtube videos of a Japanese Yam 25 owner and listened to the sound of the motor. It is a chug, chug, chug just like you described it, Syntonos.

Sound advice from Boffin & jnovie.
If the black stuff out the exhaust is sooty and lies on top of the water your overloading the engine. Back off the rpm and see if it cleans up. Your engine is more akin to the old movie "African Queen" in performance. CHUG Chug chug. The best my boat does under power is around 5 knots (hull speed). Relax and enjoy the ride. Remember you have a solid IOR formula SAILboat, Not a modern Light Displacement racer.

Check to make sure the prop isn't fouled (jump in the water with a knife-save $$$) then take it out for a drive, watch the exhaust, it should puke water occasionally. Look for the soot, then back it down and note your speed. Your ears will come accustom to the proper tone.