1-cylinder Yanmar Issues

[agg212]

Hi all,

I've been having some issues with my Yanmar YSM12 (1 cylinder).

The symptoms are as follows:
- Has always been difficult to start
- When under load (forward/reverse): grey smoke in cabin, black exhaust overboard, dies when brought back to neutral, clapping/slapping sound as cylinder thumps
- In neutral, seems to run mostly fine

I've already done the following:
- replaced exhaust eblow/manifold
- checked thermostat
- good waterflow overboard
- checked impeller and looks fine

 

[sail sfbay]

Consider reaching out to a marine diesel engine mechanic?

 

[Davidasailor26]

grey smoke in cabin,

Well that shouldn’t happen. If you’ve replaced the exhaust and still get smoke in the boat, I wonder if part of the problem could be excessive blow-by causing smoke out the crankcase breather? Maybe try a compression test. Black exhaust suggest incomplete combustion, maybe bad injectors or airflow?

 

[kloudie1]

Check valve clearance before doing anything else.

 

[Benny17441]

Difficult to start: lack of compression or the starter cranking slow. Black exhaust: bottom, prop or both usually fouled by marine growth. Gray smoke in cabin: probably there is an oil leak which burns with the engine heat. Hints, make sure batteries are good and 100% charged. If the starter is cranking up to speed get an oil additive to thicken the oil. Thicker oil will increase compression and quiet down engine rattles some. Go ahead and clean the boat's bottom and prop. Adjust the valves lash. Make sure the fuel is good. If you perform these tasks and still continue having the same problems I would think the engine is done and in need of a rebuild. You seem to cencentrate on the cooling system; was there a recent overheat? Do change the oil after any overheat. Start the engine and remove the oil filler cap. Hover the palm of your hand over the opening, if you feel a large thump of air with each revolution that is air that needed to be compressed in the cylinder but escaped through worn piston rings. Some amount is allowed in older engines but if it is excessive it indicates a worn engine. Like I recommended heavier oil reduces compression leaks and can extend the life of a worn engine. Good luck.

 

[RoyS]

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