My '78 S2 9.2a has probably the original motor in it - a YSM12 horizontal one-cylinder. It's about as primitive as they come, but serviceable. Yesterday we were returning from a daysail when the wind dropped. We proceeded to motor in with my fiancee at the helm. Things were running well, so she decided to push it a bit and see if we hit 4 kts. Just after she throttled ahead I saw white smoke coming from the stern. Then the motor started racing and clouds of smoke billowed from the exhaust. I told her to drop the throttle and kill the motor but it was too late, the little YSM was running away on motor oil. I jumped below, tore off the engine cover and tried to choke the intake. I reached in and shut off the fuel, and tried to choke it off some more, and finally the motor died. More than one boater rushed to our aid after seeing the smoke and thinking we were on fire, but I said it wasn't possible since it was a diesel. lol
We drifted along in flukey to no wind for an hour or so. At one point I started the motor but the temp alarm sounded so we shut 'er down. After another hour or so of cooling off I restarted and all seemed well, so we putted the rest of the way home at barely more than idle speed, for fear that it would run away again.
I had run the motor last year with no incidents of this type (just alot of air
bleeding). I changed the oil this spring and brought the level to the top of the dipstick. I'm thinking a combination of compression blow-by causing alot of flow thru the breather into the intake, along with a high oil level, as well as the high RPMS we attempted to run at caused her to pump motor into the intake and fuel the runaway motor.
Last night I drained off a cup or so of oil, bringing the level to 2/3 on the dipstick, which is where it was last year. Any thoughts, precautions, troubleshooting ideas? Is it time to re-ring? Add a secondary oil-catchment to the breather tube?
We drifted along in flukey to no wind for an hour or so. At one point I started the motor but the temp alarm sounded so we shut 'er down. After another hour or so of cooling off I restarted and all seemed well, so we putted the rest of the way home at barely more than idle speed, for fear that it would run away again.
I had run the motor last year with no incidents of this type (just alot of air
bleeding). I changed the oil this spring and brought the level to the top of the dipstick. I'm thinking a combination of compression blow-by causing alot of flow thru the breather into the intake, along with a high oil level, as well as the high RPMS we attempted to run at caused her to pump motor into the intake and fuel the runaway motor.
Last night I drained off a cup or so of oil, bringing the level to 2/3 on the dipstick, which is where it was last year. Any thoughts, precautions, troubleshooting ideas? Is it time to re-ring? Add a secondary oil-catchment to the breather tube?
