Yanmar Woes

[Charlie]

The access to my engine is not horrible but yours is fantastic. I'm jealous.

[meyermm]

I am not quite comfortable with the idea of these Yanmars. The very high specific output -- 50 horsepower per liter -- is the same as my first BMW, considered a pretty high performance gasoline engine at the time (admittedly years ago). That just doesn't seem right for marine use. By contrast, the three cylinder diesel in my genset (also a Yanmar) puts out only 14 horsepower out of 1000cc. At 1500RPM. I like that. I like that a lot. That's a marine approach to power. Yes, I would prefer the Perkins.

Four cylinder engines fitted to most cars these days have the power of very highly modified race engines of twenty or so years ago. They rev their heads off and have a much longer life than older road engines. Not sure what it is like where you are but here in OZ many engine reconditioners have closed down over the last ten years simply because there is no work due to reliability and long engine life. Just because it is in a boat does not change things much, your boat engine operates more like a stationary engine than a car or truck engine. You will find that Yanmar's first recommendation for oil is a monograde oil but no one takes any notice. The reason is it is less prone to bore glazing from running the engine in a no load (battery charge) condition. Block design + changes in material + better machining tolerances have negated the need for big heavy engines, boat anchors as I refer to them as.

[bstreep]

Hey, just catching up on this.

For Racor 500 units, there's a "donut" that needs to be fitted to older units - if there's no donut, you don't filter.

[MitchM]

i think that yanmar does not recommend running at more than 17 degrees heel is two fold: (1) ineffective splash lubrication at greater angels and (2) operating at higher angle of heel increases possibility of engine 'runaway'....

you also stated '... I looked in the engine compartment and nothing seemed amiss, but the coolant level was down somewhat. I topped it off..."

how much coolant did you have to add , and did you notice increase in operating temperature (if yyou ahve the C panel with temperature gauge on it that is)


be interested to hear what the verdict is on your mechanic's exhaust manifold crack theory. hard to imagine the scenario for bad running turbo, loss of antifreeze coolant form a closed system AND coolant blowing out in the exhaust gases.

if you are in england find david swain, a top notch yanmar engineer. pm me and i'll email his contact info ..

[MitchM]

"The oil was overfilled. I removed half a liter of oil to bring the level down."""

that may explain the entire poor-running scenario...

yanmar's GMs and JH's are splash lube engines. this means that in addition to getting lube oil forced to the cylinder walls from the oil pump, this engine is also lubricating its cylinder walls by "splash lubrication," meaning that oil from the pan gets splashed up onto the cylinder walls when the engine is running. overfilling the splash-lube yanmar engines with oil is is VERY BAD . in this engine design , the oil in the oil pan splashes up to lubricate the cylinder walls. the engine would much prefer to burn pure diesel with a proper air mix in its cylinders. with adequate lubrication of the cylinder walls from splash lubrication (ie the right amount of oil in the pan, measured on the dipstick to the 'full ' mark) the diesel fuel to air mix is fine, and the diesel burns properly . when the oil is overfilled, there is excess oil in the oil pan. too much oil then splashes into the cylinders, and too much oil in the cylinders will adversely affect the ability of the engine to combust the diesel fuel it is trying to burn. as a result of overfilling the oil in a splash lube engine your engine will now have to burn off that excess oil (unless you the owner take the excess oil out...).with too much oil in the pan, your fuel to air mix out of the injector is NOT set to burn this extra bunch of lube oil splashing up. so now in every power stroke of a given piston, there is extra lube oil on the cylinder walls that will either be combusted up with the diesel, or will drip back down into the oil pan. combusting too much splashed up lube oil in your cylinders will give black smoke and rough running. )so your poor engine is trying to burn the diesel using its known air-to-fuel ratio as set by the injector pump, but its precision fuel-to-air ratio coming out of the injectors is now not working as well because there is excess oil splashing up which the engine has to combust . so the engine runs rough or not at all, until the excess oil is gone. so GET THAT EXCESS OIL OUT!! then your engine should run fine.
note also that how much oil is splash lubing is a function not only of the amount of oil in the oil pan available to be splashed, but also of the angle of heel of the boat. a steep heel makes more oil slosh up from the oil pan. an overfill of lube oil combined with a high degree of heel say over 17 degrees can lead to a very dangerous situation called ENGINE RUNAWAY. in this scenario, so much lube oil will splash onto the cylinder walls and be combusted that the engine RPMS suddenly shoot very high 4000+, you are now burning lube oil and diesel, the engine sounds like it's screaming, black smoke is pouring out, the more you heel the more you suck lube oil in and you can quickly destroy the engine. the remedy is immediately bring the boat to flat zero heel and drop the throttle to idle 800 rpms and hope to hell the runaway stops. you hope that these maneuvers brings rpms back to normal, because you CANNOT shut down an aluminum engine running really hot using the stop solenoid or emergency button. yanmar recommends idling your eninge for 3 to 5 minutes before shutting it down rapid immediate shutdown of a hot engine can seize the piston to the cylinder wall, then possibly bending a connecting road, scoring your cylinder walls, warping the head, and other bad things...(well that's another thread we can start called YANMAR ENGINE RUNAWAY.. would you like to see some nice pictures i have of a bent con rod, scored cylinder, etc...not good. (and not my engine ..) )

you did not do an engine runaway to your engine . that's good...everything should be fine after you remove the excess oil.

moral of the story might also be : (1) check the companion thread on this forum on how to not 'overfill your yanmar' with oil when you are changing the oil and ...(2)
get a different mechanic..?

[meyermm]

Please do not write an engine manual as it will drive me Banana's your post was enough.

[dial_amonkey]

Originally Posted by delmarrey

Just one last picture so all can see for them selfs...............


.

I had wondered if the Yanmar check oil level notification/sticker means "Check oil level AT LEAST 10 mins after shutdowwn" giving time for the oil to return to the sump - less so ONLY check the oil level 10 mins after shutdown?

But might be that is the only time the dipstick is accurate

[Wayne Bostow]

Can anybody comment on the vaguries of diesel fuel, especially changes since 1970 or so. Do we need additives for engines over twelve years old? What is "polishing"? How can we clean the tanks?