My old Yanmar YSB12 diesel engine runs quite smoothly in relatively calm waters, but when the water is choppy and particularly if the boat heels, the engine runs rough and unstable, and the rpms sometimes go high for a while even at low throttle. Any ideas of what is going on here, and how this can be corrected? Thanks.
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Sounds like
Dave Dirty fuel in the tank getting into the fuel system. Check your filters, and find out, if you decide to do so, if your tank can be cleaned. Stu
Dave Dirty fuel in the tank getting into the fuel system. Check your filters, and find out, if you decide to do so, if your tank can be cleaned. Stu
How do I clean the fuel tank?
Stu, Thanks for the suggestion. Sounds like it could be the problem -- the boat has been sitting idle since last fall with a full tank of diesel. But we just changed the filters, and it still has the problem. Should I siphon out the fuel? How can I clean out the tank? Or is there some type of fuel additive that I could add to the fuel to help with this problem? Thanks for any suggestions.
Stu, Thanks for the suggestion. Sounds like it could be the problem -- the boat has been sitting idle since last fall with a full tank of diesel. But we just changed the filters, and it still has the problem. Should I siphon out the fuel? How can I clean out the tank? Or is there some type of fuel additive that I could add to the fuel to help with this problem? Thanks for any suggestions.
Fuel Polishing
Even with your fuel finter replaced, many fuel tanks have a small screen inside the tank. It can get glogged with crud over time. You can get professional folks at the marina to "polish your fuel/tank" essentially they filter out all the crud inside your tank. The cause? The fuel intake is usually slightly higher than the bottom of your tank, allowing crud to build up without getting sucked into your fuel line. This works for some time until there's enough stuff in there to get stirred up (heeling, rough seaway, etc. to become suspended & get into yout fuel intake. Then you get your symptoms. Time to polish. Good luck!
Even with your fuel finter replaced, many fuel tanks have a small screen inside the tank. It can get glogged with crud over time. You can get professional folks at the marina to "polish your fuel/tank" essentially they filter out all the crud inside your tank. The cause? The fuel intake is usually slightly higher than the bottom of your tank, allowing crud to build up without getting sucked into your fuel line. This works for some time until there's enough stuff in there to get stirred up (heeling, rough seaway, etc. to become suspended & get into yout fuel intake. Then you get your symptoms. Time to polish. Good luck!
Worth looking into
Thanks for the suggestion, which I think is worth looking into. However, I don't understand why my new fuel filters don't take care of that crud, and I don't understand why the engine sometimes races briefly at low throttle... also, there's usually some blue smoke in the exhaust when these problems show up... Are these symptoms all consistent with a dirty fuel problem? Thanks again.
Thanks for the suggestion, which I think is worth looking into. However, I don't understand why my new fuel filters don't take care of that crud, and I don't understand why the engine sometimes races briefly at low throttle... also, there's usually some blue smoke in the exhaust when these problems show up... Are these symptoms all consistent with a dirty fuel problem? Thanks again.
might be something else too
What everyone else has suggested might explain the rough and unstable engine. However, the increased RPM might be something else. Is it possible that the engine control cables or the fuel shut-off cables are being pinched/stretched or the fuel line is pinched normally, but during rough waters/heeling the hull flex is changing the cable length or unpinching the fuel line? just a thought..
What everyone else has suggested might explain the rough and unstable engine. However, the increased RPM might be something else. Is it possible that the engine control cables or the fuel shut-off cables are being pinched/stretched or the fuel line is pinched normally, but during rough waters/heeling the hull flex is changing the cable length or unpinching the fuel line? just a thought..
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