Yanmar 2GM intermittent low power

[Northeaster]

Ran my 1982 2GM (raw water coolerd) for a few hours today - off and on. Boat / engine is new to me, but in previous few short runs, engine had power. Today, ran great, then next time, started sluggish, vibtrated more, had low power, but then came out of it suddenly, with a poof of smoke and worked great again. Then happen twice more, but took longer to come out of it.

Seems like it may have been only running on one cylinder, or not getting enough fuel / something in the 2nd cylinder, until it came out of it. Was some white smoke at times during this.

Checked the racor filter / separator - Doesn't seem to be any water in it.
Can change the injector filter, but would this account for these symptoms?

Could one injector nozzle or spring be clogging / sticking?

Thoughts??

[rperret]

Originally Posted by Northeaster

Ran my 1982 2GM (raw water coolerd) for a few hours today - off and on. Boat / engine is new to me, but in previous few short runs, engine had power. Today, ran great, then next time, started sluggish, vibtrated more, had low power, but then came out of it suddenly, with a poof of smoke and worked great again. Then happen twice more, but took longer to come out of it.

Seems like it may have been only running on one cylinder, or not getting enough fuel / something in the 2nd cylinder, until it came out of it. Was some white smoke at times during this.

Checked the racor filter / separator - Doesn't seem to be any water in it.
Can change the injector filter, but would this account for these symptoms?

Could one injector nozzle or spring be clogging / sticking?

Thoughts??

how old is the fuel? how old are the filters? did you put in any diesel additive?

in my used/new to me boat - the fuel was ca. 2005. it ran fine - other than a leaking banjo bolt which I repaired. but when i put in new diesel - i could feel the difference in performance.

[Northeaster]

The fuel is at best from last summer - tank was kept full for winter storage. Reasonable maintenance was performed on engine each year - oil change, etc - done by marine yard. However, can't gaurantee that filter was replaced last year.

I definitley can / will change injector filter - however, I wanted thoughts on other possible causes that might affect only one cylinder, as well. I guess a dirty filter / dirty fuel could have caused either / both cylinders not to work properly - I am not sure if it was the same one causing the low power each time, or it may have been either / both cylinders affected.

If changing the filter doesn't fix it, I would like to know if I should remove / inspect the injector nozzle, etc next - or where to concentrate my efforts.

[Northeaster]

forgot to mention - I did not add diesel additives. PO may have, but I am not sure. I have over half a tank left, and could pump out fuel to containers, if necessary, but would like to see other options as well. Engine is 25 years old, but fuel tank has been replaced in approx last 3-10 years, as looks quite new.

[Northeaster]

today, changed the yanmar fuel filter (old one was spotless anyway), and primed the fuel system with the bleed screws on the fuel filter unit, and injection pump (using the small, manuel pump). Still ran bad. While it was running, loosened of both injector nozzle nuts (one at a time), which imediately caused the engine to work poorly both times (I think this rules out my running only / partially on one cylinder theory - as it was the same on both cylinders).
One thing confused me, - after I bled the lines to the injection pump bleed crew, I loosened the injector nozzle nut(s), but could not get fuel to them, by using the mauel pump. However, it still started OK. Is there a chance that air, or something would cause it to run poorly, but still start fine. It only has about 1/4 of the power it should - for example, the shaft and prop turn, but even when I increase the throttle, i barely / or really don't have enough power to move forward - against moderate wind - to my mooring ball. Yesterday, it would only do about 2 knots - running poorly, but would then easily do 5-5 1/2 knts, when it came out of it.

Could the old, stale fuel cause it to work badly for a while, theb suddenely work great for the next hour? Or would it not work somewhat poory all the time. There is no water in the racor filter / separator. I have not taken it apart, just drained a bit of clear fuel form the bottom.

Reading a couple of maneul, is there a chance that the governor, or something else is sticking?

Thoughts please!!

[puff6022]

sounds like a bad mixing elbow. How old is it

[Northeaster]

engine is 1982. I never thought to check the mixing elbow, as I thought that would cause continual problems. Could that cause it to work bad, then work great for an hour after that, as it warms up, or something like that?? I am defintely getting water out the exhaust, and no temperature alarm, either when it runs bad or good, for an hour or more.

[Rickm505]

You do have a fuel line type of problem.I think you diagnosed it correctly but you might want to check the primary fuel filter. Just follow the fuel line from the engine toward the fuel tank and you'll find it. I'd replace it. When we speak of filters this is the one that gets clogged first. Also, if it has a water separator, check the bowl for water, but unless you saw a lot a white smoke when she was running rough, water probably isn't the problem.

Rick in Florida

[Northeaster]

Would a bad mixing elbow account for the white smoke as well?

[Northeaster]

Rick - there is white smoke when it runs bad, and I increase the throttle.
I never took the racor apart, to check the condition - stupid of me - for some reason, I focused on the yanmar injection filter - there is no water noticable at the bottom of the racor, and I got clear, red tinted fuel, when I driained a bit from teh bottom.