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mike pahl · 23-01-2015, 09:31

My 15 hp Yamar is putting out a sheet of sut. what would cause this. I have changed all fuel filters and still having the same problem.

gonesail · 23-01-2015, 09:42

if you also see steam coming out the exhaust then check the mixing elbow if it has not been replaced lately .. it is usually a problem.

Cheechako · 23-01-2015, 09:55

what's sut?

mike pahl · 23-01-2015, 10:07

Soot (carbon)

darylat8750 · 23-01-2015, 10:18

Check that there is no restrictions in the airflow. Both intake and exhaust. As mentioned it is most likely near where the cooling water is injected into the exhaust.

Sailmonkey · 23-01-2015, 10:24

Or the prop is dirty or somehow harder to turn and the engine is overloaded.

leftbrainstuff · 23-01-2015, 10:24

Without specifics start with FACT. Fuel, air, compression, timing. I'm assuming it ran well and you haven't changed anything since. I'm also assuming power, revs, operating temps, oil level and condition is all ok. These are your pre start or running checks.

You've changed fuel filters but are all injectors delivering fuel and with a good pattern? Is the fuel injection pump delivering the right amount of fuel?

Intake doesn't sound like it's an issue. Is your raw water discharge pattern the same as before?

Compression and timing I'll assume haven't changed.

FACT or FACTS (spark) for gasoline engines is the universal diagnostic checklist.

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mike pahl · 23-01-2015, 10:59

Engine starts ok, So my compression is ok. Timing I don't know. Do not know how to check it. I do not have any glow plugs so I know the compression must be ok or I would have a hard time starting.

mike pahl · 23-01-2015, 11:04

How can I check injector pattern?

meridian28 · 23-01-2015, 11:09

What year? 2-stroke or 4-stroke?

Cheechako · 23-01-2015, 11:11

OK... soot... I'm guessing the exhaust elbow restriction..... or something wrapped on the prop...

Suijin · 23-01-2015, 11:13

How clean is your bottom and the running gear? This problem always comes up in the fall, at the end of the season, when props are heavily fouled and as mentioned, the engine is overloaded.

I would start by checking the mixing elbow and confirming that it's not constricted with carbon before I messed with the injectors. To check the pattern you're going to need a rig for pumping fuel through them at the rated pressure. Probably easier to hire a mechanic if you don't know what you're doing. It's not a costly exercise, particularly if they can do it right where you are.