M25xp - Grey smoke, unburnt fuel in exhaust

[kurt]

Thanks Ron and Ken.  That is on the next steps list.  Did some more symptom checking though today. 

Boat idles to 3100 fine.  Reverse at dock 2400 max and fuel in exhaust as before.  Removed k&n airfilter - no impact to symptoms.  Screwdriver to ear on the 3 injectors and they all sound the same.  Noticed air filter was black with what appears to be oil or fuel.  Was red not too long ago.  Now thinking exhaust may be restricted causing too much back pressure as another potential cause?  Elbow is only 6 years old - muffler and exhaust hose original.  But cooling water seems to come out the back fine.  Or does fuel in an air filter also arise with any cause of unburnt fuel including injectors?  Maybe I am grasping at straws. 

Kurt

[KWKloeber]

Thanks Ron and Ken.  That is on the next steps list.  Did some more symptom checking though today. 

Boat idles to 3100 fine.  Reverse at dock 2400 max and fuel in exhaust as before.  Removed k&n airfilter - no impact to symptoms.  Screwdriver to ear on the 3 injectors and they all sound the same.  Noticed air filter was black with what appears to be oil or fuel.  Was red not too long ago.  Now thinking exhaust may be restricted causing too much back pressure as another potential cause?  Elbow is only 6 years old - muffler and exhaust hose original.  But cooling water seems to come out the back fine.  Or does fuel in an air filter also arise with any cause of unburnt fuel including injectors?  Maybe I am grasping at straws. 

Kurt

Where does your crankcase breather hose run to?   To the air intake -- is that the source of gunky KN?
Is the oil ok, level normal - ie, no fuel diluting it (leaking injector pump pushing fuel to the crankcase)?

Ken

[kurt]

Ken,

Breather tube runs down to oil absorbing pad under engine.  Silver dollar sized black mark to where the tube blows.  Oil engine level was perfect when I checked it when this symptom first arose.

At this point, I think I will check exhaust, then check injectors, then replace injectors or then have someone replace/rebuild injection pump...

Kurt

[Stu Jackson]

Kurt, consider using the fellow in Oakland that helped Dave Sanner:  http://www.c34.org/wiki/index.php?title=Rebuilding_the_M25-XP

[kurt]

Bingo.   Just pulled hump hose and exhaust riser is blocked right in front of the place where raw water injects. 

Time to pull the 6 year old riser and either clean or get a new one.

Thanks again for everyone's help.

Kurt

[KWKloeber]

Bingo.   Just pulled hump hose and exhaust riser is blocked right in front of the place where raw water injects. 

Time to pull the 6 year old riser and either clean or get a new one.

Thanks again for everyone's help.

Kurt

Bingo.   Just pulled hump hose and exhaust riser is blocked right in front of the place where raw water injects. 

Time to pull the 6 year old riser and either clean or get a new one.

Thanks again for everyone's help.

Kurt

Ahhh ha.  Cool (soon)!
So plenty of water flow, as you said.  I'm surprised that the engine would run well with the exhaust blocked.

if the riser is bad (6 years??) you might want to consider the Westerbeke water cooled-riser that I'm doing for two C30 owners.  It's a "project" but worth it in the end.

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Ken

[KWKloeber]

<<run well with the exhaust blocked.>>

Ooops,

I meant to say run at all with the exhaust blocked!!!

ken

[kurt]

Hello everyone,

I installed the new exhaust riser (from Catalina Direct) and the problem is solved/all is good.

The boat revs even higher now in gear - 3000 - with my 15x10 flexofold - whereas before it went only to 2850/2900.  Interestingly, maybe this riser is a bit less restrictive.  I did note that the raw water nipple doesn't extend as far into the exhaust pipe on this version.

Thanks for all your comments/help.

Kurt

[Noah]

Congrats!

[Ron Hill]

Kurt : Bingo.   Just pulled hump hose and exhaust riser is blocked right in front of the place where raw water injects.  Time to pull the 6 year old riser and either clean or get a new one.

Think that you need to look at the old riser and find out what the "stuff" is that caused the blockage!  Otherwise a 6 year old riser should not have failed or become clogged from normal use!?!  

Was it stainless or black pipe riser?, carbon buildup?

Keep us posted

[kurt]

Ron,

I hear you on that.  Engine starts/runs perfect with no smoke so think I'm ok on that front.

My theory is the raw water nipple extended a bit too far into the exhaust pipe which created a place for junk - carbon, salt etc to form.

Kurt