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Black carbon soot from exhaust and on plugs

G

georgeinbeverly

Contributing Member
Mechanic says its not the carb

Mechanic says its not the carburetor ...
wants to change the intake manifold..
has not fixed the problem yet

Compression check mechanic says is 125
all around OK

any comments
 
"I also have black soot coming

"I also have black soot coming out of my starboard engine. It only happens when I first start it, but not everytime. I had the carbs rebiult about a year ago. Do they need adjusting or am I looking in the wrong area?"
 
Might be the chokes are set wa

Might be the chokes are set way too rich. I set might way lean and pump the throttles as necessary at cold start up.

Jeff
 
"That would make sense. At co

"That would make sense. At cold start, I barely have to pump the throttles and it fires up. I have electric fuel pumps. Can you give me a heads up on which is the choke?"
 
"Are you talking about after t

"Are you talking about after the engine is warmed up? Is it overloaded, does it turn the max rpm it's supposed to? Is the timing advance working?

Dan"
 
It does seem to happen after t

It does seem to happen after the engines are warm and then set for a short period of time. As far max rpm. they both top out around 3200. I do not know if that is max or not. How would I know if the timing advance is working?
 
"Use a timing light. Hook it

"Use a timing light. Hook it up to # 1 cylinder, then buzz the motor to about 3,000 rpms. The mark should move at least an inch, then come right back as you drop her back to idle speed.

My Edelbrocks have electric chokes. Let the boat sit about 5 minutes and they start to close down--and the motor is still fully up to temperature. That creates a rich condition at start up that takes extra cranking. The old Carters used a different system and didn't do that nonsense--their only good feature.

Jeff"
 
"On My engine the Soot was cau

"On My engine the Soot was caused by a bad Camshaft , The Lobs were almost completely
gone and perhaps causing to rich a mixture
when valves were not opening or closing
Removed the intake and I eye balled the cam
what a sad Site ..."
 
"You are nowhere near the rate

"You are nowhere near the rated RPM and that's why you have soot. I think it's 4000 rpm but it's been a while since I have had my manuals out. Check the timing advance like Jeff said. If they are tuned correctly you are probably overpropped form gaining weight, drag or the engines getting tired.

Dan"
 
"Here is what I do know. The

"Here is what I do know. The props are the original props. I had some work done a few years ago and the year was engraved. Does this mean anything?
With three guys, 3/4 of a tank of gas, here are some speeds I got a few weeks ago form a handheld GPS.

1500 RPM - 9MPH
2000 RPM - 10 MPH
2300 RPM - 13.5 MPH
2500 RPM - 16 MPH
2800 RPM - 20 MPH

She had more but I didi not push. I will this weekend.

The boat is a 1974 Trojan F-32. The timing advance makes sense. I generally see it after I have been cruising arond and shut it down for a short period and then when it is cranked up I get the "soot". I will top her out this weekend and look at the choke. Thansk for your time."
 
"Over the weekend, I ran her p

"Over the weekend, I ran her pretty hard, saw very little "soot" on one occasion. My RPM 's only got to 3300, however, on both enegines. It would seem to me that it is the pitch of the props since they both ran idenitical. She is running very well. Do I do anything about the RPM's. They are LM318 Fury 210."
 
"Did you do the one engine at

"Did you do the one engine at a time run up to check its max rpms? If not, just one motor can be sluggish, which pulls down the other.

Jeff"
 
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