Cat 3116 Diesels blow black soot on back of boat

E

Eagle Attitude

New Member
Sep 6, 2007
6
Louisville, TN
Boat Info
440 Express Bridge
Engines
Cat 3116
I have a 1995 Sea Ray 440 Express Bridge with twin Cat 3116 diesel engines. It tends to blow black soot over the rear of the boat. I have been told to blow it out when I am out and sometimes that works and there is very little soot. I took a trip this weekend and blew it out good, but the soot was worse than ever. Anyone encountered this and have any suggestions for a fix?
 
Diesel soot is a sign of unburned or partially burned fuel. The cause is most likely either an injector problem or improper engine loading. Engine loads are the most likely cause.

Your engines should turn up 2800 RPM @ WOT with a normal sustained cruise of 2400 rpm. If you can turn 2800 rpm with the throttles wide open, then you should have almost no transom soot.

If you can't turn 2800 rpm, too much pitch, a dirty bottom, or to much load on the boat are likely causes.

Start with the easy stuff first.......check WOT rpm's and then the bottom condition. In freshwater, slime or algae build up can substantially affect speeds and drag. Remember that Cat specifies sustained cruise as 2400 when the engines turn 2800 or 85%. So, if you are only getting 2600 rpm @WOT but you still run the boat @ 2400 rpm, then your load is 92+%. The engine cannot burn the extra fuel so you get soot.

If the bottom is pristine and you still cannot turn up 2800, then you should consider having some pitch or cup removed from the props.

Hope that helps...........
 
Frank,
Thanks very much. The bottom just may be the problem. Thanks for the info which is very helpful. Bought the boat a couple of years ago & don't know if the bottom has ever been done.
Steve
 
Owners of yachts powered by today's diesel engines now reap the benefits of running a finely tuned machine. But with that reliability, horsepower, and clean running come precise tolerances and computerized engine controls that need care and feeding—and expert service personnel when things go south.
Understanding why your diesel runs cleaner will help you to keep it that way. Many engines emit far fewer harmful gases in the engineroom now thanks to a system called the Walker AirSep Air/Oil Separator. If your engine has one, you need to keep it working right. And if your engine doesn't, you may want to look into adding one. Here's what you need to know.
After developing a similar device for the U.S. Navy in the 1980s, Walker Engineering introduced the AirSep Air/Oil Separator to the recreational marine market, and in 1989 it quickly became standard equipment on Detroit Diesel engines. In 1992, Caterpillar made them standard on certain models, including 3116, 3126, 3406, and 3412, as did Alaska Diesel. Cummins followed suit in 1994. And as the engines have evolved, the AirSep has changed with the times. They now have a more effective silencer feature, but the basic technology has remained the same.
 
I don't believe that is quite true.........

We've seen Air-Seps added to many 1994-1997 Caterpillar 3116 and 3126 powered Sea Rays by the dealer in our area. I think the addition of the Walker product was done by the company that marinized the base engine and was done per the requirement of the end user, in this case Sea Ray.

But, every diesel powered boat should have them........the boats are quieter and certainly run cleaner when the crankcase gasses are recirculated.
 
Eagle Attitude said:
I have a 1995 Sea Ray 440 Express Bridge with twin Cat 3116 diesel engines. It tends to blow black soot over the rear of the boat. I have been told to blow it out when I am out and sometimes that works and there is very little soot. I took a trip this weekend and blew it out good, but the soot was worse than ever. Anyone encountered this and have any suggestions for a fix?
Click to expand...
This may not help at all as the engines are different and I don't know if it is even required on the Cats.
When I bought our boat with the Hino diesels it put out black smoke so bad you couldn't see a boat behind us if we ran slow and then opened the throttle. The back of the boat was black.
Valve adjustment was a required mantance at 500 hours. The engines had about 1200 hours and it had not been done.
While at anchor I adjusted the valves and checked injector timing which required no adjustment.
Now I can run all day at trawler speeds and when I open the throttles there is a little smoke for about 15 seconds and then its clean. The only black I get on the boat is from the generator.
The only thing I did was adjust the valves and the smoke went away.
Hope this may be of some value.
Doug
 
dmcb: what this particular Cat has got is a Mechanical Unitized Injector, runs off a cam lobe, makes high pressure direct injection around 28,000 psi. Unfortunately it seats into a copper cup like on old Detroit. The injector itself actually looks very similar to the old 2 stroke Detroit injectors. Anyways the inj to cup joint seat likes to leak and aerates the fuel gallery within the head. This condition causes slow timing, black smoke, low power, ... A simple fuel pressure check usually picks this up. With regular overhead maintenance this engines fuel system is flawless.

Its also a turbocharged engine. So who knows what his boost pressure is. Might just have a blown boost hose on one engine.

Why these diesel boats have no fuel or boost pressure instrumentation I really don't understand.

The OP seems to be MIA here so:huh:.

Anyways. Welcome to CSR. ...Ron
 
BonBini said:
dmcb: what this particular Cat has got is a Mechanical Unitized Injector, runs off a cam lobe, makes high pressure direct injection around 28,000 psi. Unfortunately it seats into a copper cup like on old Detroit. The injector itself actually looks very similar to the old 2 stroke Detroit injectors. Anyways the inj to cup joint seat likes to leak and aerates the fuel gallery within the head. This condition causes slow timing, black smoke, low power, ... A simple fuel pressure check usually picks this up. With regular overhead maintenance this engines fuel system is flawless.

Its also a turbocharged engine. So who knows what his boost pressure is. Might just have a blown boost hose on one engine.

Why these diesel boats have no fuel or boost pressure instrumentation I really don't understand.

The OP seems to be MIA here so:huh:.

Anyways. Welcome to CSR. ...Ron
Click to expand...

Thanks for the welcome Ron. And thanks for the info on Cats. I know nothing about them and am glad to learn a bit.
Doug
 
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