exaust smoke

[Carlhere]

Hi everyone,
Hopefully someone can help me nail this problem with exaust smoke on the port and starboarb sides of my boat
I have a 1985 Trojan 11 meter international model equiped with twin detroit 671 engines.
This boat has the exaust ports on the sides of the boat. There is about 7 holes just below the water line where the exaust comes out. About 2 feet forward of that there are clam shells on both sides above the water line. Inside those shells is a flapper that from what i've learned should be closed and exaust should not come out of this area but do not cutoff any exaust totally and completely. Some blowby will get through.The flappers I have replaced recently. The problem is from these clam shells I get a black smoke line on both sides of my boat which is un-bareable to deal with and makes a mess of the sides of the boat. Not easy to clean either. A horable site to see. Infact I hate to use the boat due to the massave cleaning afterwards for a short ride.
Please note the trace of smoke is not from the 7 hole exaust ports but from the clam shells only.
Can anyone shed any light on this?? Anything I can try to eliminate this problem? Or reduce it? I would appreciate any advice.
Thanks Carl

[prowlersfish]

Soot if not fun to deal with , first are the engines able to turn up full rpm under load ? and at what speeds are you having this issue at ? .


On a side note what is your top speed ? ( trying to find real world numbers to compare )

[Carlhere]

Yes these engines can achieve full rpm. I normally run about 1700 to 1800 rpm. It seems I get this soot problem no matter what rpm I'm running. Any ride I go for short or long....when I return the sides of the boat are black from the clam shell all the way to the stern. Even the cockpit gets some blackness in it.
The top speed can achieve about 24knts

[prowlersfish]

Ok can get full rpm under load ? 2500 ? and you normaly cruse at 1700 -1800 , what speeds are you getting ?

What I am working at is a possible over loading condition causing black smoke .

[Carlhere]

Pretty much at 1800 rpm I am at about 18knots.
1700 rpm 17knots.
I have noticed the rpm pretty much matches the speed in knots only varying slightly depending on water condition. Wind and tide movement after being planed up.
Also please note im getting this black smoke soot from the clam shells no matter how many people are on board. It doesn't matter if it is 2 people or 8 people. It makes no difference

[RWS]

The answer Paul is looking for is:

What is your top, sustained, full throttle, maximum RPM in the water and under a load.

Also known as WOT - Wide Open Throttle.

This number will expose a possible OVERPROPPING condition, which would create the black smoke.

As far as those vents are concerned, my guess is that they are simply a vacuum break.

When I upgraded to diesels, John Leed at Marine Tech in Lancaster suggested that I add them and he supplied the required exhaust elbows with the correct nipples in place.

RWS

[Carlhere]

Hi Paul
Sorry for the misunderstanding.

I can achieve top rpm of 2500. Both tachometers are even for both engines. The top speed is 25 to 26 knots depending on conditions.

Carl

[mikeandanne]

black smoke is unburnt fuel for one reason or another------ one thing you can do yourself is to make sure your intake airs are clear and unrestricted,clean filters etc-----are both engines the same and how many hours,have they been the same since you have owned the boat or is this recent ?---- Mike

[Carlhere]

Hi Mike,
I have this 1985 Trojan for 2yrs now. These engines are the same and have 1050hrs on them. They had a smoke soot line on the sides from the day I brought this boat home 2 years ago. That was about a 9 hour ride. Boat engines run very well and strong.
Recently the aft cooler and heat exchanger was done on the starboard engine. To include the turbo charger. This was done because it was leaking oil on the exaust side of the fan. However this did not reduce the smoke soot situation coming from the clam shell. Where the water and exaust exits the 7 holes on the sides of the boat it never has any smoke or soot arout them. It is only coming from the clam shell. In this very moment the same is being done with the aft cooler and heat echanger on the port engine.
Air canister is clear on both engines and recently replaced the sock around both of them. These canisters are original and it seems the only thing filering the air is the outer sock that wraps around them from the outside. I've been considering replacing these with Airseps!
Oil was changed just recently with only 10 hrs on engines since the change.
Diesel fuel filters units are the original (DAHL) units. The filters inside were changed when the oil change was done. Also I've been considering replacing these with Racor filters.
The fuel i'm using is the red diesel purchased at the marina and is not always from the same marina but always using red diesel purchased on the water. It is not the clear or yellow diesel for on road vehicles.
The engines do have a throttle sync which I use when planed up. When used the tachometers are running even and I have confirmed this on the tachs from the upper and lower stations.
I have a friend in the same marina that has the same exact boat and same engines. And the hours of use are close to mine. Boats are identical in every sense. He does not have this smoke issue from the clam shells on his boat.
He has still the original air breather canisters with a recently replaced sock on the outside. He does however, have the racor filters for both his engines. He does not recall if before replacing and upgrading to racor filters if he had a smoke problem from the clam shells on his boat.
I would really hate to start replacing everything and not nail this problem and learn it is still something else.
Even still, my plan is to go with airseps and racor filters for my boat because I know it will serve my engines better. I'm still sceptical though, if this will take care of the issue. I have a feeling it is something else?
Carl

[RWS]

Believe it or not, today you can get a decent phototach for less than $20.

I did.

http://www.amazon.com/dp/B001N4QY66/ref ... 25410_item

This little tool showed that my engines were turning 200RPM less than the tachs showed.

After some WOT runs with full fuel/water/waste to collect data, I will be sending my props out for propscan tuning.

I strongly suggest spending $20 and verifying your tachs before going any further.

RWS

[Carlhere]

RWS,

Thanks for that link for the Tach from amazon. I have ordered that tach and will give this a shot. I have known that if the engines were out of sync that you can be dealing with a smoke issue. Even though my boat tachs are showing they are running even I will try this tachometer while running to see if something is off as well as with the engine syncronizer.
Hopefully others will see this thread and join in with some futher input and ideas. Any maybe someone with the same boat that has dealt with this issue and has found the solution to correct theres. Because truthfully, when the day comes that this problem is nailed, and when the smoke clears!! I will enjoy boating a whole lot more!!
Carl