Perkins 4108 Black smoke under load

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DenisK

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I have twin 4108's, factory rebuilt in 1998, light use. Starts first time any weather, no knocking, fine at low revvs up to about 2400 but belches black smoke under load? The fuel is about 4 years old. Any suggestions/advice appreciated.
Denis, Hampshire
 
A few years ago I had a similar problem with a Perkins and various 'experts' gave their opinions and suggestions to the cause. Basically what had happened was due to a build up of dirt and grease in the air filter and a piece of clear plastic, similar to clingfilm, which had got caught in the air filter. This was starving the engine of the air it requires and with a quick clean everthing was OK.

May not be the solution to your problem but worth looking at.

David
 
G'day Denis,

Black smoke is a good indicator of too much fuel or not enough air flow.

Pop the air cleaner filter out and try again, if no black smoke clean or replace the air cleaner filter, also check for clear air ways, no kinks on hoses etc.

Avagoodweekend......
 
Thanks David, what you say makes sense. I am reasonably at home tinkering with an engine but for the life of me, I can't identify the air filter - at the risk of sounding like a doughnut, where is it located?
Denis
 
The air inlet on a 4108 is usually an upside down bowl shaped piece on the manifold. I dont think there is a filter as such on them, but cleaning out any muck wont hurt.

Are they blowing smoke on one or both of your engines?

If its only one, suspect a fouled prop or some kind of restriction to the air intake.

If its both engines, then its most likely that the props are simply too big, and try to push the boat faster overloads the engines and makes them blow black smoke.
This used to happen to my old boat with a bmc engine - 500rpm below maximum revs, it would start to turn the cooling water blackish, with visible black smoke at full bore. I never did change the prop, just never gave it move throttle than when it started smoking.

It could also be that the bottom of your boat is dirty and this is restricting performance.


Injectors rarely give any trouble unless your using poor filters and dirty fuel. I would leave them alone personally, and i suspect theres nothing wrong with them. The only time i serviced my injectors was when my engine were becomming increasingly difficult to start. The injector service improved that no end, but once it was running, you wouldnt know there was anything wrong with them.

In summary, i think your problem is most likely that you are simply over propped if your having the smoke with both engines, especially if the bottom of the boat is clean.

Hope this helps

Alex
 
I'm certain this is a load problem as`Alex has already said having been a victim of the same thing. My cause was a load of thin line around the prop. Not enough to stop it but enough to make it imposible for the engine to turn it at design speed.
 
I have the same problem, which is probably partly due to an over-long exhaust line.

But there was a survey of 4108 owners on the US CWBB forum a while back, and many reported that the maximum revs they achieved with this engine are surprisingly low, 2400 not being untypical. My yacht will be travelling at maximum hull speed at 2100 revs, beyond that the smoke (unburnt fuel) gets very black indeed. Otherwise the engine, now 30 years old, behaves very well indeed.
 
I had a black smoke exhaust problem with the Yanmar 27 on my Jeanneau.
It was not black smoke as I thought but unburnt fuel.
Engineers suggested that "overloading" of engine could be the problem.Remember those old deisel lorries going up hills in the the days before turbo.
Advice from three engineers..two in england and one in France ( where the boat was) Lift her out and check the prop.
There were enough crustaceans on the prop to make a "Fruit de mer platter).Scrpaed them off,polished prop now ok.
Get rid rid of your old fuel ,your probably barbequeing bacteria as well as blocking all the the filters whith the risk of fuel startvation when you might need it
 
lot of 4108s do seem to turn relatively slowly. My old norman would go to about 2800 maxmium, whereas a friends boat with twin 4108s would pull nearly 4000. My old BMC would also pull almost 4000 full bore.

i think the variations may be due to various power outputs that were available at different speeds. The marine ones being slower than ex vehicle engines.

I could be wrong, but I think the DPA injection pumps will have their maximum speed stamped onto them. My old BMC didnt but friends perkins did have. Its worth a look.
 
I thought it was just us that had a Perkins geared wrongly. We get 2100rmp then black smoke. But since we are definitely not under powered I have no complaints.

As for the air intake there are a few factors. The breather goes into the side of it with no drip back system so that the mist of oil in top of the engine just gets sucked straight into the filter.

The second problem is that cold start unit is like a bad candle sometimes and makes a lot of smoke.

Between the two, the gauze air filter just gets a bit sticky and blocked.
 
Thats interesting! My 4107 will do no more that 2400rpm after which the rev limiter kicks in and certainly sounds like the max it wants to do....However in the book it says 3500rpm..I dont think I would want to hear it do that...!


Air supply to the engine room/compartment could be a possible issue for the original poster..may be a vent has been blocked off

Nick
 
Try all of the above, but after that fuel even diesel does
de-generate after a time, and diesel is hygroscopic, (fancy word meaning it picks up every piece of dirt and junk around it).
so consider cleaning out your tanks, and changing your fuel.
Be careful where you by it, and if in doubt, pinch a pair of your wifes tights and use the knicker part as a filter,(thicker denier).
 
My 4108 is 28 years old it will rev to 3500 rpm, but no one in right mind would run it at that speed because, it does 6 knots at 1500 rpm, and the max hull speed is just over 7 knots, so 1800 is probably the best fast speed. any over is a waste of fuel and yes it does produce some black smoke at 3000+ rpm, but usually stops after a minute.
If the engine was recently rebuilt, then I would suggest looking at airfilters followed by injectors if they are clean.
If you want to see the manual ( for the location of the airfilter) try:-
http://users.firenet.uk.com/stewartbray/perkins4108.pdf
 
I had similar problems with my 4108. It was due to the engine running a bit hot, and thus overheating the poorly ventilated surrounding air. I suspected the hot air was thinner and thus starving the engine of oxygen at high revs.

It was fine once the heat exchanger was cleaned.

Philip
 
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