This poor customer has a issue with his 108 Perkins in his boat . His email below

I have a question about my own boat. I am currently in the Philippines and have been having problems for a good week or two, If you could take a minute to help me trouble shoot it would be really appreciated…

Engine is 50 hp Perkins 4108. Was overhauled by local mechanic last year (2014) bench test post rebuild was all good (not under load). Sent injection pump and injectors for overhaul/service and once returned engine ran terribly- much black smoke and thick black exhaust ‘gunge’ (black and carbon like).


Symptoms are

In neutral (no load) engine will move through rev range up to approx 3200 rpm as expected ~ clear exhaust with only a bit of black when very close to WOT (upwards of approx 2800rpm)

Once gear is engaged (fwd or reverse) engine will operate normally at idle speed (approx 700 rpm) then accelerate typically (clear exhaust and prop/boat speed) up until approx 1100 rpm after which much black smoke is noticeable and black ‘gunge/carbon’ is in the exhaust and floating on the water (appears to me be improperly combusted diesel).

There is still throttle left but as you accelerate further there is no increase in prop speed/boat speed or rpm increase, just more black smoke/’gunge’.


What we have done

  • I have adjusted the timing of the fuel pump and the engine as per instructions of Perkins manual; I have managed to increase the RPM max to a little over 1700rpm before black smoking symptoms begin which is encouraging coming up from 1100 but still a little way off.
  • I have also managed to set the engine to 18 degrees before TDC and double check that the fuel pump is timed for correct injection point.
  • I have run tests tied to the dock and out on sea trial with no change to the symptoms.
  • I have checked throttle morse (removed and accelerated manually).
  • I have checked the stop morse (removed to ensure it was all the way in the open position).
  • I have removed the air filter (engine is naturally aspirated i.e. no turbo) and checked airway is clear.
  • I have removed and inspected exhaust manifold, elbow and water trap/muffler box. All were completely clean.
  • I have even disconnected exhaust pipe inside engine room and filled the boat with smoke to ensure no blockage further along…
  • I have checked and changed all fuel filters. some a couple of times.
  • I have inspected all fuel lines and replaced any suspect.
  • I have run with fuel line assisted by electric pump to aid if lift pump was having difficulties. (also with a temporary ‘day-tank’ (Jerry can) set up higher than the engine.
  • I have removed and replaced all injectors.
  • Changing timing on inj pumps has had some effect on rpm range under load but always still end up with black exhaust at some stage.
  • I have checked and rechecked valve clearance.
  • I have removed timing cover and checked that the timing marks are correct, and that no 1 piston is in TDC firing at the correct time. v/v timing is correct as are v/v clearance.



So what do you think is the cause of this mans problem ? In my next blog i will tell you my thoughts and what the outcome is.


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