Subject: Smoking Volvo

I have a 200 hp Volvo Penta Duoprop on a 26 ft planing hull weighing 3.2 tons laden. According to the experts I should achieve a top speed of 28 kts at 3800 rpm, and cruise at 20knts at 3000 to 3200 rpm.

My problem is that my engine takes about 1.5 minutes to start from cold and emits huge amounts of white smoke which reduces somewhat after warm up. When under way it will not rev any higher then 3000 rpm and mostly often than not will only reach 12 to 14 kts. It emits black smoke under these conditions. If I continue to give more throttle the temperature gauge starts rising well above 90.

I live in Ireland and my boat is located 200 miles away from home so I can only travel at weekends. I have had the injector nozzles done 4 weeks ago and very little difference in performance. All filters have been changed within the last 3 weeks. I have noticed that the air filter is now very black and oily in a very short period.

Some of my pals who are self appointed experts tell me that the timing is out or the turbo is dodgy, I have looked into the turbo and the blades are clean and there is no play on the shaft so I am assuming that it may be okay. I may also add that it is using a lot of diesel but this may be caused by it not getting up on the plane properly. I would appreciate any help, information and advice you may be able to provide.

Regards James H

Dear Mr H

I regret that my main expertise is in inland craft so 200hp with patent prop systems is rather outside that, but I make a few comments that might or might not help.

1. Has the boat ever reached the speeds the "experts" say it should? If not, perhaps they are wrong.

2. When was the hull last scrubbed - a fouled hull can stop the boat climbing onto the plane and yours is clearly not doing that.

3. Is 200hp (assuming the engine is developing that power and the prop/transmission/engine/hull are all correctly matched) enough to get it onto the plane?

How long has this white smoke been going on? Most diesels have a tendency to emit white vaporised, but unburnt, fuel when first started, some more than others. The longer the engine spins over for before firing, the more it is likely to do it. On a boat like yours this should disappear within minutes of putting some real power on. The fact that it only reduces suggests a problem and I would normally first go for injectors, but as you say you have done yours I fear it may be something more fundamental.

First - if you have glow plugs for starting (I doubt that you do) make sure they are all working - removal and a physical test across a battery is often the easiest way.

Second check that the exhaust hose is completely clear along its length and not delaminating internally. Next remove the exhaust mixing elbow and check that is (and the exhaust manifold as far as you can) not partially blocked with soot/scale/salt/corrosion.

If all that is ok it must be worth a test run without the air cleaner element.

Once you have done this lot you are left with the conclusion that there is either an injector pump fault (could be timing or bad internal adjustment) or an internal; engine fault - lack of compression, dire need of decoke, head gasket etc.

Now the oily air cleaner.

All engines have some sort of ducting from the chamber above the crankshaft or the rocker/cam cover into the inlet manifold these days, it is called a crank case breather and lets the pressure that leaks past the pistons escape before it builds up enough pressure to blow oil out of the engine joints and seals.. In many cases, on this is a hose running into the air cleaner box, so inspect your box and if the oil is more concentrated around a hose inlet (usually about 12 to 18mm od) you can be fairly sure that too much pressure is leaking past your pistons indicating a worn engine.

I note that this would tie in with a reluctance to start and the production of white smoke as described. Only you know how many hours the engine has run for, how well it has been looked after etc, so only you can judge how likely this would be.

I can not see how a faulty turbo would oil up the air cleaner without causing clouds of blue smoke because if the oil seals had failed the turbo would blow oil into the cylinder, not back towards the air cleaner. Pressure pulses as the valves operate may be able to blow some oil back, but without blue smoke I would suggest that the turbo is probably OK.

It would be worth checking your turbo boost pressure if you have a waste gate or dump valve fitted (usually a waste gate, but some diesels have neither) in case it is leaking or maladjusted and so you do not get your correct boost - this could lead to black smoke in the speed that the turbo operates in because of lack of oxygen to burn the fuel, however in your case I rather doubt this is the case, but its worth checking..

Now the black smoke.

When a diesel has its speed held down below its maximum it is likely to make black smoke. This is called overloading, and it is one way a displacement craft (not yours) can check to see how well its prop is matched to the boat. If the engine is down on power so it is no longer capable of putting the hull on the plane or if the hull is dirty so the engine is not powerful enough to push it onto the plane the boat will try to operate as a displacement hull. The hull assumes a bow up attitude as the stern falls into the trough of the bow wave and your engine is trying to push the whole boat uphill, wasting power in excess wave making. I suspect that if you simple eased off the throttle until the trough of the bow wave was part way along the hull the smoke would go, but you would only be doing about 5 or 6 knots. The rising coolant temperature does not surprise me under these conditions, I would have liked the cooling system to have been designed to cope with them, but cost is all these days.

I think you should ignore the "overheating" until you have solved the white smoke problem and can get the boat on the plane.

I fear this has not been much help and also fear that it indicates a rather expensive time at the hands of the "professionals"

Tony Brooks