Why has our cruiser’s exhaust taken up vaping?
Our Volvo diesel’s wet exhaust system puts out a lot of white smoke (or water vapour), more as the engine load goes up, and I have a feeling the cooling water blown out is less than it used to be. Is this indicating a problem?
TONY REPLIES: My first thoughts are lack of raw water being injected into the exhaust, which agrees with your observations, and the white fumes are water vapour. When wet exhaust engines suffer a lack of exhaust water it also compromises the engine cooling, but you do not mention hot running or overheating. Assuming you keep your raw water inlet and weed strainer/mud box clear of debris, the raw water pump’s rubber impeller has probably failed.
It has a number of flexible rubber wings which eventually fall off, often passing into the cooling pipes and jamming in a bend or elbow, blocking water flow. Also, some of these pumps run without proper bearings so the shaft or body can wear reducing the efficiency. The pump, pipes and hoses are the first things to check including making sure all the joints between the raw water inlet and the pump itself are absolutely airtight.
If the pump is in good order you might have a partially blocked exhaust, causing back pressure in the raw water system to prevent the pump from moving enough water. First make sure the exhaust-raw water mixing elbow is free of scale. Then carefully inspect the exhaust hose in case it is suffering internal delamination, which can hang down in the exhaust stream and be pushed further down as the exhaust flow increases, blocking the exhaust and producing more back pressure (and often an audible hiss).
Too much or too little?