The Exhaust Elbow
Everyone knows to check the exit of the cooling water from the exhaust when turning on the engine. It is standard practice to listen for the water to splash into the sea in order to make sure that the engine is being cooled. If not, you hear a very hollow sound and just brown/white smoke is coming out of the exhaust. The immidiate action should be to turn off the engine and find the fault, why no water is coming.
If water is exiting the boat via the exhaust it is assumed that it will continue to do so during the motoring period, but it is not forbidden to keep en ear on the water exiting during motoring as well. It might be difficult to hear due to waves splashing around, not to mention the engine noise. Luckily, engine noise is very low on a HR, but the center cockpit puts us into a position quite distant from the exhaust, so we can’t always hear it while motoring.
When no water is exiting the boat, we often assume that it must be the impeller. And it often is. To have a spare impeller goes without saying. An additional good safety issue is to upgrade the lid of the impeller housing to a SpeedSeal Life. This will prevent the impeller to break in first place, but if it does, it is very easy to check and replace the impeller very easily by hand (no screwdriver! no dropping screws under the engine!). The “Life” variety also has a teflon ring that allows the impeller to go dry for a significant number of minutes without destroying the impeller as such. Just don’t forget to service the SpeedSeal Life using their service kit every 600 engine hours. Boats should come delivered with a SpeedSeal as standard!
If it is not the impeller, it could be the fact that the raw water strainer is leaking air. Have you recently checked and cleaned the raw water strainer, not closing the lid properly? Air can then be sucked into the strainer and the impeller has difficulties to pump water and sucks air instead. The standard Volvo strainer (black and with a copper pipe inside that corrodes) should be replace by the transparent equivalent by Vetus with no corrosive parts inside and easily inspectable from the outside.
There could be another reason, however, why there is no cooling water exiting the boat. How about the exit? After some years and engine hours, especially in corrosive environment, such as sailing in a warm salty sea, the exhaust elbow on the engine corrodes from the inside. This is not visible from the outside. You will see shiny green looking at it, but it could be nasty from the inside! Inevitably it will look worse and worse over the years, finally blocking the entire exit like a heart attack. Before this happens, one should regularly dismantle the exhaust elbow and inspect it from the inside. By this, you also have the chance to check the turbo, especially if you dismantle the air filter on the opposite side. With a finger, you can check if it is turning freely or if it begins to cease due to carbon build-up. The carbon build-up is due to running the engine in too low revs, e.g. when using the Gori-propeller in overdrive over lengthy periods, but this is another issue…
See below photo of an elbow partly clogged preventing the water to flow freely. It didn’t need much and this engine did not get any cooling water at all any longer.