Beta marine - raw water air pocket

[nanubhana]

So recently my boat has been hauled out and place on the hard. I did all the necessary with regards to winterising, however on this occasion some water/antifreez mix does not fill the whole system. So between the seacock and impeller there is air. Will the air-pocket work it's way around once the engine starts? Any advice would be useful.

Thanks.

[tkeithlu]

Your water pump">raw water pump is a "displacement pump," meaning the impeller grabs a chunk of water or air and sends it forward, unlike a centrifugal pump, which simply pushes the liquid or gas. Therefore, your impeller pump is self priming, and can suck an air pocket through. It will throw that pocket out when you start the engine. But, your pump may leak backwards, such that compressable air will not prime, or the pocket could be too big, such that the impeller will heat up from friction against the walls of the pump and melt. That can really spoil your day and let your engine overheat as well.

So, whenever you start your engine, not just this time, look over the side and see that cooling water is being discharged. After a few minutes, check that the discharged water is warm/hot as well; that means that it is cooling the engine.