Diesel heat exchanger and manifold repair

Barry Pickthall explains how he carried out engine repairs on a budget after a couple of years of Covid lockdown neglect

- Barry Pickthall

How many of us follow the full engine winterising schedule, especially if you keep your boat in the water? I'm probably one of many who have limited this to simply changing oil and filters and ignored flushing through the engine cooling system, especially when the engine intake skin fitting is difficult to get at. Well, we ignore these things at our peril!

More often than not we check that the water is flowing out through the exhaust, and eyeball the system for any tell-tale signs of obvious leaks, then let sleeping dogs lie, not realising that an unseen build-up of salts can seriously restrict the amount of water running through the heat exchange manifold.

I learned a hard lesson last spring after leaving my boat-and its inboard marine diesel-unused for two seasons because of Covid-19 restrictions. The saline water in the cooling system crystallized and gummed up the tube stack within the manifold, and because of the mix of an alloy manifold casing and bronze fittings, it also suffered electrolytic corrosion.

There were no outward signs of trouble, the problems were all hidden inside the manifold or at the back end of the engine - which in Sea Jay's installation is hard to see in the restricted engine space under the deck.

A cheaper option

The shock was all the more when I learned the cost of replacement parts-£279 for a part-exchange tube stack, and £439 for a new manifold casing. With fitting, it was going to cost around £1,000, simply for not following the full winterising programme-Gulp!