Sunday, January 10, 1999

Overheating Engine? -- Try Installing a Second Heat-Exchanger

One of the early problems we had to deal with on Momo was an over-heating engine.  Momo’s diesel is a Perkins 4108, which for all its virtues has frequently been faulted for having an inadequate heat exchanger.  Indeed, in cold water, our engine never over-heated at all.  It was in the warm waters of Mexico that we encountered the problem.  Later, when we sailed to the Pacific Northwest, the problem disappeared again.

Our solution was to put in a second heat exchanger.  We picked one up at a second-hand marine exchange--it's about twice the size of the original.  We circumvented the problem of mounting it on the engine by not mounting it on the engine at all.  Instead, we found a spot for it beside the engine and plumbed it between the engine and the raw water pump.  That is to say, the sea water actually passes through the heat exchanger before it reaches the raw water pump on the engine.  Meanwhile, the engine’s fresh water coolant passes through the original heat exchanger and then continues to the second heat exchanger.  We’ve never had an overheating problem since.

Used heat exchangers aren't that difficult to find, especially if you don't need to worry about getting a specific kind.  We paid less for our heat exchanger than for various bits of plumbing needed to hook it up.