Aging marine engines.

Our boat is already 20 years old. It has Volvo MD2030 engines, and in the last years I have been reading more and more posts about older Volvo engines and problems that seem to originate from corrosion. Coolant disappearing, rusty coolant, leaks. 

The MD2030 and many other marine engines has a freshwater and a saltwater cooling system. They are supposed to be separated. But with wear and corrosion there are possibilities that the saltwater can enter the freshwater system. The freshwater coolant can also find disastrous ways as a result of corrosion. The latter happened to us this summer.

We found ourselves in a small island harbour with hydraulic lock in the port engine. Could not be turned. Water in the cylinders was the first thought, and it was correct. All 3 were full of coolant. But where did it come from? The heat exchanger housing had been off a couple of years ago, looked OK, so a cracked engine top was suspected. After dismounting it nothing wrong was found. Luckily, via some social network groups I was steered to inspect the heat exchanger housing thoroughly. A tiny hole was found in the exhaust area. Probing it, the edges fell apart, and the hole was suddenly big. Corrosion had eaten the area. 

We had to buy a new heat exchanger housing. They are quite expensive. Trying to find a welder could have been an alternative, but success was uncertain, and so was the time spent in the process. 

After returning home at the end of our sailing season, I cleaned up the exhaust area. The hole got even bigger. 

But still I had a hope of making a repair. The starboard engine has gotten rust in the coolant during summer, and I fear something the same can happen to it. I believe I need to replace that heat exchanger housing too. So I brought the old port one to a nearby welder. He was a bit sceptical because he thought the housing is cast aluminum and difficult to weld. Anyhow he managed to weld it. It was like welding in bisquit material he said, and there is of course no knowing how long it will last. The area was painted with epoxy primer, I do not know if it will have any anti-corrosion effect. 

The plan is to mount the welded heat exchanger housing on the starboard engine. Then I can see if the new coolant will not become rusty. And check on the other housing, maybe have it welded if there is a small hole in it. I paid the equivalent of £1000 for the new part, so a good repair of an old one is tempting.