March 13 , 2008 - Engine Longevity
by Michel & Jane DeRidder

We've just overhauled our 37-year-old Isuzu diesel engine. What are the secrets that led to the engine's long life?

When Michel planned the engine installation, he thought back to his early days in Vancouver when he was involved in converting a fishing boat to make a collecting vessel for an aquarium. After this long-ago project, and several subsequent restorations, he realized that most engines died from salt water corrosion. He decided we must have fresh water cooling, and also a totally sealed and dry engine compartment. He made a water catchment around the propeller shaft gland, and he sealed the cockpit floor with a bead of flexible mastic, in those days with Thiokol (a marvelous product - so much so it was used on various space shuttles many years later). Nowadays he chooses to use Sikaflex. To make sure the seal can be removed more easily than by cutting it free with a knife, he first inserted a string into the joint all the way round to be tugged at to open the seal when the time comes.

Michel sealing the cockpit floor.

The DA220D Isuzu is a sturdy industrial engine built to last, and built to be rebuilt when necessary. It is fitted with a decompression lever so that it can be revved up with the starter until oil circulates before firing up. This 75hp Isuzu, replacing the original 35hp Isuzu, is a far larger engine than we need for best economy power, but with our variable pitch propeller we can run it efficiently at 1000 to 1200 rpm, just forty percent of what it can do. At such low power output, the moving parts are running under light loads and sustain little wear. We seldom run it just to charge batteries, so we do not often run it without a load. (Our power needs are comparatively modest, even today, with the limited number of electronic gizmos we own.) Diesel engines need a sufficient load to bring the combustion temperature high enough to burn all the fuel and leave little carbon deposits.

Rebuilt Isuzu engine, back where it belongs.

Before leaving the boat for several weeks or months, as we occasionally do, we have never asked anyone to come in to run the engine for us. Instead, just before we leave, when the engine is cold, we give it a very short burst of just a few seconds to distribute oil throughout, long enough to coat its entrails and stay put, but not long enough to heat the oil up. (Hot oil runs out, leaving bare dry metal for the next start.)

Lastly, realizing that it is cold starts that wear an engine most, Michel rigged a pre-lube system so that before starting the engine we shoot oil into the oil feed passages of the engine - bearings mainly. What we have on our engine is a 2" pipe cylinder nearly 3 feet long with caps top and bottom that is used as an oil storage under air pressure. The bottom of the cylinder is connected to the engine oil pressure line with a shut-off valve. The top of the cylinder is fitted with a car tire valve, to evacuate any over-accumulation of oil, two or three times a year. What we do is open the valve before we shut off the engine to let oil accumulate in the cylinder against an air cushion. We then shut off the valve before stopping the engine. Later, before restarting the engine, we can let that oil pre-lubricate the engine by opening the valve before we start the engine. With oil in it, a few revolutions with the starter while decompressed, and the oil pressure comes up before actually firing up. We keep the oil accumulator valve shut until we stop the engine. This simple thing seems to have helped our engine endure. After 17,000 hours the crankshaft is immaculately polished and shows only fractional wear.

Photo of pre-lube pressurized oil chamber

Photo of oil valve

The last time we removed the engine out of Magic Dragon was in 1984, half a world away, when Michel had to replace a bent con-rod due to a faulty injector leaking fuel into the cylinder while the engine was not running. We had left the electric fuel transfer pump turned on and it created enough fuel pressure to let fuel into the number one cylinder. On starting, enough fuel was in the cylinder to hydraulic and bend the rod slightly even though the exhaust valves were open on decompression. At that time we took the steel fuel tanks on either side of the engine out so we could inspect and repaint them.

We are delighted that we decided to revitalize this engine, and that Michel is still able to do so. It is satisfying to know that we can again rely on the old engine without having to worry about how much longer our luck can last.

How wonderful it would be to be able to find the skill and wherewithal to rebuild our own carcasses when the need arises!

Photo of us in the dinghy taken December 2007. ThereÕs life in the old dogs yet!