An Aussie guide to engine maintenance


To the editor: Years ago, on our circumnavigation aboard our 38-foot cutter Heretic, we had reached Cairns in northern Australia when we left the boat in a marina and returned to the U.S. to work during the Southern Hemisphere cyclone season. Our 3HM35 Yanmar engine — which we affectionately called Grunter — was raw-water cooled, so we worried about it corroding during its months of disuse. We ran fresh water through the cooling system until we thought it was thoroughly flushed.

In April, at the tail end of the rainy season, we returned to Cairns to find Heretic musty but unharmed — except for Grunter the Yanmar. He was all seized up. I couldn’t understand it; I thought we had flushed him out.

My husband, Seth, who is really our mechanic aboard, was less confused but therefore more despondent. “The problem is that I didn’t change the prop when we replaced the engine,” he enlightened me. The old propeller was pitched for a 50-hp engine and Grunter was only a 35. The big two-bladed prop had put too much load on our new Yanmar. Seth thought it had happened when we had first come into the Cairns marina seven months before. As we had pushed our way in against a strong headwind, we had both noticed an ominous black stain in the water astern. “The load probably damaged the head gasket and let water into the cylinders,” Seth concluded.

So we sat in the cockpit, mournfully staring down at the engine. Max, a local Aussie man, was walking toward us along the finger pier, barefoot. He stopped when he saw us. “What are you two so glum about?” he asked.

We told him about the engine and he offered to have a look. He gave the crankshaft pulley a jerk and said, “Yeah, it’s your pistons, mate. But it’s probably only a bit of corrosion. Just take the head off and give ‘em a whack.”

“Take the head off?” Seth looked skeptical.

“Why not? It’s only a couple of bolts. That’s what we did all the time on the farm. On the tractors.”

Heretic’s engine disassembled and the parts labeled.

Ellen Massey Leonard

Over the next few days, Seth disassembled Grunter, and I labeled each part and laid them on paper towels in the order in which they would have to return to the engine. Seth first removed the alternator and exhaust manifold. Then he unscrewed the fuel lines running from the injection pump to the fuel injection nozzles. As soon as the fuel lines came off, Seth covered them in plastic. He also covered the openings where the lines attach to the engine since even the smallest amount of dust entering the fuel system can damage the nozzles. Any jarring or bumping while removing or replacing the cylinder head can also damage the injection nozzles, so they were the next item on the list. Seth removed them and quickly wrapped them in plastic.

He then turned to the rocker arm cover, taking it off and handing it to me. One of the mounting bolts for the valve rocker arm came loose in the head as he removed the nuts holding the rocker arm. Seth handed me the valve rocker arm and looked at the bolt. Someone before us had adopted the do-it-yourself policy and had stripped the threads in the head. It appeared that the person had taken off the rocker arm and over-torqued the bolts when they had put it back together. Their solution, a Recoil thread insert, was poking up out of the head. Seth couldn’t drive it back in, so we would have to find a new one. “We haven’t seen Cairns till we’ve seen the Industrial Zone,” I joked. Heretic was built in 1968, so it sometimes felt that our circumnavigation was simply a tour of each nation’s machine shops and hardware stores.

Seth bent over the engine again. He pulled out the push rods that open and close the exhaust and intake valves, and I laid them on the paper towel. Then it was time for the cylinder head itself. He looked at the manual to see which bolt to loosen first. It is important not to have one side tight while the other is loose; the whole assembly has to come loose together. Seth started with the bolt numbered 11 in the manual and worked his way to the bolt labeled 1, loosening them in a crisscross pattern and turning his wrench less than an eighth of a turn at a time. When everything was loose, I helped him lift the head so that it would come off straight. We didn’t want to hit any of the bolts. Half of the old head gasket stuck to the cylinder head and half stuck to the engine as we removed the head.

I looked at the exposed pistons and saw a thin brown line on the wall of the third cylinder: the corrosion that was causing it all. Seth fished out a full bottle of Inox, Australia’s rather more persuasive version of WD-40, similar to PB Blaster, and emptied it onto the pistons. Max, the Aussie who had been the impetus for all this, had told us to drown the cylinders in Inox once we had taken the head off.

While the pistons and cylinders soaked, we scraped the old gasket off with plastic scrapers. Metal scrapers would have damaged the cylinder head and the engine block. Then Seth tried to free up the pistons by “giving ‘em a whack,” as Max had said, with a rubber mallet. The pistons didn’t move, but Inox splashed all over the nav station and our Great Barrier Reef chart.

“I’ll try something else,” Seth said and got out a scrap of oak to hold against the piston. He came down on the piece of wood with a large metal hammer. The piston still didn’t budge. He hammered at it steadily for an hour before handing it to me. My attempts were equally futile. Seth repossessed the hammer and piece of oak and thwacked at it for another hour and a half. He finally stopped, saying, “We’ll try again tomorrow.” But he looked defeated.

The engine block with its new head gasket. Note the covered fuel line openings at bottom left.

Ellen Massey Leonard

The next morning I set to work varnishing to the steady thunk of Seth hammering away below. It was almost noon, and I had finished the entire cabin trunk when I heard a triumphant “Woohoo!” from Seth. “It’s moving!”

“That’s so exciting!” I paused. “Now what?”

We ordered a new head gasket and when it arrived, Seth and I cleaned all the parts meticulously before coating the gasket with a substitute for ThreeBond 50, the sealant prescribed by the manual. Seth laid the gasket in place, and together we put the head back on, being careful once again to keep it straight. We lubricated the threads of the cylinder head bolts, and then Seth tightened the nuts in sequence with a torque wrench.

Seth managed to put the valve rocker arm back on without mishap, careful not to tighten the nuts beyond the correct torque.

He put the rocker arm back on before the six push rods because the rods would have pushed up on the rocker arm, making it impossible to mount it straight. To install the push rods, he turned the crankshaft pulley so that the rod he wanted to insert was at the bottom of its cycle; then he pushed down on the valve to lift the valve clearance adjusting screw and slide the rod underneath. Once all was in place, he measured and adjusted the valve head clearance with feeler gauges, moving each push rod to the bottom of its cycle to do so. The push rods are at the bottom of their cycles when their corresponding pistons are at the top of their cycles on the compression stroke. A mark on the flywheel indicates this correct position for adjusting the valve head clearance.

In order to see the flywheel, Seth had to remove the starter motor. He then replaced it, reconnected the fuel lines and injection nozzles, and reattached the exhaust manifold and alternator. It was nearing evening when he finally mounted the rocker arm cover. It had taken over a week, but Grunter was back to his normal appearance.

With hesitant anticipation, I went on deck to give Grunter a little throttle, and Seth turned the key. “He works!” I cried as I heard the comforting roar of a functioning engine. Seth just smiled and wiped his oily hands. Two days later, we puttered out of Cairns and soon we were diving among giant potato cod in Queensland’s coral-rich waters.

—Ellen Massey Leonard and her husband, Seth, completed a circumnavigation aboard their 38-foot cutter-rigged sloop, Heretic. They were recent recipients of the Cruising Club of America’s 2019 Young Voyager Award.

By Ocean Navigator