Once, I Knew One Thing: An ExhaustNotes Review

When I first started working on boats there were only two choices if you wanted a generator: Onan or Kohler. This was in the 1970s. Most all the equipment on boats was still made in the USA and China was largely an agrarian society with little industrial capacity. It seems impossible with today’s global economy and seemingly unlimited options but we got along fine with just the two manufacturers.

Onan generators were the most popular in the territory I covered which was from Balboa Island up near Los Angeles to San Diego. The company I worked for, Admiralty Marine, was on Shelter Island right off of Rosecrans Street. Admiralty Marine sold a lot of Onan generators. One year, Woody Peebles and I installed 51 new generators. That’s only one a week but you have to realize we also did engine installations, ElectroGuard corrosion control systems and repaired and serviced all those Onan generators.

To install a generator isn’t as easy as it sounds. You don’t just plop it on the deck and plug it in. The California boats were pleasure yachts and everything was varnished if it wasn’t polished or oiled. You had to cover all surfaces with cardboard and plywood before starting any work. Making things worse, the generator was usually buried in the engine room behind the main engines, batteries and a zillion other components down in the bilge.

To get the generator out might mean removing the rug, lifting heavy hatches, taking off exhaust manifolds on the mains or moving water tanks and cross beams. Then you had to brace underneath the deck to support the portable A-frame hoist used to lift the generator out of the hole.

The portable hoist was portable in name only. The thing weighed a ton. Consisting of two steel uprights, a steel crossbar, a chain-fall and a metal box full of wedges, lifting eyes and the carriage that slid on the crossbar. All in, the hoist weighed about 300 pounds. We didn’t trust aluminum. You had to carry each piece of the hoist down the dock and onto the boat without causing any damage. Except that anything the hoist touched was damaged.

There were no store-bought portable hoists; you had to make them yourself or pay someone to build a hoist for you. I made my own and still have it baking in the sun here at The Ranch in New Mexico. You never know when you’ll need to pull a boat engine 500 miles from the closest ocean. Working with the hoist all those years I became attached to the thing. We’ve been through a lot of wars, you know? So much heavy lifting, I can’t bring myself toss it out.

It took about three days for me and Woody to remove an old generator, clean up the mess and install a new generator, roughly 24 hours labor times two men. At my hourly rate I made 78 dollars for the job. Admiralty Marine charged my labor at 600 dollars for the install, clearing 522 dollars once you deduct my pay. I never knew what Woody was paid. Probably more than me as he was the brains of the operation. The cost breakdown on these jobs was a great lesson in capitalism for me.

On rare occasions we worked on gas-powered generators but they were usually old wooden boats with cash-strapped owners. The Onan generators we worked on were almost all diesel-powered. The block was modular: 1 cylinder for the 3000-watt, 2 cylinders for the 7500-watt and 4-cylinders for the 12,000-watt version. The 4-cylinder used two, two-cylinder heads.

The early models used a CT (current transformer) set up to control the field voltage, which controlled the voltage output. In a nutshell, the power output leads went through these big CT’s on the end of the generator causing an inductive current in the CT’s and the CT’s sent power to the field. It was self-regulating, always varying the field current to suit the load. I never fully understood CT generators but luckily they were fairly reliable. Newer, solid-state voltage regulators superseded the CT voltage regulators.

The new solid-state Onan generators were a mechanic’s best friend. They broke down at such a regular pace you could forecast your income years in advance. The start-stop-preheat circuits were analog. It looked kind of funny: the top of the control box where the voltage regulator lived was all space-age but underneath that were stone-age relays, big brown resistors and purple smoke.

None of the Onans had counter balancers so they shook violently when in operation. The single-cylinder was the worst; it had soft rubber mounts that insulated the boat from vibrations. Fortunately for us repairmen the relays and wiring was susceptible to vibrations and would shake to pieces. Parts were always breaking off the things.

One time I installed a single-cylinder Onan in a boat and a week later the owner called saying it had stopped running. I went to his boat and found the flange that the seawater pump bolted to had fractured. Without sea water to cool the heat exchanger the engine overheated and shut off. The flange was steel and it was sandwiched between the timing cover and the block so you had to dismantle the front of the engine to replace it. It was such a crappy design.

The “One Thing I Knew” was the control circuits for the Onan. I understood them better than the other guys at the shop and could trouble shoot a problem in no time flat. I didn’t fall into this easy knowledge; it took a few years of trial and error before I could visualize the flow of electrons on their path through the various old-fashioned relays and resistors. All the wiring was the same color. Onan printed numbers on the wires to help identify which was which. These numbers were not always intact or positioned in a way that you could see them.

We rebuilt the engines and the fuel systems as the twins and 4-cylinders had a habit of breaking crankshafts. The twin had two main bearings, the four had three mains. The cranks would often break where the alternator rotor connected. They would break in such a way that the generator would keep running until it was shut down, then the crank would bind and the owner would call us saying “I don’t understand it, the thing was running fine when I shut it off. Now it’s stuck” After a few years of rebuilding engines we discovered that Onan sold a new long block for about the same price as we could rebuild an engine. It even came with a warranty. That made turn around much faster.

The governor (that controlled the engine RPM, thus the frequency) was a ball and cup type of deal driven off the camshaft. Centrifugal force would move the balls outward pushing a cup away from the cam. The cup was connected to an arm that controlled the fuel control on the injector pump. With the balls at rest the fuel was set for full throttle. As the balls slung out it reduced fuel. This seesaw effect could be fine tuned by adjusting a governor spring. Both tension and leverage were set by the hapless mechanic moving one thing affected the other.

After a few thousand hours of steady state running the governor balls would wear a groove in the backing plate of the cam gear and no amount of tinkering could get the frequency steady. Pulling the cam gear was the only way to get the thing to run without hunting. I liked to tell the owners that they were lucky the thing ran long enough to wear out the governor.

All those things I knew are just trivia now but they seem as real as this computer I’m typing on. The old Onan generators are long gone, replaced by modern diesel engines made overseas. Nothing breaks off the new stuff. My brain is full of things no longer useful, information that has no application in today’s world. I wonder about the knowledge the old ones that came before me took to their graves and if someone in the far off future will wonder about mine.

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