Monday Minute - A Damn Fine Measure of Engine Durability

Monday Minute lets me pass on tidbits from marine folks I have known over the years. Often a comment during a boat tour, or an off-handed remark as we walk through a facility, or a point made during a seminar, I find these words of wisdom in the pages of my PMM notebooks. While they are not usually meaty enough to fill an entire blog post or command an entire article, they are pearls of wisdom you will want to know.

 The legendary Gardner engine, the undisputed King of Marine Diesel Engines. This reconditioned Gardner 6LXCT diesel engine is ready for installation. I have been on boats that were built simply because the owners were able to locate a Gardner engine in running condition. 

The legendary Gardner engine, the undisputed King of Marine Diesel Engines. This reconditioned Gardner 6LXCT diesel engine is ready for installation. I have been on boats that were built simply because the owners were able to locate a Gardner engine in running condition. 

Before the introduction of electronic engine controls, every engine manufacturer provided a way to roughly measure running time before an engine could be expected to need major work done. An extensive engine overhaul replaces major parts that wear out, bringing a second or third life to an engine block in a boat. You typically find this in workboats and fishing boats where it is common to see 3,000 hours put on an engine in the course of a working year. Pleasure boats tend to be more along the lines of 200-250 hours a year, except in those boats that are underway much of the time, such as passagemakers and full-time cruisers. When Scott and Mary Flanders sold Egret after their extensive world travels, for example, their the boat's single Lugger diesel had over 14,000 hours on it and was still going strong.

So it is kind of funny when I hear a buyer thinking of replacing engines when he looks at a used trawler more than a few years old. The engines might have 2,500 hours on them, depending on the boat's age. In the back of his mind, he almost can't help including the cost of new engines in his offer. Even if the boat has had meticulous maintenance complete with full documentation, there is lingering concern that diesels in a boat that is 10+ years old must need to be replaced. What a waste of money! In the scheme of things, those operating hours are hardly enough to consider new engines unless there are serious issues.

Over the years we have seen trawlers powered by a variety of engines, and almost all of these engines can also be found in trucks and buses, farm and construction equipment, generators and pumps, and other applications besides powering boats. About the only difference between engines is often just what color paint the manufacturer uses to differentiate the various markets.

Anyway, it was common practice before electronic engine management for most engine reps to talk about engine hours as a good way to measure before an engine needs a major overhaul. Whatever that number was, and it certainly varied between engine companies and models, it formed only a basic measurement tool, and was no way an exact way to know what kind of hours that figure represented: running at full throttle, endless idling or very slow speed trolling, or long periods of non-stop operation vs many short start ups and short runs. Obviously, such wide variation of running time doesn't account for engine loads, or the stress on moving parts, and other factors that impact engine wear.

CAT 3208.jpg

In my experience, only one company, for one engine at least, held a different view of this concept. And it always struck me as a much better way to think of engine wear over the course of an engine's life. It was Caterpillar, and the engine was the hugely popular and reliable 3208. This eight-cylinder V-8 diesel can still be found around the world, powering boats and heavy trucks and construction equipment and everything else that requires heavy-duty diesel power. It was a very popular engine and only went away because Caterpillar could never hope to achieve stricter emissions standards with this engine design.

Rather than counting engine hours, Caterpillar spoke of engine life in terms of gallons of fuel burned, and in the case of the 3208 (and its three horsepower variations) that magic number was 30,000 gallons. When your engine consumes 30,000 gallons of diesel, the engine pretty much needs major work done, up to and including a complete overhaul.

CAT 3208 specs page 1.jpg

Just think how much sense that makes. If you spend countless hours idling or running at slow speed, you are burning very little fuel, especially in the naturally-aspirated, 210hp engine version found in many older Krogens and other trawlers. Higher horsepower variations, such as found in Fleming motoryachts and others, might be the mid-range 375hp turbocharged 3208 or the high performance 435hp engines. Such higher horsepower engines burn fuel at a much higher rate, and it just makes sense that those engines would reach a point of needing work done sooner than a low-stressed diesel running along under load but not being asked to work hard.

When you look at fuel burn curves for the various 3208 engine packages, it is easy to see how the gallons per hour consumption is a great identifier of what the engine is doing and in what operating mode. The 210hp 3208 in a Krogen 48 Whaleback, loafing along at 6 knots approaching Ketchikan, is burning a whole lot less fuel (and working less) than a motoryacht with both engines lit up on a plane at 18 knots. The motoryacht owner will reach that magic 30,000 gallons a lot quicker on those 435hp Cats if he or she keeps that up!

Of course, today's modern engine technology takes a lot of this "ballpark" estimation out of engine ownership, and it won't be too long before your engine makes its own appointment with your local service shop for routine maintenance. But for owners of older boats, and those considering vintage trawlers with engines that don't have such capabilities, I always thought the Caterpillar approach with the venerable 3208 made a lot of sense.

Have a great week.