PS Advisor November 15, 2000 Issue

PS Advisor 11/15

How Long Do Diesels Last?
We took our boat out of the Freedom Yacht Charters fleet service in the British Virgin Islands and had it transported to California. As part of the preparation for the cross-country transport, I had the engine serviced and thoroughly inspected. The engine time was 2,250 hours. I tried to get some information from Yanmar about the longevity of their engines and about whether major overhauls should be done and at what intervals. I was left with the impression that there are too many variables for the manufacturer to advise anything specific.

In your June issue, Nick Nicholson said he had to have an engine overhaul at “almost 2,000 hours,” far less than the 10,000 hours that Yanmar vaguely quoted.

Is there a consensus as to how long a marine diesel should last? Should a major overhaul be based solely on engine hours? Is there any data from manufacturers about average engine longevity, if the recommendations in the manual are meticulously followed? Because charter service may represent some of the harshest engine use, perhaps the major charter fleets can provide some insight.

Stephen K. Lemon
Santa Barbara, California

In Nick’s case, the real problem was that his Perkins engine was ordered with the bare hull and it sat for 10 years. All the seals dried out and leaked, despite his turning the engine periodically.

A marine diesel, properly maintained, should go about 10,000 to 15,000 hours. With average maintenance, it should last 8,000 to 10,000 hours. Even poorly maintained, it should last 4,000 to 5,000 hours.

A Westerbeke spokesman told us that an oil survey crew bought a new engine, ran it harshly under miserable conditions and never did anything but add oil…but they got 3,000 hours out of it. He said it was badly worn.

He also said—and you’re going to love this, Mr. Lemon—that charter boat operators generally take excellent care of diesel engines. Consequently, the engines usually last longer in the charter business than in private usage, where an engine may be used intermittently, without scheduled maintenance.

Automobiles often go 150,000 or 200,000 miles on a diesel engine, without any service other than oil and filter changes. Ask any Mercedes or Peugeot owner. Averaging 40 mph, that would be about 2,500 to 3,750 hours. A diesel in a car probably gets worked harder than in a boat, mostly because of variances in temperatures and speeds, and many more starts and stops.

On the other hand, a boat diesel carries a heavier constant load. It must move water continually (it likes the load), whereas a car, once speed is built up, has only to overcome air resistance to maintain speed.

The diesel’s forte is heavy work, continuous operations (but it doesn’t mind varying speeds). With too-light loads, it tends to soot up.

What a diesel likes best is clean oil, clean fuel and a cooling system that keeps it at a constant temperature.

Backing Plates
I am always reading about the importance of backing plates when installing deck hardware, but I’m not sure what they are. Please explain.

Adrian Peters
Lac La Biche, Saskatchewan

Say you’re installing a cleat with four bolts. Loads on these will not be even. The pull of a dock line might try to lift the farthest bolts while driving the closer bolts down. Individual washers cannot equalize or distribute the load among the four bolts as well as a single-piece backing plate made of, say, 1/4" metal or 3/8" fiberglass, which reduces the risk of cracking the surrounding fiberglass deck.

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