Ford Lehman 120 and 135: what to check on a classic trawler diesel

The Ford Lehman is the engine behind a whole generation of trawlers. The 120 is based on Ford's 2715E industrial six-cylinder diesel, marinized with a different circulating pump and other parts.¹ The 135-hp version powered boats like the original Krogen 42.² You'll find Lehmans in Grand Banks, Krogens, Taiwan trawlers and many more boats from the 1970s and '80s.

A healthy Lehman is slow, steady and easy to understand. It isn't obsolete; it's simple. Just make sure it's been looked after, because a tired one can cost as much to rebuild as a modern engine costs to buy.

Ford Lehman at a glance

Is a Lehman-powered boat right for you?

A good fit if you want a simple, mechanical diesel that a handy owner can maintain, you're comfortable getting parts from specialists, and the engine has records and a good oil analysis.

Think twice if you want modern smoothness and economy, the engine has a history of overheating, or no one nearby has worked on one.

What to check

The cooling system

Heat exchanger, raw-water pump, hoses and the exhaust manifold. Owners discuss replacing original manifolds with stainless versions.¹ Ask when the heat exchanger was last cleaned and the raw-water impeller last changed, and look for coolant crust around hoses and fittings.

Oil leaks

Some weeping is common on old engines; heavy leaks aren't. Look under the engine and transmission with a flashlight, and look at the bilge below. Ask the surveyor what's normal for that engine.

Cold start and smoke

Arrive to a cold engine. It should start cleanly. A puff of smoke on a cold diesel start is normal; persistent blue smoke suggests burning oil, and white smoke that doesn't clear when warm can mean coolant getting where it shouldn't.

Oil analysis

Send an oil sample to a lab for wear metals, fuel and coolant. One popular lab has charged around $35 a sample,³ and it's one of the cheapest insights you can buy on an old diesel.

Rebuild history

When was the engine last rebuilt, by whom, and what was done? Ask for invoices.

How it was run

Diesels wear out from too little work as well as too much. A diesel that spent its life idling or at very light load can build up carbon and glaze its cylinders.⁴ Ask how the boat was usually run, and watch the engine at cruise and briefly at full throttle on the sea trial.

Questions to ask the seller

• How many hours, and when was the last rebuild? Who did it?
• When were the heat exchanger and exhaust manifold last serviced or replaced?
• Has the engine ever overheated?
• Where do you get parts, and who works on it?
• Can I take an oil sample and see a cold start?

Get an engine survey

On a trawler with an old diesel, have an engine surveyor or a mechanic who knows Lehmans aboard for the sea trial. See boat survey cost. Many classic Lehman-powered boats are Taiwan trawlers or Grand Banks; see our Taiwan trawler guide and Grand Banks guide.

Common questions

Is the Ford Lehman 120 a good engine?

It has a reputation for running a very long time when cooled and fed properly, and its mechanical simplicity makes it easy to understand. Condition and records matter more than the reputation.

Can you still get parts for a Ford Lehman?

Yes, through specialist suppliers that owners recommend, though lead times on some new parts can be long.¹

How many hours can a Lehman run?

With good care, many thousands. But hours alone don't tell you much on a 40-year-old engine. Look at the rebuild history, an oil analysis and how it runs under load.