Are 30 year old Lehmans any good?

[Afraid Knot]

Currently looking at a displacement boat with twin Lehman (6 pot) 120hp engines - yes slow and steady does it, but a couple of questions, at 2500 hours are they any good? Are spare parts readily available?

 

[gordmac]

I would think they would be fine as long as they have been looked after ok.

 

[TQA]

Big simple Ford diesels. 2500 hours is nothing. Expect 10,000 hours at least

But things like heat exchangers and exhaust elbows may be at the end of their lives. Check to see if the marine bits are available.

 

[Marsupial]

The basic engine should be fine and good for many more thousands of hours, crankshaft oil seals could be going a bit hard by now and could need attention.

The main injection pump should be ok as long as the oil is in good condition.

The main problems with the Ford were the ancillaries, they persisted in cutting costs on starters, alternators, water pumps, oil pumps and the fuel lift pump.

A common fault was leaking injector pipes, not a difficult or expensive fix.

A very basic check on condition is to ensure you have AT LEAST 30 psi oil pressure at idle with a hot engine, and no water in the oil.

 

[Afraid Knot]

Thanks all, sounds encouraging and the engines do LOOk as though they've been well maintained but I'd think I'd need some proof, Cheers all AK

 

[Greenheart]

Bit of a drift, here...I'd have thought 2,500hrs wouldn't be considered very much...seven hours per day for one year...less than many ferries/fishing boats must do...

...so, what exactly is the difference between commercial-grade marine diesel engines, and the standard marine variety which yachtsmen are familiar with?

Or, do commercial vessels routinely replace their engines?

 

[Marsupial]

Bit of a drift, here...I'd have thought 2,500hrs wouldn't be considered very much...seven hours per day for one year...less than many ferries/fishing boats must do...

...so, what exactly is the difference between commercial-grade marine diesel engines, and the standard marine variety which yachtsmen are familiar with?

Or, do commercial vessels routinely replace their engines?

in commercial grade everything is heavier, crank webs are thicker, bearing surfaces are larger, castings are thicker especially around the main bearings. bores are often chromium steel liners not cast iron, there will be proper bearings not just a cast iron machined holes, gears not chains, flywheels are often larger to help smooth out cyclic irregularity. Oil filters are bigger as are sumps. The engine is detuned to slog away for years at 1200 - 1800 (ish) rpm but still give good combustion and economy and a very long life. Some were built to be serviced and dismantled while they were running. At least that's what I used to make as a commercial grade engine.

power to weight ratio is no good for planing hull power boat

 

[Daydream believer]

Our dumper, digger & other low grade plant engines used to run for years with much abuse.
A marine engine tends to run at steady revs, temperatures etc & no sudden loads, high revs, acceleration etc unlike their land based counterparts
If the engines have been cared for with correct lubrication etc ( & how do you know ? That's the problem) then they should last years

 

[Greenheart]

in commercial grade everything is heavier, crank webs are thicker, bearing surfaces are larger, castings are thicker especially around the main bearings. bores are often chromium steel liners not cast iron, there will be proper bearings not just a cast iron machined holes, gears not chains, flywheels are often larger to help smooth out cyclic irregularity. Oil filters are bigger as are sumps. The engine is detuned to slog away for years at 1200 - 1800 (ish) rpm but still give good combustion and economy and a very long life. Some were built to be serviced and dismantled while they were running...

Wow! That would account for the prices, then. Good explanation, thanks.

I wonder why it is that marine diesels are said to suffer if they're run for long periods at less than their optimum RPM, but automotive diesels are very flexible without apparent problems?

 

[johnwest]

I have two of these in my boat. chatting about them with my engineer, his opinion was that they shouldn't need anything major until 70,00 hrs +. The only problems I have had was an alternator needed rebuilding and I have had both exhaust elbows replaced with bespoke stainless steel ones. I cruise at about 13/1400 rpm, about 7 knots.

j

 

[Marsupial]

I wonder why it is that marine diesels are said to suffer if they're run for long periods at less than their optimum RPM, but automotive diesels are very flexible without apparent problems?

modern automotive diesels (common rail) have some control over fuel requirements vs load - the agricultural lumps in boats don't do that very well the fuelling is a "best guess" sort of idea - so if you run them below the best guess optimum you can over fuel the engine.

If you run too cool all sorts of other issues arise - the worst is a sump full of bitumen and glazed bores. Now does sludge or low temp/low load running cause glazed bores? answers on a postcard please.

"Best Guess" is a design condition/requirement that probably never exists in service. is the cynical view!