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The base engine for the Ford Lehman 120 is the Ford of England Dorset diesel. This engine was developed in the late 1950s by Ford of England to be a heavy truck engine for which it proved a total failure. It did prove to be a good industrial and agricultural engine in applications where power requirements and operating rpm were both relatively low and constant. It was these attributes that brought it to the attention of a number of engine marinizing companies in England, Australia, and other countries including Lehman of New Jersey.

There was not a three-cylinder version of this engine so far as I know. There was a 90hp four cylinder version, the 120hp six cylinder version, and a 150hp turbocharged version. The 90 and 120 hp versions were both marinized by Lehman and were very popular powerplants in power and sail boats from the early 1960s until the late 70s or possibly even the early 80s, at which point Ford of England took the Dorset engine out of production.

I don't know if Lehman ever marinized the 150hp turbocharged version of the engine. I've never seen mention of any boat with one although it is covered in the original Lehman manual that came with our boat.

intersting. What i do know of the tractor version is that it was manufactured in england untill 1964 for export to the USA. After that they were made in the USA untill 1975 the last year of the tractor manufacture of these models. I will see if i cant find a connection on the tractor sites. They are both Ford engines so there must be a connection at some point

It used to be that all of Ford's diesel engines for trucks, tractors, etc. were made by Ford of England even if the vehicle they were going into was made in the US. They'd ship the engines to the US assembly plants.

This practice stopped at some point but I don't recall when and Ford (of America) started designing and manufacturing their own diesel engines in the US.

Ford of England made a wide variety of diesel engines for car, truck, industrial, and agricultural applications so there may well be no relationship at all between the 3-cylinder engine you're talking about and the Ford Dorset that is the base for the FL120. The Dorset was never manufactured in the US, for one thing.

The engine that replaced the Dorset was the Dover. British engine manufacturers tend to name their engines instead of just giving them a model number. In Ford's case they named the Dorset and Dover engines after the plants in which they were manufactured. Another example is Rolls Royce who names their commercial jet engines after British rivers (the Trent being the most current model).

The Ford of England Dover engine is also a six-cylinder inline diesel similar in basic layout to the older Dorset and it incorporates a number of improvements, not the least of which is a fuel injection pump that is lubed by the engine itself as opposed to the pump on the Dorset engine that has its own oil sump and oil change interval.

Lehman marinized the Dover engine, too (along with a lot of other companies) and this is the equally famous Ford Lehman 135 that was used in a lot of boats up into the early 90s I believe.

psneeld said:

hulll speed on one engine (plus the additional loss of efficiency by being on one engine)??

As a single guy, the second engine and around 50hp on the other one is all a waste in my mind...but that's just me...

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kinda agrees with my thoughts. I've ruled out this boat and am now considering a 41 defever with a single 120 ford lehman and a get home motor

bfloyd4445 said:

was the lehman a british design? I think this 3cylinder was originally a british design as well so u could be right.

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The "Ford" part is British, called a Dorset engine if I remember Marin`s post correctly.
The marinising part (Lehman) is American, not British. American Diesel supports the Ford Lehman engine these days.

RT Firefly said:

Greetings,
A particular vessel may use 4gph over a 200 hour season (average season I would say is 100hrs) versus one using 2gph. @ $4/gal that works out to be in the $1600 range.
Happy hunting.

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RT,
I don't know where you got the 100/200 hour average. I wouldn't think that's the average. Gives me an idea!!

At 25-30 tons and 240 HP (FL 120s) we are way overpowered as well but the solution for us is 1400rpm cruise and a slightly oversized prop to load the engines. 6.9 knots and 2.1gph.

Greetings,
Mr, Daddyo. Honestly, I can't remember specifically where I picked up that figure and it might be WAAY off. Must have read it somewhere but what would YOU guess is the average use of a vessel in a season? Of course boaters in northern climes would have a shorter season and retirees, I expect, would have longer seasons.

RT Firefly said:

Greetings,
Mr, Daddyo. Honestly, I can't remember specifically where I picked up that figure and it might be WAAY off. Must have read it somewhere but what would YOU guess is the average use of a vessel in a season? Of course boaters in northern climes would have a shorter season and retirees, I expect, would have longer seasons.

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I've always heard but often wondered about 200 hrs per year. Many Northeast non-fishermen are lucky to put on 100. I'm ure the Florida sportsmen make up for that....but who really knows?

Daddyo said:

RT,
I don't know where you got the 100/200 hour average. I wouldn't think that's the average. Gives me an idea!!

At 25-30 tons and 240 HP (FL 120s) we are way overpowered as well but the solution for us is 1400rpm cruise and a slightly oversized prop to load the engines. 6.9 knots and 2.1gph.

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I also read somewhere that the average boater operates his boat 100 hours. Dont remember were though

RT Firefly said:

I can't remember specifically where I picked up that figure and it might be WAAY off. .

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I don't think it is, RTF. I've been hearing that figure for average boat use ever since we got into this kind of boating back in the late 90s. The big GB charter fleet here quotes that number and I've heard and read it in countless places. I suspect it's pretty much on the money.

We are in a 2,000+ boat marina and I am told that we are among the relatively few people in the marina who use their boats year-round. The vast majority of boats in our marina--- just like the vast majority of private aircraft on an airport--- are rarely used. Exceptions are the charter fleets although come October their boats rarely move until the following June.

While the annual usage will vary with region--- in the northeast and Great Lakes many boats come out of the water for the winter where in Florida and California boats can be used year round--- based on what I see around us in our marina I would venture to say that even 100 hours per year is a generous figure for average cruiser use country-wide.

And even though we use our boat year round schedule and weather permitting, we only have time for weekend trips out to the islands. We take one longer cruise per year, two to three weeks, into BC. So even though we use our boat as much as we can--- and we go up and stay on it almost every weekend even if we don't go out-- we don't rack up that many engine hours.

My impression is that the typical boat owner takes his boat out zero to one time a year.

markpierce said:

My impression is that the typical boat owner takes his boat out zero to one time a year.

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a know several in the neighborhood of zero. I had one that for two years i paid for a covered slip and the boat sat on the hard. I've seen others with plants growing out of them at the marina from neglect.

Daddyo wrote;

"At 25-30 tons and 240 HP (FL 120s) we are way overpowered as well but the solution for us is 1400rpm cruise and a slightly oversized prop to load the engines."

That's 8 or so hp per ton and for most all semi-planing trawlers on this forum that is only slightly overpowered if at all. With my FD hull I'm slightly overpowered w 5hp per ton but only slightly and slightly overpowered is probably a good place to be. 1400rpm and over propped is not ideal but so many are doing it and not suffering significantly that I wouldn't urge you to change as long as you didn't start running at 2 or 300rpm down from max WOT rpm. But I suspect your boat was designed to run about 9 knots or so. Why don't you run at that speed?

markpierce said:

My impression is that the typical boat owner takes his boat out zero to one time a year.

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I think that's a very accurate and realistic observation Mark.

The brokers I've spoken with tell me 100-200 hours per year is what the average boaters engine run time would be. The harbormasters have told me they wonder if the average boater could find the slip it's tied up in.

If the harbormasters I've spoken with are to be believed then I agree the average boat is over powered. The average boat could go most of its life without an engine at all.

CPseudonym said:

If the harbormasters I've spoken with are to be believed then I agree the average boat is over powered. The average boat could go most of its life without an engine at all.

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Good point.

If we start talking averages, then the 30 yo one-owner boat I bought did 65 hours per year since new.

But, for the last 10 years it was well below that average based on both the reports from slip neighbors (fair enough, he was into his 80's...) and the amount of deferred maintenance.

Taking it a step further TC style, what do you think is the average ratio of maintenance hours to usage hours? Complicated by some usage hours somewhere nice on the hook used for maintenance.
I`m sure there are known figures for every type of aircraft, but what about boats. And is it an area we should not explore for fear of the result?
Now where is that piece of string...,and just how long is it?

healhustler said:

I really enjoy piloting my boat... Someone here on TF reminded me that my GPH had to be compared with my FPH (fun per hour). When I realized that my fun consumed only 2.2 GPH at 7.5 knots with my gennie running, I figured that my fuel cost for that was about 10 bucks per hour. What fun can you have these days at 10 bucks per hour?

If I was on Interstate 95, I could fight my way to average 60 miles in an hour, costing 12 bucks or so at 20 MPG. Heck, I'd give you the 12 bucks for the fuel and another 12 bucks on top of it just not to do it.

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hh - Bravo! Very Well Put!!

Bruce,
That's a very good one but hard numbers would not seemingly come foreword. All of us prolly have a rough est .... no .. could come up w a rough estimate of what those hours would be but actual?? ... Unobtainium.

Eric, FF, Mark:

My boat is a full displacement hull @ 55000 lbs with a LWL of 40.12'.

The engine is a Deutz delivering 145 HP @ 2500 RPM. I feel confortable with these numbers.
Wouldn't you?

Portuguese

I'm on the road w my I-Mac. How much hp per ton would that be? Sounds like you're just about right on the money. That's about the only way you can get a boat powered properly is to do it yourself. You should take pride in that you're one of the few that are not overpowered. Three cheers .. at least.

Answer to your question YES.

"The engine is a Deutz delivering 145 HP @ 2500 RPM. I feel confortable with these numbers.
Wouldn't you?"

YES! and with the fact that the Deutz is an industrial based engine.

"industrial based engine"

Fred, ... Why on earth would you mention that as all "marine engines" are from that source?

manyboats said:

"industrial based engine"

Fred, ... Why on earth would you mention that as all "marine engines" are from that source?

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are farm engines considered industrial? I believe many industrial engines are based upon agriculture designs and then the marine verions off of them. Farm engines live under the same conditions as a boat engine but industrial engines just run and run at the same rpm and load sometimes for years. I believe they are optimized for a certain load and rpm while farm engines are designed for heavy loads at diferent rpms. Never thought of this issue untill u brought it up. Sounds like a good topic for research

The Fl120 started as a truck engine, failed at that, became an industrial engine, succeeded at that, and then moved into agricultural applications as well. The marinized version is based on the base Dorset engine which was unchanged for truck, industrial, an agricultural applications. A Dorset was a Dorset.