Ford Lehman Fuel Consumption after Overhaul

I have a single Ford Lehman engine not turbo charged, 120 hp, 2703E newly overhauled by a reputable firm. The cylinders were bored out 20 thousandths so the engine now has new pistons, rings and connecting rods along with a substantial list of other improvements, including an overhaul of the injection pump and replacement of the engine oil cooler, coolant heat exchanger, and transmission oil cooler in addition to a transmission overhaul. Before the overhaul, the engine used 1.6 gallons per hour. Now, after the overhaul, it uses 2.7 gallons per hour. I was under the impression that it would use less fuel. It also smokes as much as ever, maybe even more, and there’s a substantial oily sheen in the wet exhaust. Is this to be expected? The engine leaks oil around the transmission adapter flange so I need to add a little oil about every 10 hours. The coolant level doesn’t vary. I carefully followed and recorded the break in process as described in the FL manual. I recently polished the fuel. After the break in I have, as usual, operated the engine at 1800 rpm, +/- 7 knots. When fully loaded with water and fuel the boat, a square chined 1968 Grand Banks, weighs about 22,000 pounds and is 32’ long with 11’ beam. The one improvement besides running at all, is the engine starts beautifully, within a couple seconds. The engine now has 107 hours on it. Is it possible that some adjustment is out of whack? Although the price for the work was, in my estimation, very fair, I’m nonetheless disappointed after all the hassle and expense because now my range is greatly decreased and the boat is more expensive to operate. The firm I used to overhaul the engine is operated by a busy man of few words who more often than not fails to answer my emails. So, I ask you, do you have any thoughts? I should add that I already asked Brian at American Diesel and he said “Any rebuilt engine is going to require a "break-in" period, during which the actual rates of consumption will vary”. Thanks for any input or advice you may be inclined to add!

I have nothing valuable to add, other than being interested to see what more knowledgeable folks have to say about your situation. And I hope everything turns out OK for you!

Moonfish, thanks for your interest. Bloody well perplexing, this. It might turn out that patience is the solution to the problem. I will post if the fuel consumption decreases with the addition of more engine hours. Wouldn’t that be nice! Thanks again

How are you measuring fuel consumption?

I would expect the Lehman would be well past any 'break in' period and the fuel consumption seems excessive. A rebuilt engine should not smoke and should not leave a sheen. Have you done a compression check to make sure rings are seated properly? Was the High pressure injection pump rebuilt by an injection shop or by the engine mechanic? No idea on how to measure fuel pressure out of pump but I suspect any injection shop could do it. Assume injectors were also rebuilt. Might be wrong nozzle size. Again, an injection shop would have capabilities of checking them. Assuming he did valve seats at a minimum. Always a good idea to check valve adjustment. It's a quick check.

Once you have checked compression and valve timing you are left with injection system and that is beyond the capabilities of the average toolbox. Send them out for a definitive analysis. Brian should have the original specs.

I'm dipping a marked measuring stick in my fuel tanks.
I've measured all the dimensions of the tanks and have calculated how many gallons per inch the tanks have. Lets say I've made a mistake in my measurements or calculations. Even if that were the case, there's a very discernable difference in fuel consumption before and after the rebuild.
Thanks for your inquiry

I haven't done a compression check. I reasoned that because it starts so quickly, that the compression was good. I will keep your good advice in mind however. The injection pump was rebuilt by a company that does Lehman rebuilds all the time. I don't know if the injection pump was rebuilt by an injection shop. I'll look around our area to see if anyone has experience measuring fuel pressure from the pump. I was told the injection nozzles were replaced. Once again, this shop rebuilds Lehmans all the time. I was told they did a valve job also. I had the valves adjusted after the 15 hour break in period as the manual directed. Thanks so much for your input SoWhat. It's very valuable to me. Much appreciated. I'm heading out on a boating foray tomorrow but will post any information about how this problem shakes out. Thanks again.

many different Lehman models so easy to put in a wrong nozzle with larger ports. Would kill fuel economy. On a total rebuild I would want the injectors completely rebuilt. Not just nozzle replacement. Does a valve job entail lapping the old valves to the old seats? or replacing all valves along with new seats. A detailed invoice if they supplied one should give you the information you require.

An experienced mechanic would catch wrong sized rings but errors happen. A compression check should eliminate the question. I agree that quick starting makes it unlikely but I run through all the standard easy checks'

You might want to hold some paper towels at exhaust and then do the smell test, Is it engine oil or diesel. Most likely diesel due to consumption but it pays to check.

Smoking a little and exhaust sheen is normal even for rebuilds.

1.6 gph at 1800 rpm on a boat like that I would say low, closer to 2. 1 +/- gph is more common in my experience. That is both tank measurements and people reporting using flow meters.

Mine burned 1.9 gph at 1650 +/- rpm for the last 20,000 NM, engine hours from rebuild plus 200 to around 3700 hrs.

Using tank measurements can vary a lot depending on how often you throttled up and down and sea conditions.

I have no idea as I am not really an engine guy, but my gut says injection pump or injectors, especially if you are truly seeing a lot more smoke and sheen.

My rebuilt Lehman 120 didn't fully settle in until it topped 200 hours. Purrs now. Had some exhaust sheen that went away and it runs clean now. Well, as clean as a Lehman runs.

Thanks again SoWhat for your additional insight. Very helpful. I will do a compression check when the off season arrives. I’m reasonably certain they put in new valves in addition to redoing the valve seats. Will also check to see that the sheen in the wet exhaust is actually diesel.
I ran into an old salt today that had more interesting insight. He said when a shop does a rebuild of a diesel engine which includes an injection pump rebuild, they will normally adjust the pump toward a rich mixture to provide extra lubrication for an extended break in and that it should remain that way for several hundred hours before adjusting the mixture to more lean. That might go a ways to explain the smoke and sheen.
Thanks again!

Thanks psneeld for your very helpful information. I’m beginning to relax a little bit with your input in mind. If you happened to have read my most recent reply to SoWhat, your guess about the injection pump being the problem sincs well with the old salt’s explanation of a standard factory injection pump adjustment toward a rich mixture for extra lubrication during an extended break in period. Thanks again!

Thanks hobbystuff for your input. You’ve done a lot to put my mind at ease with your explanation. Much appreciated!!

IF the gov is set for a "rich mixture" too overload the oil scraper rings ,

I think oil changes should be more often.
A an oil sample test will clarify the issue.

Usually the hone marks on the cylinder walls provide all the oil required for cylinder lubrication.

How many hours before the rebuild?

Hi Kenhuse, just curious, how many hours did that Lehman go before you had to have it rebuilt? Thanks.

My 135 Lehman burns 7lt an hour at 7knts pushing a 20 tonne displacement trawler at around 1200 rpm ..... purrs like a kitten day in day out around 500hrs since rebuild ..... originally did over 8000hrs ..... wouldn’t have anther motor in the boat ?

paulpoz said:

Hi Kenhuse, just curious, how many hours did that Lehman go before you had to have it rebuilt? Thanks.

Click to expand...

When I bought the boat in 2012, there were 6 hour meters for various things and none of them worked. The previous owner used the boat as a live-aboard and kept no records. So..... I haven't the foggiest notion how many hours were on the engine before the overhaul, sorry. I can tell you that the hone marks on the cylinders were long gone.

Mobcat said:

My 135 Lehman burns 7lt an hour at 7knts pushing a 20 tonne displacement trawler at around 1200 rpm ..... purrs like a kitten day in day out around 500hrs since rebuild ..... originally did over 8000hrs ..... wouldn’t have anther motor in the boat ?

Click to expand...

I love the report on your Lehman!
However, you have a boat that weighs almost twice as much as mine, with a bigger cubic inch engine and it burns 7lt/hr at 7 knts. at 1200rmp, whereas my engine currently burns something like 11lt/hr at 7knts at 1800rpm. I'm not sure how to sort this information out. Does the evidence suggest that I should run my engine at 1200rpm? I'm at the end of the boating season here in SE Alaska so will now pursue the various investigative measures suggested in this helpful thread to find out more. Thanks for your reply.

40% more fuel is a lot. Since the engine was out, I'd check the alignment. A bad alignment will increase fuel consumption. The average marina mechanic doesn't take the time to do a good alignment.
Depending on the skill of the rebuilder, the bearings and rings could be tight. A lot of rebuilders are parts changers, only. Many automatically turn down the crank, buy undersized bearing and slap things together. Every machined part, bearing, ring and piston has a manufacturing tolerance. People that don't take the time to measure journals and bearings often turn down cranks that are still standard. Most diesel engines I've rebuilt, that had good maintenance, still had standard cranks. I've seen lots of 50 year old cranks with zero measurable wear. But when you arbitrarily turn down cranks, and just order undersized bearings, you enter the world of manufacturing tolerance. A .010" undersized bearing could be anywhere from .008" to .012". When you measure everything, you find these things out. The crank could be a little big and the bearing shells a little thick. Until the bearings wear a little, you could have a tight engine that will consume a little more fuel. Same for the pistons, rings and bores. You may see elevated levels of bearing material, maybe iron, in oil tests for awhile.

Thanks Lepke for the information. Theres a lot there. Much appreciated. I just changed the oil and set aside a sample to send off. I’ve personally checked the alignment 3 times. I’m not a professional by a long shot but estimate I’ve got a reasonable feel for that task. There’s also no vibration that seems beyond the normal engine vibration, as far as I can tell. Thanks again!

Kenhuse said:

I love the report on your Lehman!
However, you have a boat that weighs almost twice as much as mine, with a bigger cubic inch engine and it burns 7lt/hr at 7 knts. at 1200rmp, whereas my engine currently burns something like 11lt/hr at 7knts at 1800rpm. I'm not sure how to sort this information out. Does the evidence suggest that I should run my engine at 1200rpm? I'm at the end of the boating season here in SE Alaska so will now pursue the various investigative measures suggested in this helpful thread to find out more. Thanks for your reply.

Click to expand...

Depending on how your propped I suppose , but mine will only do 1800rpm wot and would probably slurp around your litres per hr up in your current range , I rarely go WOT mostly only the last 15 minutes of a voyage to let her burp and clear her throat , it just seems pointless for to go anther 600-650 rpm WOT to gain maybe anther knot in boat speed but basically double the fuel burn and she’s just so happy at 1200-1250 rpm and very quiet ? ??

she’s just so happy at 1200-1250 rpm and very quiet �� ����

Sounds like you have the proper prop for cruising.

Mobcat said:

Depending on how your propped I suppose , but mine will only do 1800rpm wot and would probably slurp around your litres per hr up in your current range , I rarely go WOT mostly only the last 15 minutes of a voyage to let her burp and clear her throat , it just seems pointless for to go anther 600-650 rpm WOT to gain maybe anther knot in boat speed but basically double the fuel burn and she’s just so happy at 1200-1250 rpm and very quiet ? ??

Click to expand...

Boldly exposing my lack of knowledge and or imagination after trying to guess but failing, I have to ask, what’s WOT? Thanks Mobcat

Wide open throttle

John

Thanks Captain Jack!