How Many Ford Lehmans are there?

Yup * *....ther'e heat engines and w a mixture of 60-1 *40-1 can't make much heat. Gas is about 15-1 ALL the time so gets real warm at even low power. That's the main reason diesels are more efficient and as they near full throttle i'm told they're about the same * *....in efficiency. It takes me at least 10 min of running before I'm up to cruise speed but unlike Bob Smith I like to let the engine run at least 2 min before putting in gear. Seems I frequently disagree whith that guy. This point is fly stuff though.

A couple of years ago we siezed one of our Lehman 120 engines, and to this day I don't know how we managed to do it. We left the overnight mooring and headed home, about 30 minutes after starting the motors the port egine warning oil temp buzzer came on, we shut the engine down and came home on the starboard engine.

Our mechanic, the best Lehman man in our part of the world, went over the engine and eventually found the problem. One of the pistions had melted to the top of the cylinder head, the impeller had some damage but was still recognisable as an impeller,water strainers appeared OK, in short we had no idea what caused one of these 'bullet proof'engines to melt in such a short time. Just wondering has anyone ever come across anything similar

Hiya,
** Mr. shrimp.* Just out of curiosity was the melted piston the one at the "front" of the engine?* ie: the one furthest from the transmission?

I would guess it was #6. Melted?

Hiya,
** Can't remember the cylender numbering.* Is #6 at the front?

I think you're on the right track, Rufus

I was told by several "experienced timers" that #6 is the one that will overheat.
Bob Smith was NOT one of them.

I actually have most of my lines free before I fire up the diesel. I walk aft, verify water out the exahust, climb on the bridge and by then the first mate is freeing that last lines.
So I'm probably running for 1* to*1 1/2 minutes max before I cast off and idle to 1100 rpm and 5 knots *down river. 20 minutes later I am where I can "power up" and do my 6.5-7 knots.
So far no cervical strain injuries from acceleration.*

Hiya,
** The reason I'm asking which is cyl #6 is if it is the one on the front of the engine, one of the problems with the 120 Leman is an air pocket accumulates at the upper end of the exhaust manifold and that pocket should be eliminated on* a regular basis by opening the small "petcock" at the upper end of afformentioned manifold and allowing antifreeze to drip out a bit.* This can be hastened by loosening the rad cap on the expansion tank.
** If this air pocket is allowed to remain, the cyl adjacent to it (the one at the front of the engine) will run very hot possibly leading to piston melt.
** How many of you Lehman owners do this bleeding on a daily basis?

nomadwilly wrote:....ther'e heat engines and w a mixture of 60-1 *40-1 can't make much heat.

Click to expand...

For all practical purposes there is the same heating value (energy content) per pound of gasoline as there is in diesel fuel.

leaning the mixture produces higher, not lower temperatures. The combustion gas temperature in a diesel engine and a gasoline engine is about the same.

The reason a diesel is more efficient is because it converts more heat to work.* It doesn't blow it out the exhaust so less fuel is required to do the same work.

shrimp wrote:the impeller had some damage but was still recognisable ... we had no idea what caused one of these 'bullet proof'engines to melt in such a short time.

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Hmmmmm .... do you think the melted piston wrecked the impeller?

Just a refresher question, what does the impeller do?

*

Couple of things:
On the Lehman 120-
#6 is the REAR cylinder, and yes that is the one that has a known heat problem. It will overheat if the engine is ever starved of cooling water. BEWARE. On my engine, it shows more heat there as the paint doesnt stick there very well.

The air pocket phenomenon is a real one but easily remedied. There is an air bleed valve on the top of the exhaust manifold. When filling the coolant header tank, open this bleed valve until all fluid comes out, then close it. Never need to bleed it again.
Bleeding is ONLY needed when changing coolant or if it was drained.

R,

No Rick. You can fry your breakfast on the exhaust manafold of an iddling gas engine but a diesel is very cool*** ...compared. The only way to "throttle" a diesel is to vary the amount of fuel injected and at idle thats very little (60 to 1 as I cecall). Leaner and richer in a gas engine is very small differences * * .... in a diesel it's huge. Diesel engine like diesel stove** ...more fuel more heat.

"leaning the mixture produces higher, not lower temperatures."
In a gas engine.

"The combustion gas temperature in a diesel engine and a gasoline engine is about the same."************** At or near full power only.

"The reason a diesel is more efficient is because it converts more heat to work."
Because it takes less heat to do the work at lower power settings.

"For all practical purposes there is the same heating value (energy content) per pound of gasoline as there is in diesel fuel."***** Got that one right.

"(60 to 1 as I cecall"

Some are even leaner at idle.

Lean (less fuel)*in a diesel means less power. More fuel than can be burned makes heat in a diesel. When you see black smoke out the pooper your EGT is climbing out of spec most likely. If EGT skyrockets your coolant gages won't tell you this at first, as it takes time to heat soak the engine. By the time the coolant temp rises to be noticable you may have already cooked something (ie number 6).

Any engine that is not level, and most in a boat are not, runs the risk of developing an air pocket in the cooling system if it is not proprly vented.

Considering that the fuel and air in the cylinder of a diesel engine do not form a homogenous mixture, the concept of rich or lean is not really applicable.

The spray of diesel fuel burns "rich" in some areas and "lean" in others. The fact that a large weight of excess air is present in a diesel engine at low power settings is one of the reasons why most diesel engines are less thermally efficient at low power, a lot of heat is absorbed by the charge air rather than doing work.

It doesn't matter if you are burning gasoline or diesel fuel, a lean mixture burns hotter than a rich mixture.

"Because it takes less heat to do the work at lower power settings."

That is actually backwards, nomad. Because the pumping losses and mechanical losses are essentially the same at low power as at high, more energy (heat) is required per horsepower or kW at low power than at high power. That is why FF is half right, the BSFC at low power is higher than at 70 or 80 percent for example.

The exhaust on an idling gas engine is very hot because spark ignition engines don't have very efficient combustion processes and idling is among the worst conditions it will ever see. To provide a mixture that can be ignited by a spark, and burn without detonation, it has to be rich. More fuel has to be in the cylinder than the engine requires to rotate and the excess heat goes out the pipe.

A diesel only requires enough fuel (heat) to overcome pumping and mechanical losses. It* uses nearly all that heat to perform work. The combustion products cool by expansion so the exhaust is cooler than a spark ignition engine.

A lot of people confuse what happens in a gasoline engine and a diesel engine. The process is not the same.

-- Edited by RickB on Tuesday 19th of October 2010 02:00:04 PM

ralphyost wrote:

There is an air bleed valve on the top of the exhaust manifold. When filling the coolant header tank, open this bleed valve until all fluid comes out, then close it. Never need to bleed it again.

Click to expand...

We crack this bleed valve before every cold start and leave it open until we get fluid out of it.* We always get a few bubbles of air before the fluid (same on both engines).* To do this the cap on the header tank needs to be off or at least open, otherwise no fluid will come out of the bleed valve.

The bleed valve should never been opened when the engine is running or hot.* Checking the valve periodically on a cold engine*does two things--- it ensures there is no air buildup and it keeps the valve "limber" for the day you truly do need it such as when changing coolant.

Hiay,
** I agree fully Mr. Marin* and it's part of my daily morning engine/fluid check.* ATF, oil, belts, leaks, AF, batt's, stabilisers (fluids,etc.)...takes about 10 mins....That along with 2hr, or so, regular ER checks.
*** Keep on truckin '...hahahahaa....so 70's

-- Edited by RT Firefly on Tuesday 19th of October 2010 02:28:54 PM

In regard to the melted piston I think it was either the aft or second to aft piston,ie closest to the gear box. Mentioned the impeller on the raw water pump to discount circulation issues with the raw water cooling system.Interestingly when we brought the boat into dock the mechanic was there within 15 minutes and managed to start the port engine and checked that it was still pumping out through the exhaust.That's when he told me it didn't look to bad ,maybee a head issue.HA!, $24,000 later- thankfully I have a very understanding insurance company.

When we bought Sarawana it was our first time with 2 engines, our previous boat was a Clipper 34 with a single Lehman,so we got a professional skipper to take us out for the day to teach us the in & outs of the new mighty twin. He showed us how to the bleed engines, unfortunatley he forgot to tighten the bleed screw up properly, and after about 10 minutes of running the engine warning buzzer sounded.After shutting down the motor we took a look in the engine bay to find covered top to bottom with our fresh water coolant, so he tighened the screw and filled the header tank from our deck wash hose,which as we discovered later, unlike our old boat, was seawater.When our mechanice found out he went 'off' bigtime, gave him a mouthful the sent him the bill for flushing out the engine and wasting his time. Don't you just love boats, and the slightly deranged mob who own/look after them.

"so we got a professional skipper"

Doesnt sound so "professional" to me !

Remember - just because someone takes your money for service does not make them PROFESSIONAL.

R.

"In regard to the melted piston..."

If the impeller that is still recognizable as an impeller pumped enough seawater to cool the engine then carefully inspect the injector on that cylinder.

A blown tip or severely eroded nozzles will dump fuel straight onto the piston crown and the torch effect will quickly melt an aluminum piston and will also destroy a cast iron one as well.

Make sure you have all of them checked and carefully inspect all the other pistons as well.

Thanks for the advice, as the port engine has now been fully rebuilt, I guess i will never know for sure what caused the problem, but I do occassionally glance over at its stable mate on the starboard side and give it a reassuring pat to encourage it not to follow in the footsteps of its errant friend.

Hello friends, two SP 275 Lemans on my IG 36.

sorry ! Lehmans...

LeMans are good too

I just found these pics of my former Lehman, a 90 in my Albin 27.

-- Edited by Daddyo on Monday 15th of November 2010 11:28:54 PM

"LeMans are good too"

I once owned a 1962 Pontiac LeMans and I'm not sure I would agree......LOL
Although the lesson I learned from it when I was 16....and it's a major lesson....
when you walk up to your car and see bolts lying on the ground under it...do NOT run it.
(10 miles later I realized they were harmonic balancer bolts...that was when a rod blew out)

"(10 miles later I realized they were harmonic balancer bolts...that was when a rod blew out)"

Most every diesel in the world also had a harmonic balancer, most are rubber and die in time.

Anyone ever bothered to replace it , 30 to 40 years for rubber IS a long time.

FF

I think a harmonic balancer was an option upgrade on my engines, either that or who ever set them was tone deaf.My old Lehmans are definatley more 'shake ,rattle & roll'. Actually I am quite fond of them.

Question though. I have two 120 hp Lehmans, the starboard engine heats the fresh water for showers etc but it is very slow and does'nt really do much more than warm the water. On my previous Clipper 34 ,also a 120 hp Lehman, the water would heat up nicely in about 40 minutes under cruising conditions. Anyone have any ideas of what the problem may be.
Thanks.

shrimp wrote:

I think a harmonic balancer was an option upgrade on my engines, either that or who ever set them was tone deaf.My old Lehmans are definatley more 'shake ,rattle & roll'. Actually I am quite fond of them.

Question though. I have two 120 hp Lehmans, the starboard engine heats the fresh water for showers etc but it is very slow and does'nt really do much more than warm the water. On my previous Clipper 34 ,also a 120 hp Lehman, the water would heat up nicely in about 40 minutes under cruising conditions. Anyone have any ideas of what the problem may be.
Thanks.

Click to expand...

One word.* Thermostat.* Either to low of a temp setting (160*)*or not working properly.

*

shrimp wrote:

Question though. I have two 120 hp Lehmans, the starboard engine heats the fresh water for showers etc but it is very slow and does'nt really do much more than warm the water. On my previous Clipper 34 ,also a 120 hp Lehman, the water would heat up nicely in about 40 minutes under cruising conditions.

Click to expand...

Our boat has more or less the same setup.* Make sure the send and return lines from the engine's coolant system are not clogged or partially clogged.* One indication that this might be the case is if the starboard engine gets up to temperature fairly quickly, almost as quickly as the port engine.

While all hot water heaters are different, our ten-gallon Atlantic Marine tank only has a thermostat on the elecrtric heating element.* There is no thermostat on the engine*coolant heat exhanger inside the tank.* If your water heater has some*sort of thermostat on the engine coolant heat exhanger, that could be defective.

Make sure there's no valve/petcock on the side of your Lehman that could be restricting the flow of coolant through the hot water heater loop.**Our starboard engine has*a petcock on the connection of one of the hot water heater coolant hoses but it's*outboard of the hose connection and of course is always closed.* Otherwise all the*coolant would drain out of*the engine.*

Andy,
Like Marin says you could also have a restriction. If you have access to an infared heat gun you could "shoot" the temp at about a foot away from the engine on both hoses and they should be about the same temp as your thermostat housing on your engine when you reach operating temperature. One hose cooler than the other would probably indicate a blockage in your WH.
If that is the case- and you can determine the flow of your engine coolant to the WH (that hose should heat quicker than the other), then you may be able to "backflush" the WH and clear it out.