Ford Lehman 120 vs. 135?

This may seem obvious, but...

Other than 15hp, what is the difference between a Ford Lehman 120 and a 135?

I see a lot of posts for the 120, not so many for the 135. At least it's still naturally aspirated, so no turbo troubles to worry about.

Are there any other idiosyncrasies? Are there any parts compatibilities - or are they completely different engines?

Ah yes,the 135 Super, neck whiplash from the tweaked up power increase. Lots of compatibilities, definitely not completely different. Others will know more but, the oil in the injector pump no longer required changing every 50 hours(not that everyone did, my manual actually said 200 hours). And, importantly, you must not retension the head studs.

BruceK said:

Ah yes,the 135 Super, neck whiplash from the tweaked up power increase. Lots of compatibilities, definitely not completely different. Others will know more but, the oil in the injector pump no longer required changing every 50 hours(not that everyone did, my manual actually said 200 hours). And, importantly, you must not retension the head studs.

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The manual was wrong. Bob Smith said in his seminar that start at 50 hours and see if the oil was diluted. If it is change the oil. If not push it to 60 and check the oil, if diluted change the oil. And so on but he recommended not going 200. He said every engine was different and to find out what your specific engine required.

There are a number of "updates" on the 135's vs the 120's. Injector pump oil circulated from the engine oil, improved head bolt and head gasket design, improved water pump shaft design, stainless steel exhaust water injection elbow, automatic closed cooling air bleed setup to name some.


Also, the injectors and fresh water pump are different.



Ken

I'm confused on the injector pump oil. CommoDave seems to be suggesting that the injector pump oil still needs to be checked periodically.

But Ken's response suggests that the injector pump oil is circulated from the main engine oil (so nothing extra to do here?)??

It would be nice to know that injector pump oil was one less thing to have to worry about.

On the 120s you need to do an injector pump oil change every 50 hours, maybe longer, on the 135s the injector pump oil is from the oil pan so it doesn’t need the separate oil change.

I think the 135 has engine coolant running through the engine oil and transmission oil coolers where the 120 uses raw water.

Also to change the alternator belt on the 120 you have to remove one of the main coolant hoses and replace the lost coolant. Many owners tie wrap a spare belt to the engine to prevent this issue if a belt dies at sea

John

Capt Jack said:

I think the 135 has engine coolant running through the engine oil and transmission oil coolers where the 120 uses raw water.

Also to change the alternator belt on the 120 you have to remove one of the main coolant hoses and replace the lost coolant. Many owners tie wrap a spare belt to the engine to prevent this issue if a belt dies at sea

John

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FL135 uses seawater for cooling in all 3 heat exchangers. Belt change on a 135 does not require removal of any hoses.

Ken

It sounds like there were a number of improvements from the FL120 to the FL135. I will certainly look forward to the neck whiplash PROMISED by BruceK in his answer!! (though really - would twin 90's get me to hull speed?)

Regardless of the power increase that I probably won't be able to notice - it does sound like the FL135's are a little easier to maintain. Not having to do a separate oil change for the injector pump will be a nice bonus!

Just wish that there were more of these engines on available boats in my area. And, looks like in Kemah, Texas area, there's primarily only one shop that likes to work on Lehmans (though that's better than what I found for turbo Lehmans, old Volvos, and maybe Perkins...).

Wonder what changed inside the injector pump. I thought the 50 hour oil change was to eliminate diesel in the lube oil. Now integrated into the sump means until next engine oil change a little or a lot of diesel may be in the whole system. Why is that better?

Good question but diluting a very small amount of diesel into 14 quarts of oil is better than diluting it into less than a quart.

Ken

kchace said:

Good question but diluting a very small amount of diesel into 14 quarts of oil is better than diluting it into less than a quart.

Ken

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Yes, but I am thinking small amount could also be large amount gone unnoticed. IF the 120 pump failed the overflow would show it quickly.
Same question, why is it better? (maybe leak issue solved)

Soo-Valley said:

Yes, but I am thinking small amount could also be large amount gone unnoticed. IF the 120 pump failed the overflow would show it quickly.
Same question, why is it better? (maybe leak issue solved)

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If you're good about checking oil level it's unlikely you'd get any major dilution without noticing it. The risk of diesel in the engine oil if the injector pump has a failure is common to many engine designs.

A diesel expert told that me the diesel section might be a separate section from the oil in that pump.

The 135s supposedly return a lot more fuel than the 120s and deliver more fuel for horsepower, so the pumps may have that separation mod with the oil flow through. The diesel does the lube for the upper section as it does for the injectors and why lubricity in diesel is important.

Soo-Valley said:

Yes, but I am thinking small amount could also be large amount gone unnoticed. IF the 120 pump failed the overflow would show it quickly.
Same question, why is it better? (maybe leak issue solved)

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I agree with the previous 2 replies and add: if the pump “failed” so badly, it 1. Would probably be noticed in impaired engine performance. 2. Would show up in rising oil level and 3. Injector pumps don’t normally fail in such a way to suddenly put large volumes of fuel into the oil.

IMO prudent engine maintenance should include oil analysis which will certainly catch fuel/oil dilution.

Ken

Gotta understand all the systems to see if an issue causing a change such as increased lube oil volume that is a known amount has gone to the danger range.

oak_box said:

It sounds like there were a number of improvements from the FL120 to the FL135. I will certainly look forward to the neck whiplash PROMISED by BruceK in his answer!! (though really - would twin 90's get me to hull speed?

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My twin P90's do indeed get me to hull speed. But not an inch/hour more.
Will probably install a head rest when I switch to 5 bladed props

psneeld said:

A diesel expert told that me the diesel section might be a separate section from the oil in that pump.

The 135s supposedly return a lot more fuel than the 120s and deliver more fuel for horsepower, so the pumps may have that separation mod with the oil flow through. The diesel does the lube for the upper section as it does for the injectors and why lubricity in diesel is important.

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psneeld said:

Gotta understand all the systems to see if an issue causing a change such as increased lube oil volume that is a known amount has gone to the danger range.

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I will go with what the expert told you. This was just for discussion as I have no plans to look for a 135.

On a FL120, there is no interface between the injector pump and engine oil supply. Therefore, the injector pump cannot be a source of diesel fuel in the oil sump. There are only two sources of diesel fuel into the lube oil. One is a failed diaphram on the mechanical fuel pump. If that happens, the oil sump will fill with fuel quite quickly. The other source is the fuel return pipe under the valve cover although a leak at one or more of the injectors would generally be very slow. I had this conversation with Brian at American Diesel just this morning. I called because one of my oil analyses came back with 3.5% fuel dilition but the lab said the oil was still good to use (241 hours). I called Brian to double-check. He said that wasn't anywhere close to being a problem especially with 241 hours on the oil. With the TBN still being above "7", the oil is likely good to use till 400, maybe 500 hours with a filter change.

Hey, don`t forget one of the main differences that make them go faster , as per Bruce, is the fact that that the 135 came with a chromed tappet (aka rocker) cover whereas the poor old 120 only had a painted one

Dumb question. How can I tell the difference between the 120 and 135?
My two six-cylinder engines are painted blue and have chrome valve covers. There are no serial numbers on either engine. The serial number tags are gone. The expansion tank is a replacement aftermarket. One weird thing is that the oil filter mounting is on the oil cooler, not the block. I have never seen this before.

All the 135's I've seen (including mine) have chrome valve covers.

Mine was a 120 that replaced a 135 but the previous owner used a bunch of 135 parts on the 120 block like the chrome valve cover so that's no guarantee.

Took over a year for American diesel and I to figure out what I had as many parts I described stumped Brian.

Finally, when I replaced hoses from the expansion tank to the heat exchanger (the long one starboard side that runs behind the injector pump)..... I finally found where they stamped the block with the serial number.

The serial number revealed that it was cast as a 120 block.

Brisyboy said:

Hey, don`t forget one of the main differences that make them go faster , as per Bruce, is the fact that that the 135 came with a chromed tappet (aka rocker) cover whereas the poor old 120 only had a painted one

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I waxed the cover on my 120 and gained 3 knots.

As psneeld described, there is a stamp on the block which will give you the info you need to determine the engine block's identity. The 135 has an inclined header tank for up to 15-degree inclined mounting of the engine.

A side question to this discussion. Not to hijack the thread. If we need to change the oil in the 120 fuel pump every 50 hours, which I do religiously. How do we follow Richard Bost and do extended cruising without shutting down in a high risk situation to change the oil? That’s an advantage to the 135 I would think.

Selidster said:

A side question to this discussion. Not to hijack the thread. If we need to change the oil in the 120 fuel pump every 50 hours, which I do religiously. How do we follow Richard Bost and do extended cruising without shutting down in a high risk situation to change the oil? That’s an advantage to the 135 I would think.

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What does the oil look like at 50 hours? If it isn’t diluted you can extend the interval. So I wouldn’t stop during the day to change the oil but rather wait til you stop for the night, if the oil routinely is good at 50.

If they have small oil lines running from the oil filter adapter plate on the engine block up to the injector pump they are probably 135s.
If the main heat exchangers are on the side they may be 135s.
If the main heat exchangers are on the rear they may be 120s.
If the injectors have side-mounted leak-off tube connections they may be 135s.
If the injectors have top-mounted leak-off tube connections on a large hex nut they may be 120s.
If the exhaust elbows are cast iron they may be 120s.
If the exhaust elbows are stainless steel they may be 135s.
The cam gears and injector pump gears are straight on one and angled on the other.
If they were assembled by someone from any available parts good luck.

I checked engine numbers

I am not limber enough to fit on the outboard side of the port engine, but the starboard engine block has the following cast in
PB T4 703F 6015BA
and the Ford logo

the port head has a stamp83F 6090GAB and the block has a stainless tag that says REF 3190 Type 120
Both engines are blue, have chrome valve covers that say Sabre on them, and the oil coolers (with the oil filter on top) also say Sabre.
Both engines have Bowman heat exchangers FH 420, with 2019 stamped on the serial number plate (cannot read the number) and the boat is a 1979.
so, what engine do I have?