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Old 09-12-2021, 11:23 PM   #1
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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?
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Old 09-12-2021, 11:33 PM   #2
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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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Old 09-13-2021, 02:37 AM   #3
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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.
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.
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Old 09-13-2021, 11:41 AM   #4
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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.



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Old 09-13-2021, 01:15 PM   #5
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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.
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Old 09-13-2021, 01:45 PM   #6
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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 doesnít need the separate oil change.
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Old 09-13-2021, 05:40 PM   #7
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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

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Old 09-13-2021, 07:47 PM   #8
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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

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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.

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Old 09-14-2021, 12:46 PM   #9
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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...).
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Old 09-14-2021, 12:51 PM   #10
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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?
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Old 09-14-2021, 12:56 PM   #11
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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.

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Old 09-14-2021, 01:04 PM   #12
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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
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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Old 09-14-2021, 01:19 PM   #13
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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)
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.
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Old 09-14-2021, 02:51 PM   #14
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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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Old 09-14-2021, 05:04 PM   #15
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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)
I agree with the previous 2 replies and add: if the pump ďfailedĒ so badly, it 1. Would probably be noticed in impaired engine performance. 2. Would show up in rising oil level and 3. Injector pumps donít 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.

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Old 09-14-2021, 05:14 PM   #16
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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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Old 09-14-2021, 06:18 PM   #17
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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?
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
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Old 09-14-2021, 06:21 PM   #18
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Originally Posted by psneeld View Post
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.
Quote:
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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.
I will go with what the expert told you. This was just for discussion as I have no plans to look for a 135.
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Old 09-14-2021, 08:12 PM   #19
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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.
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Old 09-15-2021, 04:53 AM   #20
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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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