Ford Lehman high rpm’s at idle

Hello all,

I am looking for a little advice as I am considering the purchase of a 1980s trawler. Overall the boat is in decent condition and has the options that I am looking for. The agreed to price is good as long as the engine isn’t about to fall apart. But here is my concern:

During the survey the engine, a Ford Lehman 120, was idling at 1000 RPMs (yuk) when it was first turned on, but during the sea trial it was idling back down at 650 RPMs where it is supposed to be.

So my question is this - where on the scale of problems does this issue probably fall, from checking filters and oil all the way to an engine rebuild.

Is this a run from the boat as fast as you can problem, or is this just one of the many engine type problems that trawler owners are faced with and have to deal with from time to time?

I do realize there are multiple possible causes for this issue; so maybe the better question is do any of the more likely causes require an engine rebuild?

I did find that the surveyor addressed this in the report with:
“Adjust the control cables and fuel rack if still needed. The idle should be 600RPM.”

In case any of this information is relevant, I heard the previous boat owner hit the boat for 20 years and took decent care of it. However, the current owner has had it for 2 - 3 years and my impression is that he spent very little time on the boat due to family issues. And in this regard, all of the filters needed replacing and the oil changing.

I did order oil samples to be tested, but have not yet gotten those results.

Your thoughts are most welcome.

Bill

I would not be too concerned. Worse case you might be faced with replacing or rebuilding a fuel pump if other adjustments don't resolve it. But I suspect it is just in need if an adjustment or it was due to minimal operation over time. I don't think it could in any way lead to an engine rebuild. These engines are solid!

How many hours on the engine? Maintenance records? I would surmise a simple adjustment, or cable replacement, or as Ready suggests, worse case, rebuild fuel pump which on those engines are fairly easy.

Thanks for the feedback Ken.
I’ve heard great things about these engines.

Weirdly enough I have a tiny bit of experience working on these engines which was imposed on me by my dad. My memories are of being a lad of 6 or 7, it being night and my hands freezing as my sole task was to clean the various tractor innards dad handed to me with a wire brush in a bucket of gasoline in an unheated barn. Much to my dad’s chagrin I never had the desire to become a mechanic. I suspect, at the very least, he is having a bit of a chuckle right now.
: )

There are 2000 hours on the engine and supposedly rebuilt in 2005.
There were maintenance records available but I failed to get a good look at them in the short time I had with the boat.

Many diesels I have come across have a high idle to start the warm up process, I wouldn't worry at all.

Not sure if Lehman injector pumps have that as a built in option, but if it comes back to the 600 range after some warmup...I say it's not a bad thing...maybe even a good one.

My twin Lehman SP225's have a higher idle at start and lowers into range as they warm up. As long as your oil analysis comes back good you should have no worries.

Never hurts to check cables for proper adjustment and excessive wear though.

Should idle around 750. Can vibrate a little below that. Mine idles at 650, but is not as smooth as 750. From 750 on no vibration at all from drivetrain.

Thank you for all of the replies and helpful insight! I hope to be joining this forum as a trawler-owning member within the next month. fingers crossed. : )

My 120's have 4,000 hrs on them. Rock solid engines. Changing the engine and tranny coolers is a piece of cake, get t he hose kit from American Diesel also. If you call Brian at AD and provide the serial numbers he can provide some history of purchases going back yrs.

I seem to recall that there was a cold start /excess fuel option on some of the injection pumps. Would cause that.

To get any info on any FL engine you NEED to go to Brian at American Diesel.
His dad developed the line. He KNOWS the engines. He also has most parts.
804.435.3107

Another great info/parts source for Lehman engines is (at least was) ... Bomac Engeiineering in GA, USA

@bill209
Well did you but this boat?

SteveK said:

@bill209
Well did you but this boat?

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Heh....
I was wondering the same thing...

Hey guys!

So sorry I did not follow up - things have been a whirlwind … because I did buy the boat!

I’ve now gone through the North channel and into the St. Lawrence river and the engine has been purring along great.

I can’t say the same thing about the generator, the toilet,….

Thanks to everyone for the responses and support!

Good to hear, good to see you're having big fun!

Yeah, the toilet...had to replace both before we took the "re-homing" cruise -

Ah, boats.

Choices said:

Should idle around 750. Can vibrate a little below that. Mine idles at 650, but is not as smooth as 750. From 750 on no vibration at all from drivetrain.

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Agree on smoothing rpm. Anything less and the 120s on my previous boat wanted to come up to the helm to see what was going on.

Nepidae said:

To get any info on any FL engine you NEED to go to Brian at American Diesel.
His dad developed the line. He KNOWS the engines. He also has most parts.
804.435.3107

Click to expand...

You were so spot on. Brian was extremely helpful; he pulled the information I was looking for from a microfiche, which has nothing to do with a poorly developed aquatic animal for those who are under 50. : )

Congrats on the boat purchase. Brian is indeed the go to guru on the Lehmans. Have fun with the new boat.

Why do i think that these engines have the fuel injection pump that requires oil change!

DrissZougari said:

Why do i think that these engines have the fuel injection pump that requires oil change!

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The 120s do have oil that is separate from the engine oil sump so the oil needs to be changed. The 135 and other Lehmans do not need injection pump oil changes separate from the engine oil.