Warm up 120HP lehman

[rslifkin]

Generally for most engines I stick to a guideline of no more than 40 - 50% throttle, and no more than 40 - 50% of max RPM until full coolant temp. Then 50 - 60% is acceptable for a few minutes until the oil gets up to temp, then go for it. This guideline applies to cars, boats, etc.

For engines without a temp gauge, it's a bit different. The boat generator gets 2 - 3 minutes of un-loaded warm up, then apply load. Keep the load below 50% for another few minutes while it finishes warming up. Dinghy outboard gets a minute or so before departing if it's cold (hasn't run in a few hours), then keep it under 3000 RPM for a minute or 2 after departing. It's a small engine, so it warms up fairly quickly.

Long, slow warmups at idle with no load aren't good for any engine, as it spends a long time running in a sub-optimal state. Better to raise the idle a couple hundred RPM until you're ready to go (gets combustion temps up a bit and gets better oiling to the valvetrain, cylinder walls, etc.).

I usually bring my engines to ~1100 at startup. Being gassers, they usually creep up to ~1200 after a minute or so as the chokes start to open. They'll creep a bit further if left to warm up more, but by the 1 - 2 minute mark we're usually throttled back to idle and departing the dock (or pulling up the anchor). For comparison, normal idle when fully warm is just over 800 in neutral, ~700 in gear (a little under if in gear tied to the dock, just over 700 when moving). Idle is a little lower (50 RPM or so) when cold.

 

[psneeld]

Some diesels in cold enough water take forever to even start coming up in temp if left at idle.

 

[Mambo42]

Again, unless specifying a particular load and what exactly are "higher RPMs" whether seconds or 15 minutes warmup really is just a matter of guessing/opinion/difference/whatever.

The way it was explained to me made a lot of sense when I thought about it later.
All the heat in the engine is primarily generated at the point where the diesel is ignited, read the top of the cylinder. This causes the metal around that spot to warm up rapidly while other parts of the engine can still be cold. What you get is huge differences in temperature within the block itself and that causes metal stress in the block.
When you heat up the engine slowly the heat of the ignition of the diesel gets dissipated throughout the block. However when you instantly go to 2000 rpm the spot temperatures in the block get higher, after all, the higher the rpm the higher the temps will be.
It is one of the reasons why large cargo ships don't like to change RPM's either, the engine runs at a set RPM and the temperatures in the block are constant. If they would do powerbursts they would create high spot temperatures in the blocks and thus reduce the life of the engine.

Now, this whole explanation does make a lot of sense to me. Will slowly warming the engine help my engine ? No idea, but it also doesn't hurt it, so that is why I warm up the engines slowly to operating temp.

 

[psneeld]

Have at it, I don't dispute your points, I just believe diesels are built to withsyand some of the thingscyou are discussing.

If I strongly held those beliefs, I would run block heaters for every night before departure. My engine just would take forever to come up to temp Nd at 6.3 knots cruise, days were ling enough as it was.

Plus I didn't need my engine to last 30 more years like some here imagine, I probably won't live that long , let alone cruise that long.

Plus in the previous 50 plus years most Lehman blocks have survived was worse operators than me.

 

[rslifkin]

Hot spots, etc. are a concern, but you definitely don't need super slow warmups, etc. to avoid them. Just keep the loads light until it's good and warm, let it idle for a minute or 2 before shutdown if it's been under heavy load recently, etc. If you motored through a no wake zone a little above idle for a couple of minutes before docking and didn't use much throttle for maneuvering, then it should already be cooled enough and can be shut down safely once you've got the first few dock lines secured.

Thermal stress is more of an issue on really big engines than reasonably sized ones. Remember that during a long warmup, it's spending more time running with the pistons, cylinder walls, etc. below normal temperature and therefore not at their normal tolerances, so that increases wear. A little bit of load will get things up to temperature much faster. Personally, I think wear from extended no-load warmups is likely to be worse than any wear from having a little bit of load applied to a cold engine.

 

[SteveK]

more importaant than warmup is oil circulation. Shut down an engine and most oil will drain to the sump. No wonder wear and tear is greater at startup than running. So part of the operation done with light loads gets the oil to all points of the engine.
Now pedal to the metal time.

 

[rslifkin]

more importaant than warmup is oil circulation. Shut down an engine and most oil will drain to the sump. No wonder wear and tear is greater at startup than running. So part of the operation done with light loads gets the oil to all points of the engine.
Now pedal to the metal time.

Yup, and that's also why the little bit of runtime between start and departure should be at somewhat above idle RPM. Certain components aren't directly pressure fed oil (such as cylinder walls and sometimes wrist pins), so with cold, thick oil, they may not get much oil sprayed / splashed onto them at idle. A little more RPM will help with that, as oil gets flung off the rod bearings, etc. faster.

 

[Nepidae]

First, I would suggest that for the definitive answers the only person to ask is Brian at American Diesel (https://americandieselcorp.com/). Brian is the ONLY expert on Ford Lehman engines.

Second, we have 2- 135 engines and I do my engine & engine room checks prior to starting the engines. I start the engines and move to the bridge, While I'm on the bridge the mate will make any last minute check and then will remove lines and I will have had the destination laid into our 8616 Garmin.

With word of the last line free, I back out of the slip and start forward on our course of the day. This is usually done at idle or a tad more. Clearing the marina I will bump it to 1500 and then after a few minutes and a clear path, I will move up to 1800 our cruising speed and engage the Follow Route on the MFD.

Both the engine and trans have dip sticks and the levels are marked on each. I'd adhere to those levels.

Treat these engines right, any questions ask Brian, he will take his time to answer your phone call, and they will outlast you.

Good luck.

 

[ronobrien]

Hello all. What is the average full warm up time on a 120 lehman. Ambient temp is about 70.

Now I'm not asking to the second. More like 8-10 minutes or about 15min or 5??

Also, on the velvet drive transmissions,, checking the fluid. Do you check that cold or warm? Engine running or off? I just did a completes service to it,,, fluid, cooler lines, and cooler. About a 1.5 quarts came out. I put in 1.75 to start. I figured the cooler and brand new lines (oversized per AD) being dry id add a touch more.

Thanks

Diesels don't need (or really want) much of a warm up. They like to work. Establish that you've got oil pressure and are making water out the back ( along with other pre-trip checks) and get underway. Keep the load light to moderate until the coolant temp is up to normal. It is also a good idea to run them hard periodically, (maybe 10 minutes at full throttle) after they have fully warmed up. Best time to run them hard is at the end of the days run. If they are turbo'd bring them back to idle for 5 minutes before shutdown. The turbos can run 100K RPM in some cases and you don't want to stop the oil flow until the turbo has had a chance to "spool down".

 

[Nomad Willy]

Diesels like to work .. indeed but after a rather lengthly warm-up.

Many posts here indicate the posters think the engine is warmed up when the coolant is at operating normal. Seems reasonable but engine parts don’t warm us as the coolant does. First of all the oil must be warmer than the coolant .. or the coolant wouldn’t get any warmer. Some engine parts are quite removed from the coolant and others very close. So It’s my opinion that operational warm up quite likely takes twice as long as coolant warmup.
Most trawlers are overpowered an w bigger engines longer warmup times should be the norm.. Like how long does it take to warm up your small outboard?
But it’s clear your not going to warm up your 4,000lb diesel very fast. And of course diesel engines don’t produce much heat till the start doing some significant work. Serious work is probably well past half load and way past half engine speed (rpm).

 

[rslifkin]

Diesels like to work .. indeed but after a rather lengthly warm-up.

Many posts here indicate the posters think the engine is warmed up when the coolant is at operating normal. Seems reasonable but engine parts don’t warm us as the coolant does. First of all the oil must be warmer than the coolant .. or the coolant wouldn’t get any warmer. Some engine parts are quite removed from the coolant and others very close. So It’s my opinion that operational warm up quite likely takes twice as long as coolant warmup.
Most trawlers are overpowered an w bigger engines longer warmup times should be the norm.. Like how long does it take to warm up your small outboard?
But it’s clear your not going to warm up your 4,000lb diesel very fast. And of course diesel engines don’t produce much heat till the start doing some significant work. Serious work is probably well past half load and way past half engine speed (rpm).

On most engines it definitely takes a few minutes after getting to full coolant temp to reach full oil temp. How hot the oil runs relative to coolant varies though. Depending on what the engine has for oil cooling and how much load it's under, I've seen engines where the oil runs 20 degrees cooler than the coolant and others where the oil is 40+ degrees hotter than the coolant.

 

[ronobrien]

Diesels like to work .. indeed but after a rather lengthly warm-up.

Many posts here indicate the posters think the engine is warmed up when the coolant is at operating normal. Seems reasonable but engine parts don’t warm us as the coolant does. First of all the oil must be warmer than the coolant .. or the coolant wouldn’t get any warmer. Some engine parts are quite removed from the coolant and others very close. So It’s my opinion that operational warm up quite likely takes twice as long as coolant warmup.
Most trawlers are overpowered an w bigger engines longer warmup times should be the norm.. Like how long does it take to warm up your small outboard?
But it’s clear your not going to warm up your 4,000lb diesel very fast. And of course diesel engines don’t produce much heat till the start doing some significant work. Serious work is probably well past half load and way past half engine speed (rpm).

You must have very large boat to have a 4000 lb diesel engine. The FL weigh in at about 1100 lb. The heat you speak of coming from the oil is from the cylinders at it's origin and the cooling jackets are placed specifically around the cylinder walls and cylinder heads for that reason. As you pointed out, most trawlers are overpowered for their cruising speed loading, so it is difficult to ever overload a trawler diesel. Given a proper design that would only be accomplished by changing to a much larger prop than the design was intended. To warm up a diesel just imagine you are going for a run. You don't stand outside waiting to warm up. You make sure your not injured in any way, stretch a little, then start a slow jog and increase your pace as you warm up. It's pretty much the same for a diesel.

 

[Orest]

Another important consideration if you tend to chug along just above idol on your final approach, run your engine at least 1800 RPMs for two or three minutes to clear the carbon out of your exhaust manifold and keep your engine happy when I first got my boat with the Lehman I used it for Fishing When I took my engine to have it rebuilt, the exhaust manifold was pretty much plugged so I was advised to do this procedure

 

[psneeld]

Another important consideration if you tend to chug along just above idol on your final approach, run your engine at least 1800 RPMs for two or three minutes to clear the carbon out of your exhaust manifold and keep your engine happy when I first got my boat with the Lehman I used it for Fishing When I took my engine to have it rebuilt, the exhaust manifold was pretty much plugged so I was advised to do this procedure

Not sure 2-3 minutes is near long enough at just a couple hundred more RPM than many run their Lehmans at will do much to clear the carbon.

 

[ronobrien]

Not sure 2-3 minutes is near long enough at just a couple hundred more RPM than many run their Lehmans at will do much to clear the carbon.

Truly the best advice is to run it under load at full throttle for 5-10 minutes while out. That will clear as much as your every going to get out otherwise. This approach has the added benefit of better sealing the rings to the cylinder walls.

 

[JMcJ]

A somewhat related question for other Lehman 120 operators. Our single has about 10,000 hours and has operated faultlessly in all that time. On startup, as the water temp increases at what I consider to be a normal rate, it creeps past 180 slowly to almost 200 on the gauge (original) and stays there for several minutes. Then it fairly quickly slides back to 180ish. As far as I can remember it has always done this. I have always (rightly or wrongly) attributed this to the water temp equilibrating after the thermostat opens. I did replace the thermostat many hours back with no change.

Have others observed the same behaviour?

BTW the heating coil for the domestic hot water tank Tee’s off the hose from the circulating pump in the common fashion.