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Old 04-18-2015, 10:39 PM   #1
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How can you tell if you aren't firing on 1-cylinder?

Hi All,

I am a want-to-be trawler owner looking a 40' Tawain trawler (Aquacraft Boat Corporation - previously misidentified in a survey as an Aquastar). I did a sea trial today on this boat which has a Model 6D-380 Lehman. The boat started right up (though the owner had been there all morning so perhaps ran it earlier). I have known several diesels in my life (Kubota tractor, diesel in a sailboat, and several diesel vehicles) - but have never seen one without glow plugs - is this ever a problem for anyone in colder climates? The boat seemed to run well but I kept feeling what I would describe as what felt like a little 'miss' ... I thought higher RPM's might even it out and it might have a little- but I kept sort of wondering if it was possible that one cylinder wasn't firing. The Lehman does have very high hours (6500+- it has done several trips to Alaska, around Vancouver Island, and frequent trips to the Queen Charlottes).

I have hired a mechanic to come look at the diesel, but the person I hired who seemed to know diesels has hurt himself and is sending the person who works under him. Are there ways to confirm if all cylinders are firing - something I should make sure this mechanic does? There was nothing 'distinct' it just that sort of feel/sound thing that just felt like something wasn't quite right - but of course I had never met this diesel before. Any ideas appreciated as this is a big commitment and rebuilding an engine right away would be well beyond my budget

Thanks for any suggestions/thoughts!
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Old 04-18-2015, 10:51 PM   #2
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You can tell by cracking one injector line at a time while the engine is running at idle. If a cylinder is not firing you'll know it by whether it drops out as you crack the line.

Have some oil sorbs handy.
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Old 04-19-2015, 12:22 AM   #3
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Capt Bill is correct, a couple of wrenches and you can tell. It's messy.

What kills Lehmans is overheating. It's usually number 6 cylinder that gets pooched. First of all, they all smoke when cold. Lots. Once it's warm, black smoke usually means the injectors need overhaul. Blue smoke usually means its wearing out, burning some oil, or it could mean the dipsticks were never re-marked and it got overfilled. When you do your sea trial, run it WOT for 5 minutes. That will tell you if the no 6 is good, it will tell you if the cooling system, heat exchangers etc. are in good shape.

If the worst happens, Industrial Engines in Annacis Island rebuilds them, long or short blocks. Or, if you can overhaul a '56 Chev straight 6, you will have no problems with doing the Lehman yourself. All the parts are still available, cheap at the above or at a tractor shop.

If you think the engine is shot, make an offset in the price?

The Lehman doesn't need glow plugs - those are usually something to do with emission controls and the Lehman has none. There is a cold start "button" you can press for a cold start but I never needed to use it on mine. In Victoria, the sea never freezes so the engine will always be above freezing too.

The Lehman is arguably the best trawler engine of modest (120) horsepower ever made. It had a checkered career before we started floating them but it excelled at generation and such agricultural use as combines.

It should start promptly when cold, warm it up at 1000 rpm or even better, in gear. It will never reach operating temperature at an idle. Better yet, start it and throw off the lines and go. Then the neighbours won't get annoyed at the smoke! You should witness Grand Banks Rendezvous in Roche Harbour when 120 boats, some with twins, all start up on Sunday morning...
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Old 04-19-2015, 12:26 AM   #4
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Actually, a better answer would be to ask RT, there is some consensus here that he isn't. 8^)
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Old 04-19-2015, 10:49 AM   #5
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AD,
Along with cracking the injector lines one at a time (watch your tach to be sure the engine slows as each line is cracked and speeds up when tightened), I would also remove the oil filler cap on the valve cover while running and watch for steam/ base pressure rising out. I have 135 Lehmans and don't show anything. If one cylinder is not contributing, and you see base pressure/ steam- this could indicate low compression on that missing cylinder. IF that were the case, it could possibly be the result of overheating.


1983 Present 42 Sundeck
Twin Lehman 135's
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Old 04-19-2015, 11:14 AM   #6
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Greetings,
Mr. X. Keep it up pal. You'll soon be off my xmas list....And you don't wanna go there!

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Old 04-19-2015, 11:28 AM   #7
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Thanks RT, just dropping a bit of bait on your pond! Good day to you!
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Old 04-19-2015, 12:39 PM   #8
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I don't like the FL120 despite having had two of them for the last 17 years. But the absence of glow plugs is not an issue. They are provided with a cold start lever, on older boats like ours generally connected to a Teleflex cable and a pull knob on the instrument console. This disengages the limit stop in the fuel control in the injector pump and allows more fuel than normal to be fed to the injectors at startup. The instructions for using it are in the operator's manual. We have actually never used ours as it doesn't get that cold around here in the winter and we keep the engine room at 50 degrees or so during that time, so the engines start immediatey.

The typical quick way to determine if all cylinders are firing more or less correctly is to loosen (crack) each injector pipe coupling in turn while the engine is running. A change in engine sound and a slight drop in rpm indicates the cylinder is firing, no change indicates that it isn't. Make sure the engine surveyor does this.

It is said that the FL120 in typical recreational boat service is a 12,000 to 14,000 hour engine IF it is operated, serviced, and maintained properly during that time. I know of FL120s that have greatly exceeded those hours before needing a core overhaul and FL120s that didn't make it to 3,000 hours.
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Old 04-19-2015, 03:54 PM   #9
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Another not so precise way to determine if your not firing on one cylinder is with a spray bottle of water. Get the engine up to temp and spray a mist on the exhaust manifold where it comes out of the block going from cylinder to cylinder. If there's a cylinder not firing the water will not evaporate nearly as fast as a cylinder that is firing.
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Old 04-19-2015, 04:58 PM   #10
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Thanks all for your helpful information. I hadn't planned on going up for the mechanical inspection, but armed with this new information it might be helpful to be there and make sure the mechanic does all these things. I had asked about 'checking the oils' and he said that they can be sent to the lab, looking for metals and things, but without a baseline that it wasn't very useful information. So - I know he isn't planning on sampling it. There weren't a lot of mechanic choices unfortunately - and most specialized in outboards. At least this person is a diesel mechanic! I appreciate all the info!
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Old 04-19-2015, 05:35 PM   #11
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While your mechanic is correct in that oil samples are most valuable for showing trends, I think he's doing you a disservice by not taking one. A one-time or first-time oil analysis can be the start of sampling for trends and it can give you a snapshot of the oil's and tne engine's condition.

Our engine surveyor took samples from both engines and the generator. The results were very useful to us even though there were no previous samples on file to compare them to.
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Old 04-19-2015, 05:56 PM   #12
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A one time oil analysis can tell if there is antifreeze or salt water in the oil. Useful to know ;-).

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Old 04-20-2015, 07:57 AM   #13
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A quick way to check is with a laser temperature gauge. Check each exhaust at the head and if one of them is colder or hotter than the others then that one has an issue.
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Old 04-20-2015, 08:06 AM   #14
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Greetings,
Welcome aboard.
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Old 04-20-2015, 12:00 PM   #15
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Quote:
Originally Posted by wwestman View Post
A quick way to check is with a laser temperature gauge.
Exactly. You don't need any wrenches. You don't even need to touch the engine. Get one of these (I got mine on sale, and with a coupon, for less than $30)...
Non-Contact Infrared Thermometer With Laser Targeting

Shoot the exhaust manifold where it connects to each cylinder. If one is not firing, it will be significantly cooler than the others.

(And once you have this thing you will find dozens of other uses for it!)
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Old 04-20-2015, 12:02 PM   #16
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Another way to check (less messy) is to get a decent quality heat gauge and once the motor is up to temp, point the gauge at each injector individually. They should all read the same. Any cylinder that is not firing will be running at a much lower temp.
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Old 04-20-2015, 12:04 PM   #17
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To: DenverdOn....sorry, I posted my reply before I read yours. You're right, either the exhaust manifold or injector will give the same results.
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Old 04-20-2015, 01:00 PM   #18
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Quote:
Originally Posted by denverd0n View Post
Exactly. You don't need any wrenches. You don't even need to touch the engine. Get one of these (I got mine on sale, and with a coupon, for less than $30)...
Non-Contact Infrared Thermometer With Laser Targeting

Shoot the exhaust manifold where it connects to each cylinder. If one is not firing, it will be significantly cooler than the others.

(And once you have this thing you will find dozens of other uses for it!)

One of these is a fantastic investment, we bought one about 8 years ago and it's helped with more things then I can remember.
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Old 04-20-2015, 08:59 PM   #19
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If the exhaust is above the waterline, it's simple. Take a piece of paper and put it over the exhaust pipe. the skipping cylinder will pull the paper in the exhaust pipe. works on all engines, regardless of vessel. Water in exhaust makes it a little harder.

You can even use a dollar bill...

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Old 04-23-2015, 05:38 PM   #20
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Hi All,

Got a mechanical inspection and would be interested in opinions of this report. Doesn't seem bad for 6500 hours - but should I worry about more things in the near future.

This is what the report indicated:

Check over engine. It appears to be in fairly good shape. Was wet around top end, looks like V/C gasket leaking. Belts and hoses look good. Start up engine, check smoke (engine warm from owner running it earlier), a lot of smoke and appears to be blue in color. Check and record exhaust port temps: 1- 125, 2 - 122, 3- 124, 4- 141, 5- 127 6-145 degrees F. Coolant temp was 135 degrees F and RPM at 850, could not get RPM to go lower. Take boat out for a sea trial and ran up WOT RPM 2330 traveling at 8.6 knots. Coolant temp 186 degrees F, coolant started spraying out bottom of left hand side of exhaust manifold end cap. Dropped RPM and leak stopped, also rear cap has a wet spot on top of gaskets. Suggest resealing both, plus new thermostat and gasket on expansion tank and also replacing valve cover gasket. Noticed that it was wet at rear of head gasket though it may have been leaking - tasted liquid it did not taste like antifreeze, may be oil from V/C gasket. Tested 2 8D batteries #1 - 1247 Amp, #2 Battery - 1316 Amp, both batteries 1155 CCA, both tested good.

Following this the owner has replaced the blown gaskets and the valve cover gasket.

Thoughts? Does this seem pretty minor given the number of hours or would these sorts of issues suggest backing off the purchase or looking for a price reduction to cover future issues?? Apparently all cylinders were firing.

Thanks in advance for any thoughts!
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