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Old 02-17-2015, 02:07 PM   #1
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compression tester

Since I bought the boat a couple of years ago and started the refit, I've not devoted huge amounts of time to the engines , just regular maintenance.

It's time now to do a compression test on my 2715E Ford lehmans (120hp). Been looking on Amazon and ebay for a compression tester, but there's such a plethora of units available. Anybody bought any of these units and can attest that they have the correct adapters etc, and there functionality?
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Old 02-17-2015, 02:47 PM   #2
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Greetings,
Mr. MJ. I don't expect compression would have to be checked all that often. Would it not be more cost effective to hire a mechanic with the proper equipment and adapters to perform this task? PLUS, one more thing to store...
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Old 02-17-2015, 03:32 PM   #3
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compression kit

Hi Firefly.

Thought about that but while I pay 100-150 bucks for that service I could do it myself. And do the tappets at the same time etc. The boat is in the Caribbean as well , which leads to quality of available mechanics etc.

With serving my time as an engineer before becoming a boat builder the task is not daunting to me.

Just though somebody who is a Lehamn owner on the fprum might have already found a compatible kit.
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Old 02-17-2015, 03:52 PM   #4
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Martin:

The gurus on boatdiesel say that compression testing won't tell you much about the state of health of your engine. They say that diesels will show decent numbers even up until the end. Also a compression test requires removal of injectors and depending on the engine, replacement of crush washers.


A more useful test is blowby. All it takes is a connection to the crankcase vent, a proper sized orifice and a length of plastic tubing for a manometer.

I doubt if Lehman published blowby test criteria but Cummins gives blowby test procedures and new and rebuild blowby criteria. PM me with your email address and I will send you their procedure. It should be applicable to the Lehman as the Cummins 6B and the Lehman are about the same displacement. The newer designed engine is no doubt tighter when new, but I suspect that the rebuild values will be in the ball park.

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Old 02-18-2015, 07:31 AM   #5
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The simplest engine test is to observe the coolant temperature and smoke after engine start.

If the smoke clears up at a modest temp and short run time (UNDER LOAD) you have little to fear from the engine.

Next is use your ears , sounds goo it probably is.

Next is load test , run at full bore , pull back 10% in RPM and see if the boat keeps going and if the exhaust is clear.

Enjoy!
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Old 02-18-2015, 09:40 AM   #6
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Agreed...compression test isn't going to give you anything unless you're experiencing a problem. What will you do if the numbers are down, tear down the engine? Valve adjustment is a 1,000 hour interval (I think, don't have the manual here) maintenance item so do that if you're not sure when it was done. Hoses, heat exchanger cleaning, filters are the priorities unless you have a definite need to get into the engine.
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Old 02-18-2015, 09:49 AM   #7
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I agree no need to compression test. Simply crack open each injector line to see if that cylinder is working should there be some doubt. Blow by can be seen and felt at the crank case vent as well. The more likely problem with cylinders will be injectors going bad. With good fuel that almost never happens but with some junk or water it does.
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