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  1. #1
    Join Date
    Feb 2019
    Posts
    13

    Default Yanmar 4LHA-DTE compresion test values

    Hello to everyone!

    In two days time, i'll be heading to check out a used boat, (starfisher 780) with this Yanmar engine.

    I can't seem to find, anywhere, compression-pressure values...

    If anyone knows and is willing to share, factory and minimum pressures, for this engine I would be gratefull !!

    Any other advice for this engine/boat is also welcome..

    Thank you very much!

  2. #2
    Join Date
    Apr 2007
    Location
    midlands
    Posts
    7,346

    Default Re: Yanmar 4LHA-DTE compresion test values

    Unless there is an issue with the engine why would you want to carry out a compression test ?
    Carry out your sea trial , as long as it starts easy from cold there should be no problem, this engine is a very reliable unit .
    If you do carry out the test the figures need to be within 30/40 psi of each other .

  3. #3
    Join Date
    Feb 2019
    Posts
    13

    Default Re: Yanmar 4LHA-DTE compresion test values

    Quote Originally Posted by volvopaul View Post
    Unless there is an issue with the engine why would you want to carry out a compression test ?
    Carry out your sea trial , as long as it starts easy from cold there should be no problem, this engine is a very reliable unit .
    If you do carry out the test the figures need to be within 30/40 psi of each other .
    Thank you for your answer!
    I think a question would be.., why not, carry out the test?! Is there a reason not to?
    It's pretty simple to do it, on that specific engine. The whole process doesn't take more than 30 min. I have a tester and knowlege, how to do it.
    Why not have, the exact numbers?

    A am aware that the difference betwen cylinders is more important than the value itself, but I would really like to know, values of the new engine and the minimun pressure allowed. That's information i was not able to find anywhere..?!

  4. #4
    Join Date
    Feb 2019
    Posts
    13

    Default Re: Yanmar 4LHA-DTE compresion test values

    One more thing...

    Let's suppose for a moment, that the minimum pressure alowed, is 24 bar. And the test shows close to that number.., 25, 26... I am sure that the engine will still start with no problem, especially since it is still pretty warm outside.

    But in that case, the seller will certainly not recive the amount of money, he is asking for the boat

  5. #5
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,203

    Default Re: Yanmar 4LHA-DTE compresion test values

    If some prospective buyer came to my boat with a pressure tester I'd tell him very quickly where to get off and go home. If he wants to pay for yard work and certified engineer to do the test and return the boat to condition that's another thing entirely. Be prepared to be disappointed and your trip wasted unless you have the owners blessing for you to start dismantling his engine before setting out. It's not as painless or risk free as doing a test on a petrol engine where you just whip out a sparkplug.

  6. #6
    Join Date
    Apr 2007
    Location
    midlands
    Posts
    7,346

    Default Re: Yanmar 4LHA-DTE compresion test values

    The correct way to check how healthy an engine is to carry out a cylinder leakage test not a compression test , they are totally different tests . Over the last 39 years I’ve only carried out compression tests on engines with faults to determine if it which cylinder is at fault or to find a leaking head gasket or a gasket that’s failed between the next cylinder.
    I run a couple of Historical Ford Cosworth BDA engines , my builder carried out the leakage test to one that was slightly under powered , the power was lost through a very slightly sticking valve , now I did my own compression test which all 4 cylinders gave the same psi reading , the leakage test was the only way to determine what was wrong , the fault was down to a broken valve spring .
    For what it’s worth to you I’d be looking at 350 to 400 psi .

  7. #7
    Join Date
    Oct 2014
    Location
    Gosport
    Posts
    436

    Default Re: Yanmar 4LHA-DTE compresion test values

    FWIW I have one of these engines fitted in my boat only difference mine has a sterndrive fitted. Mine is the 240 version and I have to say it performs as per the data sheet. I would recommend that engine to anyone.

  8. #8
    Join Date
    Feb 2019
    Posts
    13

    Default Re: Yanmar 4LHA-DTE compresion test values

    Quote Originally Posted by BruceK View Post
    If some prospective buyer came to my boat with a pressure tester I'd tell him very quickly where to get off and go home. If he wants to pay for yard work and certified engineer to do the test and return the boat to condition that's another thing entirely. Be prepared to be disappointed and your trip wasted unless you have the owners blessing for you to start dismantling his engine before setting out. It's not as painless or risk free as doing a test on a petrol engine where you just whip out a sparkplug.
    Well, what can I say.., when some prospective buyer comes to your boat, you do that.
    You don't know anything about arangement between seller and myself.
    And why would my trip be wasted? I'm looking forward to see the boat and take it for a ride! Enough for my trip, not to be wasted.

  9. #9
    Join Date
    Feb 2019
    Posts
    13

    Default Re: Yanmar 4LHA-DTE compresion test values

    Quote Originally Posted by volvopaul View Post
    The correct way to check how healthy an engine is to carry out a cylinder leakage test not a compression test , they are totally different tests . Over the last 39 years I’ve only carried out compression tests on engines with faults to determine if it which cylinder is at fault or to find a leaking head gasket or a gasket that’s failed between the next cylinder.
    I run a couple of Historical Ford Cosworth BDA engines , my builder carried out the leakage test to one that was slightly under powered , the power was lost through a very slightly sticking valve , now I did my own compression test which all 4 cylinders gave the same psi reading , the leakage test was the only way to determine what was wrong , the fault was down to a broken valve spring .
    For what it’s worth to you I’d be looking at 350 to 400 psi .
    Thank you for bringing it to my knowlege! Certainly useful info..

  10. #10
    Join Date
    Feb 2019
    Posts
    13

    Default Re: Yanmar 4LHA-DTE compresion test values

    Quote Originally Posted by lionelz View Post
    FWIW I have one of these engines fitted in my boat only difference mine has a sterndrive fitted. Mine is the 240 version and I have to say it performs as per the data sheet. I would recommend that engine to anyone.
    Thank you very much! I am happy to hear that!

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