Yanmar 4LHA-DTE compresion test values

[tonci]

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!

 

[volvopaul]

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 .

 

[tonci]

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..?!

 

[tonci]

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

 

[BruceK]

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.

 

[volvopaul]

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 .

 

[lionelz]

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.

 

[tonci]

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.

 

[tonci]

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..

 

[tonci]

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!

 

[BruceK]

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.

:disgust: I'm not having a pop at you but what you propose to do is not the accepted way in going about buying a boat and just suggest you ask the owner if it's ok with them to dismantle his engine for these tests rather than take it for granted as being your right. And yes. FWIW I think 90% of the boaters here would agree with me, no tyre kicking spanner work from the punters please.

 

[volvopaul]

:disgust: I'm not having a pop at you but what you propose to do is not the accepted way in going about buying a boat and just suggest you ask the owner if it's ok with them to dismantle his engine for these tests rather than take it for granted as being your right. And yes. FWIW I think 90% of the boaters here would agree with me, no tyre kicking spanner work from the punters please.

I didn’t think this post would turn into such a debate .
Based on years of experience let’s go to the next stage .
If I was being employed as engineer to test the compression of this engine I would in the eyes and law of the vendor be responsible for any further problems to this engine borne from dismantling of the engine.
I will give you an example , some year back I acted as expert witness for a boat owner who had his engine removed and rebuilt by a company , the engine was never any good after the rebuild , it overheated, lost its coolant into the sump over a short period of time .
This was all from dismantling the engine which it turned out the engine didn’t require dismantling in the first place and it was a leaking exhaust elbow not the cylinder liner seals as first falsely diagnosed .

The point I’m making here is that further problems can occur , another example would be a tiny flake of paint after removing the injectors , paint inside the end of the injector pipe, then forced into the body of the injector damaging the nozzle , a result damaging the piston crown melting the piston because the injector has no spray pattern .
Or in the case of the yanmar engineer snapping a glow plug off in the head .

The buyer and seller here need to agree som ground on this , my point would be that if the engine doesn’t start well or under performs there could be grounds for investigation, but compression figures are pretty serious faults .

I for one will not carry out this test on any survey unless it’s proven there are issues with the engine.