Yanmar 6CXM-GTE Problem!

[Fast Forward]

These engines seem to have no compression. WHY!

Oil change, fuel filter change and winterized in the fall for the third year in a row. This spring out of nowhere both engines turn over sound identical and both seem to have no compression and will not start. I think this will be a major repair, but I hope not.
Coolant full, oil level normal, everything seems ok under the valve cover. Seems to have some backflow of air at the intake manifold while cranking.

Any thoughts woul be helpful.

[wissahickon]

First impression as long as you comtinue to have a backflow of air at the intake manifold you are lossing compression in one or more cylinders i.e. stuck intake, valve bent intake valve, bad valve timing. Curious same problem effecting both engines. A compression test will veryify your thoughts

[Fast Forward]

Mechanic was on boat today. Problem was carbon buildup not alowing the vaves to seat all of the way. Sprayed some cleaner in to break it up and get engine running. Some additional cleaning will follow.

[hubris 1]

Wrong oil? Incorrect valve adjustment? I thought about this all weekend. Now, Im no diesel mechanic but, it seemed like a fuel problem to me.
Think twice about that explanation he gave you. Your going to tell me a thousandth of carbon stopped the engine from firing? I dont believe it. I say, the racors ran dry back to the tank and the engine was fuel starved. Was it filled for the winter or as I suspect left half full? If what you say is correct, what your guy says makes no sense. Seapower....chime in.

[Fast Forward]

Hubris, I wouldn't belive it either, but...

I have done all work to this boat for three years. The owner called me and siad there was a problem when he went to start it. Engines sounded way different than they ever did before to me. Even with no fuel an engine sounds the same while cranking. The explanatin I recieved was from the owner who got it from the Yanmar tech that was on board. The one thing I care most about is that it was not my fault.

[seapower]

I didn't chime in for a reason. I don't like anything I've read yet. Certainly don't like the "fix". But I'm not there. I will say that the "carbon" build up didn't happen over the winter. There was a problem before the last shut down, spraying it with "snake oil" won't cure the problem. It may free up the valve's so that they will close for a start up. But until the "problem" (and there is a problem) is rectified, it'll fail again. Hopefully it won't fail in a catistrophic event. Frank

[hubris 1]

Seapower, I agree. I thought he may have drained fuel back to the tank over the winter and lost prime. If his issue is carbon he better fix it before he blows it up. Alot of times you get a warning if you pay attention to your engines and boat.
Its alot like having a dog........you just know when he doesnt feel right. He begins to behave a little different. Personally, and Im no diesel mechanic by trade I dont understand the explanation the mechanic did give. If it is accurate, and "truthful" to the owner he should be willing to find the cause.

[seapower]

Another member sometime back mentioned a "fix" that was done on his boat's engine, that put me in mind of what this member's "mechanic" suggested. He was talking about poor performance because of a fouled after cooler. The "fix" was to start the engine and spray a cleaner into the inlet side of the after cooler and clean it out. YOU"RE FIRED!!!!!!! Not only did ALL the garbage that obstructed the after coler go through the engine, but the cleaner did too!!! Just because it's not FLAMMABLE, doesn't mean it's not COMBUSTABLE. An engine is designed to run on a given amount of a known "fuel", Cleaner's, cold starting ether, solvent's,etc... lead to cracked ring's, piston crown's, bent rod's. Short cut's like the afore mentioned will lead to heart ache for sure. But hey guy's, keep on doing what you're doing. That's why the "good" tech's can't stay caught up. Frank

[Fast Forward]

I agree to all points. I don't do major engine repair and can't say what should be done. I have found out recently that the boat is never run up to normal cruise which could cause the carbon build up. I saw the invoice from the Yanmar shop, and it said CRC was sprayed through a plug in the air intake to free up valves on both engines to build compression. They also recommend a turbo wash and valve adjustment. I know CRC is no real fix but if they had used WD40 and duct tape I would say the job were complete.

[seapower]

That's kind of what I was thinking when I said to Alex that there was a problem before the last shut down. Alot of problem's folk's have with their engine's is operator induced. They need to run up in the range (cruising range) so that adequate boost pressure from the turbo will introduce enough oxygen into the cylinder's for complete fuel burn. This is not to say that they need to run at WOT either (some claim this). Most of the time you'll see the cruising range at 75 to 80%(normally) of rated RPM. It's also extremely important that they are able to turn up to rated RPM, this should be verified with a seperate digital tach. Frank