Yanmar 6ly2a-stp 440 problems

Hi,

If fitting new Valves the Valve Seats can be generally be re cut to new specs and the valve lapping takes very little when everything is even and straight you do not need to replace them just because you are changing the valves.

Trying to lap a new valve onto a worn seat can be done if you are stuck and need to get it going but in most cases the lifespan of the seating area will be shorter than if it were done properly.

True, but I've found that when the valve seats are hammered by bad valves that are made by a bad material, it just shortens their lifespan. Either the bad valves are expanding a lot or losing their true shape as they heat up and the seats end up taking a beating. Also the seats can take a royal beating if the valve springs are weak and the motor is experiencing valve float.

In a case like this, I agree to replace the seats.
Not all valves and seats are made of the same material. If there was a poor decision on the metallurgy in the valves, who's to say a poor decision was not done on the seats. You will never be able to eyeball all seat damage.
Also, if your going to cut the seats, dome shape, stem height & spring pressure, may change just slightly. In a few more minutes, punch out the old seats and press in new ones. Small extra cost for a large investment.

Have 440 with approx. 350 hours, age 7 years. Problem is different, but wondering if it is related. Oil samples revealed copper in oil, 85ppm (Caution) at 300 hrs., 131ppm (Abnormal) at 350 hrs. Crankcase vent has some Blow-by (black smoke), and observed some reduction in oil pressure. Otherwise engine runs great, very smooth at both idle and running, no smoke, no overheating, etc. I do not see how this can be related to valve problems, but trying to figure out what is going on. Have had two knowledgeable mechanic/surveyors look at it. The only recommendation is to remove the engine and rebuild it. Seems like a bit extreme since there is no real diagnosis of the problem. With low hours, does not seem like a wear-out issue. Has anyone experienced this type problem? Is it a prelude to valve failure? Is there a single issue that can cause copper in oil, blow-by, and oil pressure reduction?

Not sure on this engine, fancy bronze valve guides are used in some engines.
Worn guides, case pressure. Humm.

Oil pressure reduction doesn't have a lot to do with a little blow by, nor valves usually. Bearing material is copper and I'd be looking at rod and crankshaft bearings, if you have low oil pressure.

CapnJack,

Copper in oil, damaged crank or other copper backed bearings.

Reduced Oil Pressure, damaged crank or other bearings reducing the resistance to flow thereby the pressure will be lower.

Blowby, scuffing of the rings/ liners caused by lower oil pressure not giving the correct volume of oil for piston cooling.

The choice is pretty simple, it does not read much link a valve problem, take you mechanics advice while you can salvage the major components , ignore it and look at a new crank and or block when it finally gives up the ghost.

I heard yanmar put out a service bulletin on this. Does anyone have a link to it?

I was the one who wrote the letter on behalf of San Juan Yachts, as I was the Service Manager and had dealt with two of our vessel owners who experienced not one but two engine failures, separated by 3 to 4 months.
This problem only affects the 440 hp version of that period, the failures were catastrophic in nature, no warning just “bang” and engine was dead. In all four of these engines,it was number 5 cylinder that melted down after a large piece of the Intake valve came loose. The block was typically ruined.
I found the Yanmar Service Bulletin which paid for the replacement of the valves. It applies only to Hinckley jet boats. I started with our Yanmar Distributor, and while San Juan had bought a lot of engines from them, it was no where near the volume of Hinkley. In short they said there was no problem and the sand pile is to your right- pound away.
After I sent the letter to the vessel owners that had the 440 hp engines, they would contact their Yanmar dealer, and were told that there was no bulletin on these engines in general, only Hinckley’s. When they would call me I could verbally tell them they whole story and advise them that their only safe course was to pay for a new valve job themselves, in fact I had the part number for the replacement valves and found out that Mack-Boring had a shelf of re-built heads all ready. I had a couple owners who got upset with me for informing them about this potential season ruining problem.
I then got a call from Yanmar America threatening me with legal action for espousing all the above- I told them “Bring it”, San Juan was extremely well represented and we would love to hear your answers in court.
There was an earlier post about a certain run of engine serial numbers that were suspect, could be true, maybe that is why there have not been more failures.

I’m looking to buy a 2006 Cruisers 46 Express with Yanmar 6LY2A-STP engines with 440 hours. What questions do I need to ask the dealer?

The service history of the engines would be a good start.

Read this whole thread. And be sure to see if the valves have been done

Lets look at it other ways;

Your looking at a problem child engine that is already 12 years old.
People now are nervous of it. When you sell her, what will the purchasing market think of it then?

354 cubic inch making 440 HP.
Notice dual staged oil filters. Coolers bolted on every where.
All kinds of stuff bolted on all over that engine to make more HP.
IMO, that is a high strung engine. Could be due for a rebuild now. Or when you sell her (see above).

Like the Cat 3116(26)s that went thru problems, personally I'd stay away from them also.

I've got no problems with old engines. The early problems my engines had were corrected before many of us were born.

I am in New England (RI) have a 2004 42 silverton convertable with these engines with just under 600 hrs port engine valve dropped, never had an issue and maintained to specs insurance got involved and surveyor after all inspection and valves sent out for metal analysis concluded defective valves engine serial # port 52517 starbord 52514 how do I petition Yanmar insurance covered 50% due to depreciation on port engine I am having starbord engine head replaced $8K. any help greatly apreciated

Do

Don’t waste your time with Yanmar America. Sorry about your insurance policy using ‘depreciation’ to reduce their exposure. Guessing it is a BOAT/US policy?

Your not going to get squab from Yanmar America.
Just remember this exercise and expense on your next boat purchase.

I am looking to buy a 2003 Stamas with twin 440hp Yanmars. The current owner bought it 4 yrs ago with 1100 hrs and has put on another 700hrs , 1800hrs total. I like the boat but after reading the thread worried about these engines. Can i assume with 1800hrs and running strong, that these particular engines are out of the "problem window" and maybe go on to get a couple thousand more hrs? Has any body heard of the Yanmars going 3-5 thousand hrs?

I see you never got a response. I can add some info I learned over the summer. Maybe it will help you or others.

I chartered a 50' boat through Moorings in the BVI. The checkout captain worked on/in/around BVI charter boats his entire life...his dad was a charter captain in the BVI as well and he was a deck hand at 12.

The issue of Yanmar engines came up as we ran the boat at high rpm across the channel. He replied by stating they have several hundred boats at any time in their fleet, mostly less than 5 years old, almost all with Yanmar. They accumulate thousands of hours on each boat over their time at Moorings. The boats are often run hard, many times by users that don't care about maximizing the life of the engines. He said they have proven to be the best and most reliable, trouble free engines, that is why they are used so heavily in charter by Moorings and many others. He said they have proven to be very durable. Moorings keep up with the service intervals, and they expect the engines to just run...and they do. He said Moorings had a short period where they used John Deere on some of the power cats. He said they just did not hold up as well as Yanmars to the high hours, high rpm, charter abuse and they phased them out quickly. He said of all the diesels he has run, he has become a true believer in Yanmars. He is just just one point of reference but I would say he comes from a very knowledgeable perspective and sees boats get used (and abused) on a scale that most yachts would never experience.

The thread refers to some engines built quite some time ago, so maybe the problems are resolved.

Charter service usually does not use high strung - high HP engines.
Yes, the lower HP engines can run a very long time.

Sorry I did not see post #58 or I would have repeated my self from post #53.
Now others think the Cat issues have been resolved, That is a poor poker hand.

OTOH, Maybe, Maybe, Maybe the head and other issues were fixed under the original owner.
You good blind mans poker?

If you really, really like the boat, Survey the heck out of those engines. Ask for all oil lab work and keep your oil labs up.