Yanmar 6LP-STE Valves

a_braley · Jun 14, 2024

I am looking at a boat with a 1998/99 Yanmar 6LP-STE engine. Records show that the boat was sold in 2016. During the sale records indicate that two injectors were rebuilt by the seller and a compression check was paid for by the buyer. A couple months later the seller paid for the head to be removed and machined. During the work on the head the invoice indicates that only two exhaust valve stem seals were replaced along with the lock springs and other disposable seals and gaskets. Total cost for the head work was $6,600 (Cnd$). I am not a mechanic but find it unusual that they would go through all the expense of pulling the head and not replace all of the $19 seals and maybe even the guides.

Is this normal during what I am guessing might have been the replacement of a blown head gasket. Maybe it is better to not mess with the valve guides and seals if there appears to be nothing wrong with them (if it is not broke don't fix it)

lwarden · Jun 14, 2024

How many hours on the engines?
These are generally considered good engines, but that engine and year may have been subject to some valve seal issues along with the mentioned valve lock spring. The update to the lock spring was to prevent a catastrophic valve drop occurrence. I'm not sure if this year falls in the category of affected engines. As you said, I would be surprised if they didn't do all the seals while they were in there and yes it seems odd.

DavidM · Jun 14, 2024

More concerning is why was the head milled. Maybe an overheating incident that warped the head. What caused the overheating.

Also sounds like a lot of money for what was done. Makes you wonder.

David

a_braley · Jun 14, 2024

At the time of the work there were 1,750 hours. Eight years later there are now 2,100 hours (lots of sitting).

KnotYet · Jun 14, 2024

I have no direct knowledge of this engine but normal practice for machining a head
would be to remove all 12 valves and hot tank it first if there was any corrosion.
To only replace 2 exhaust valve seals may indicate that only 2 cylinders were
impacted by the event that required the head work. Volvo parts prices or supply
issues may be why the other 10 seals were deemed acceptable to re-install.

ofer · Jun 14, 2024

just wanted to add that that original engine had valve issues right from the get go. Yanmar offered to re do all valves etc. under warranty for a few years after the occurrence. it might be worth to find out if your engine was one of them.

GLee · Jun 28, 2024

a_braley said:
I am looking at a boat with a 1998/99 Yanmar 6LP-STE engine. Records show that the boat was sold in 2016. During the sale records indicate that two injectors were rebuilt by the seller and a compression check was paid for by the buyer. A couple months later the seller paid for the head to be removed and machined. During the work on the head the invoice indicates that only two exhaust valve stem seals were replaced along with the lock springs and other disposable seals and gaskets. Total cost for the head work was $6,600 (Cnd$). I am not a mechanic but find it unusual that they would go through all the expense of pulling the head and not replace all of the $19 seals and maybe even the guides.

Is this normal during what I am guessing might have been the replacement of a blown head gasket. Maybe it is better to not mess with the valve guides and seals if there appears to be nothing wrong with them (if it is not broke don't fix it)

Yanmar (like all engine manufactures at the time) was dealing with emissions issues on the 6LP-STE. The original seals were "too good" and impeded valve guide to valve lubrication. There were many valve failures, some of which caused catastrophic damage. Yanmar revised the seal (I believe the updated seals have a blue color code) and all was right in the world once again. It sounds strange that only 2 were replaced. So strange that I'd question if that was indeed the case.
There is extensive discussion on this issue at Boatdiesel.com. If you're serious about the boat and want to know more, the membership would be well worth the minimal cost.
Greg Lee
No connection or affiliation with Boatdiesel.com (just a long standing member)

KnotYet · Jun 28, 2024

KnotYet said:
... Volvo parts prices or supply issues may be why the other 10 seals were deemed acceptable to re-install.

Oops, I just noticed this error in my earlier post. I meant to write 'Yanmar'.

Yanmar 6LP-STE Valves

a_braley

Member

lwarden

Guru

DavidM

Valued Technical Contributor

a_braley

Member

KnotYet

Guru

ofer

Guru

GLee

Member

KnotYet

Guru

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