Cummins Marine Diesel Repower Specialists › Forums › All Other Marine Diesels › Yanmar 6ly2 STE 420
Rob Schepis.
I am
Looking at formula 40 Pc with this engine set up yanmar 420 about 500 hours ? The valve issue I have been reading about fall with in these motors what is the fix? I know you need get wot up til 3400 what are the issue beside not rebuild able is it recommended to stay clear these models thanks
There is only one serial number “issue” for the 6LY2(A) that I am familiar with. Serial # M56928 circa 2005 when the heads on the 6LY2A were improved using inconel valves. But that’s when they were calling it the 440, no longer the 420. Your serial number is way earlier than that head upgrade era. A remanufactured head should be available with the Inconel valves. You would have to contact Mack Boring or Mastry to check on availability.
Maybe you are getting confused with the exhaust valve seal issue on the smaller Yanmar, the 6LP, (300/315hp) and that was in the very late 90’s early 2,000’s but different issue, different engine.
Generally speaking the 6LY2A is not an easy engine to work on. The raw water pump is challenging, the seawater side is complex and getting old. Replacement coolers are pricey and not sure if parts sourcing is becoming difficult. Another thing to check with the distributors about. The engine is also coolant sensitive and very sensitive to overloading.
I would probably have accepted one of these engines very early in it’s life but the “older” they get the risk increases. Has she been overloaded since day one? Has the seawater side been maintained? Has the proper coolant and change out intervals been adhered too?
3,400 is not quit there as to prop loading. See attached. If there was ever an engine you need to prop light and run light this is the one.
Your concern is definitely a valid one, especially in a boat like that which is normally run by someone who is looking to get from A to B in a hurry.
You must be logged in to reply to this topic.