I had the same occurrence

[Richard Dodson]

I had the same occurrence

I have a 2005 Sea Ray 390 MY, 6CTA 8.3 480. about 1300 hours. While running, starboard engine began running rough. Limped home on port eng. Found oil quantity had increased a bit. Pulled valve cover, #4 cylinder rocker shaft broken. Replaced, engine ran on all cylinders, however knocking was heard on top, in the vicinity of #4. After removing the head, it appears that the #4 exhaust valve seat failed. Best guess is that the knocking and rocker arm shaft failure was a result of the piston forcing the valve seat material against the head and valves. Looking at a 30K rebuild, head, pistons, sleeves and bearings. All will be done without pulling engine.

The engine# is: 46451379. I think there were more than one generation heads, the replacement part number that I have is 3936155. Am I correct, as the last thing I want is to have an old head with defective seats.
A year ago, I had the props refurbished to the 450 fuel curve, at 2100 RPM the smartcraft is indicating 26 GPH (total). WOT is 2600 with full fuel, water and 4 adults. Of course I have no idea how previous owners operated the

boat.

Any comments or suggestions would be appreciated.