671N leaking oil

"I have a pair of inline 6-71&

"I have a pair of inline 6-71's in a 42' shrimp boat. Engines are very old (1978 vintage) with in excess of 8000 hrs on each. Starboard engine recently suddenly started leaking/blowing excessive amounts of oil into bilge (2+ gallons in 10hrs run time) but I can't tell where it is coming from. Blow by tubes are both clogged and nothing is coming out of them - would this cause engine to blow oil from other areas? Also, port engine has always blown white smoke on startup but does not appear to be burning much oil. What is likely cause of white smoke? I know it is probably time for overhaul, but am trying to get through the end of the season before tearing them down. How many hours are possible to get out of a 6-71N in these low rpm commercial set-ups? I've heard others getting 10-12,000 hours. Thanks."

Hi I am having the same problem with my 6-71 DD. Did you get through with your problem I cant seem to find where the oil is coming from. I made a 6 hour trip an lost approximately 4 gals. of oil on my starboard engine.

Blow by tubes ?are you saying 1/8 inch tubes, if so these are air box tubes and yes this will cause oil to blow out gsks.if white smoke go away after worm up then it caused from cold stuck rings, when worm they come unstuck.10 to 12 with care and good maints

Check Your Blower on the side of the bock it may be the seals have gone bad they do from time to time 8000 hrs is a lot of hours. I used to be an engineman in the Coast Guard and have worked on a lot of 6-71 series eng.
Reguards Fred Durbin
[email protected]