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Old 10-12-2012, 12:00   #1
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Why my Perkins 4-108 was smoking

My 4-108 was smoking and leaving a sheen in the water of unburnt fuel. after checking injectors and injector pump it turned out to be a broken push rod and stuck valve. It was running on all 4 cylinders fairly well. unfortunately there is a lot of metal filings covering the rocker assembly. i have about 100 hour after a complete rebuild so it is disapointing news. I may change to a Yanmar 56hp but keep the Borg Warner gearbox to save some money.
Merry Xmas
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Old 10-12-2012, 12:25   #2
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Re: Why my Perkins 4-108 was smoking

Not sure why you should change. Beware, one possibility is that you got a little water in the cylinder (was it the aft cylinder by any chance?). When started up it bent/broke the pushrod. Had this happen on a 4-232.... and it seemed to run fine on 3 cyls too. Give some thought to your exhaust set up anyway I guess.... just in case.
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Old 31-05-2013, 17:11   #3
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Re: Why my Perkins 4-108 was smoking

I ended up renewing the 4-108. The valve that was stuck was the air intake. $4.5k later.
New head, new rings, 1 new piston, hone the bore and polished the crank. It is now running like a dream. No smoke and 185 degrees at 2,200rpm doing 6.75 knts.
$20k to replace with a Yanmar was a little to much.
Now all I need is time to sail.
Have a great summer everybody
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Old 03-06-2013, 10:52   #4
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Re: Why my Perkins 4-108 was smoking

So it seems that you had to take everything apart and re-asses the damage. How long did you run it with the broken rod? Did the complete re-build include the valve train? Goes to tell you...with diesels, exhaust smoke will tell you what you need to know.
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Old 03-06-2013, 11:48   #5
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Re: Why my Perkins 4-108 was smoking

As I had to service the injector pump because of leaking seals we thought that the smoke was coming from incorect timing. I ran the engine for awhile with a broken valve. Replaced the head with a redone one. Ran the engine on a 10 hour run this weekend with no problems (except a leak in the exhaust hose next to the mixing pot but that is another story). It seems to run a little hotter than before, 200 degs at 2,200 rpm. Before it was about 185 deg.
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