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Old 09-01-2009, 22:20   #1
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Perkins 4.108 oil consumption

I have a Perkins 4.108 in my 37' yacht. It was recently fully rebuilt, including new rings and bearings(the pistons and liners were good), serviced cylinder head, pump and injectors(less than 100 hours ago). Prior to the rebuild it was being run on a 30 grade oil. Since the rebuild I have run it on Castrol RX Super 15W-40. It is overpropped and will rev out in gear to only about 2800 rpm. In neutral it will rev to 4000 rpm. It is burning a bit of oil, about 500ml in about 4 hours. Should I change back to a 30 grade oil, and run it on that until it has a few hundred hours on it. Or is it burning oil because it is overpropped.

I don't know whether it was burning oil before the rebuild, because I had only just recently bought the boat. I pulled the engine out and rebuilt it because it had a problem with the oil pump and would not pick up oil pressure after an oil and filter change.

Simon
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Old 09-01-2009, 23:06   #2
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My 4-108 burns about 1 quart in 25 hours...Sometimes more, sometimes less.

The variable seems to be how often I use the boat...If used often, say every day or every other day, it uses less oil. Easy to monitor as the oil is being spit out around the aft bearing and ends up on the blanket under the engine.

Also, if I top of the oil to the "max-mark" on the dip stick, it tend to use more, then the consumption stabilizes as the level gets half way down the the "normal" range. Could be that my dip-stick needs calibration due to the angle of mounting or what not. Moral of the story is that I don't bother to fill oil to the "max" any more, it will just be blown off.

You oil consumption may decrease or stabilize as the engine is being broken in.
Do you see blue smoke as in oil blow-by and un-seated piston rings?

Over-propping is not good: I had my prop re-pirched so as to achive 4000 RPM under full power underway. If memory serves right the current prop is about 10.5 X 16 or so...Had the prop-shop tweak it a couple of times to get it exactly right for the boat.

Have another prop that was too "coarse" and ended up with an over-prop situation: Nice and quiet it was with plenty of speed and low RPM..Instead it burned loads of fuel and over heated easy.

Now I settle on 70% of max continous RPM = 2100...It seems to be happy right there and the boat seem to be happy as well, not pushing hull speed and not too slow either, about 5.3 knots and 0.65 gallons per hour.

No sure if over-propping will cause an increase in oil consumption.
(For technical questions in the past, I have e-mailed Perkins in the UK and they were happy to reply and help out, try that..Give them your serial number and model number and they will look up production date, HP, etc.)

Good luck and lets know what shakes out.

PS..How much did ya pay for the overhaul and who did it?
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Old 10-01-2009, 00:01   #3
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Thanks.

I don't think I am leaking any oil. But I will try not topping the oil up to the full mark on the dipstick and see what happens.

But what grade of oil are you using.

I don't notice any oil smoke in the exhaust, but the boats does get black soot on the stern.

My boat makes about 5.5-6 knots at about 1800 rpm, and the engine temp is OK at that, But if I run it faster than that I don't gain much in speed, maybe another knot, but the temperature does rise a bit, so with the prop on it at the moment I tend to run it at about 1800.

The overhaul didn't really cost mush at all, because I have my own mechanical workshop. Engine parts, such as rings, bearings and gaskets are pretty cheap here in Australia. The big money was spent on getting the Borg warner velvet drive transmission rebuilt, and the heat exchangers and manifold rebuilt. I wish now that I gone to the trouble and expense of just putting a new Volvo or Yanmar in it. The old Perkins is just so noisy and prone to oil leaks.

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Originally Posted by CSY Man View Post
My 4-108 burns about 1 quart in 25 hours...Sometimes more, sometimes less.

The variable seems to be how often I use the boat...If used often, say every day or every other day, it uses less oil. Easy to monitor as the oil is being spit out around the aft bearing and ends up on the blanket under the engine.

Also, if I top of the oil to the "max-mark" on the dip stick, it tend to use more, then the consumption stabilizes as the level gets half way down the the "normal" range. Could be that my dip-stick needs calibration due to the angle of mounting or what not. Moral of the story is that I don't bother to fill oil to the "max" any more, it will just be blown off.

You oil consumption may decrease or stabilize as the engine is being broken in.
Do you see blue smoke as in oil blow-by and un-seated piston rings?

Over-propping is not good: I had my prop re-pirched so as to achive 4000 RPM under full power underway. If memory serves right the current prop is about 10.5 X 16 or so...Had the prop-shop tweak it a couple of times to get it exactly right for the boat.

Have another prop that was too "coarse" and ended up with an over-prop situation: Nice and quiet it was with plenty of speed and low RPM..Instead it burned loads of fuel and over heated easy.

Now I settle on 70% of max continous RPM = 2100...It seems to be happy right there and the boat seem to be happy as well, not pushing hull speed and not too slow either, about 5.3 knots and 0.65 gallons per hour.

No sure if over-propping will cause an increase in oil consumption.
(For technical questions in the past, I have e-mailed Perkins in the UK and they were happy to reply and help out, try that..Give them your serial number and model number and they will look up production date, HP, etc.)

Good luck and lets know what shakes out.

PS..How much did ya pay for the overhaul and who did it?
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Old 10-01-2009, 00:29   #4
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I use Shell Rotella 15-40, been pleased with the oil and have had it analyzed a couple of times, all with good results. It also keep the engine clean, no sludge, etc.

As for putting a new Volvo or Yanmar on the boat instead...Nah, save the money and buy premium beer instead of the Foster stuff ya blokes drink in Aussieland...

Your black smoke may go away when you get the prop issue sorted out.

As a measuring stick, with a correct sized prop you should be able to get 90% of full RPM with a wide open throttle in forward gear and tied to a dock.

Do a quick search on this here forum and you will find plenty of threads on the 'ol Perkins 4-108 and RPMs, prop sizes and all that.

I love my 4-108 and found it to be as reliable as a hammer, less so can be said about the Volvo's and Yanmars in my friend's boats, there is always expensive problems in them camps...

That being said, knock on wood: I am aware my 4-108 is now 30 years old and I try to hug it every day..Keep it happy you know.
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