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Oil Loss through Crankcase Ventilation Tube

Doc Holliday

Well-known member
My next issue with the new (used) boat........

After taking the boat out four times, I've noticed that it seems to lose a lot of oil each trip. Like, maybe a quart or so every ten miles is my current estimate. There's no oil in the boat, but the rudders are covered, leading me to believe that it's coming out of the crankcase ventilation tube.

The engine's a 220 GPU. There are two ventilation tubes, one on the back of the crankcase, directly above the shaft it appears, and the other on the neck of the oil fill tube. It appears that the tube connected to the rear of the crankcase is the one that all the oil is coming from. There is also noticeble smoke (whispy, white smoke) that comes out of the rear tube. The exhaust does not smoke at all.

The engine runs strong, and if the runtime meter is to be believed, has over 530 hours on it. I run a six-blade warp drive, and the engine hits 2850+ rpm instantly. Oil pressure actually measures near 70 whenever the crankcase is full (10-12 quarts) and I'm running at around 2300 rpm, and settles down to around 50-55 after a while (probably after I've lost a quart or two of oil). I believe the oil pressure sensor is near the oil filter (front of the engine, on the accessory case).

My friend says it's probably my rings, and another guy I talked with said the engine may be gettin' worn out. I haven't measured compression yet on each cylinder, but will do that this week when I change the plugs.

Any ideas, other than buying stock in Shell?
 
Doc - No dealings with GPUs, but some of those Lycoming 540s do the same thing. Seem to hold 10 quarts, and quickly blow out anything over that level. With the smoke coming out of the tube, sounds like you have a ring problem at least. I would go with a compression check.

I know a friend with a 540 that ran 9-10 quarts in his motor for a few years. It wouldn't keep anymore than that, but then oil use stabilized and he could run 20 hours or more before having to add another quart. You might want to real carefully run the motor with just 10 quarts and see it oil use stabilized at 9 or 10 quarts and just operate the motor like that. But check oil use very carefully and make sure it doesn't keep slinging it.

Good Luck
 
You need to run an oil seperator when you have the crankcase vent on the rear. If you pulled the hose adapter out you would notice the crankshaft is directly below that and it has no obstruction to throwing the oil out from there. Most people I know just run the one breather on the fill neck with no problems, This is how my dad's GPU is set up and it throws no oil out the hose.

Larry
 
Is the same true for an 0540? Mine dosen't smoke from the exhaust but uses a lot of oil that seems to be coming from the hose used to ventilate the block.
 
Here's an article about the GPU engines from Airboat World Magazine. It has some info about the recommended oil level for those engines. Check it out.
http://www.airboatworld.com/newsmgm...icle_archive-detail.asp?articleid=78&zoneid=5

Also, my dad has the manuals for the 220, and it states that the recomendeed oil is straight 30 w. He's gonna start running that, instead of the high priced A.D. oil. Those engines stock have such low compression, that the Ashless components should not be needed. If I had one that was hot-rodded, I'd run the aircraft oil to help prevent pre-ignition, and pinging.
 
I've been told by quite a few airboaters that the 220 gpu when you get one that most burn or leak oil and if you get one that dose not burn oil that you got a good one but most say that every trip out that they burn a qt of oil and most of them are old timers. but i'm not an aircraft guy.
 
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