F250 Yamahas "making oil?"

[petrel]

I purchased my boat used. The engine surveyor noted that the engine oil was an inch high on each dipstick. The engine surveyor, also a yamaha dealer, called it "making oil" and simply drained off the excess and blessed my purchase. I ran the issue by my local dealer and he said that it was caused by idling the boat excessively, which allowed fuel to enter the oil. When we checked the engine log, that seemed to fit.

When I got the boat home, I had the dealer change the oil and filter. The oil level did not change for 70 hours. I changed the oil again this spring and only filled the oil to within 1/2" of full. After about 10 hours of use, there was no change in the oil level.

I just had the whole fuel system overhauled for a fuel problem (see purging f250 fuel system). So, after the repairs I took a week off and rant the pizz out of the boat. After 225 gallons of fuel, the port engine reads 1" above full on the dipstick, the starboard reads 1 3/4" above full!

I flounder fished three of the days, which was a lot of drifting and idling, but the rest of the time we were bumping along at 5000-5400 RPM. Is this just "making oil" and the stuff will evaporate, or a sign of a more serious problem?

[Mickey]

When I got the boat home, I had the dealer change the oil and filter. The oil level did not change for 70 hours. I changed the oil again this spring and only filled the oil to within 1/2" of full. After about 10 hours of use, there was no change in the oil level.

Make sure you're measuring the oil with the engine in the same state each time - I'd suggest vertical for 30 minutes after shutdown - not tilted.

I have F225s and have never seen this problem. Adulterated oil could be a lubrication issue - if, for example, you have a water jacket leak and seawater is raising the level or gasoline could cause a oil film breakdown on a friction surface, like, say, a main bearing.

I'd do this:

Drain the oil into a non-opaque container - if you can find something glass that will hold 6.x quarts, more the better. Replace the oil filter and cut the old one open (yes, it is a mess) and look in the pleats for anything that doesn't look like filter or oil. Dispose of the mess responsibly, please!

Allow it to sit 24 hours. Look for separation at the bottom or at the top. Bottom, likely water, top, likely gas.

Whether or not you see anything, mix it thoroughly and send a sample out for analysis. It may be the best $30 you'll spend.

It is not normal for oil levels to go up, only down. Engines don't "make oil" and if your oil volume increases it is coming from somewhere.

Note - I am not a Yamaha mechanic, there may be a better explanation, but as an owner with 400+ hours on a pair and 30+ years boating, this would be a serious concern to me.

Mickey

[wilde1j]

Leaking injector(s) may be the cause of fuel getting into the crankcase after shutdown. If oil smells like gas, have a dealer do leakdown tests on the injectors.

Edited August 17, 2009 by WildeOne

[Mildog]

I have heard of this issue on striper fishing forums. Guys trolling at idle speed all day..with yamahas. I have not heard of any official replies from yamaha stating the cause or prevention. I did see a few replies to simply make sure you run the motor at higher rpm for 15-30 minutes and the gas in the oil would burn off.

[petrel]

I had heard and read so much on the topic that I decided to get it straight form the horses mouth. Called Yamaha customer service today and asked him about the problem, just as I described it in my initial post.

The representative stated that it should not be allowed to happen and should be addressed immediately. He stated that it was most common in engines that were not broken in properly, but that it could be from: Rings not floating (possibley caused by improper breakin), stuck thermostats, over propping, open pressure control valve.

He went on to say that the previously mentioned Leak Down test would probably indicate improperly seated rings due to carbon buildup. If this was the case, and he was almost certain it was, he recommended a "shock" treatment of ring free, followed by another Leak Down test. If the engines failed another LD test, the engine should be treated with Yamaha "engine cleaner."

The representative was very casual about this and went on to say that he was relatively certain that this would take care of the problem. I pressed the issue that it should be covered under warranty because it was so prevalent. He said that they did not cover it because they could not monitor how an engine was broken in or operated.

I asked him how to operate the engine. He said that the engine must be brought up to "operating temperature" at every use. I asked him if that was the notch on the gauge past the middle and he said that should do it if the thermostats were not stuck and the pressure control valve was functioning normally.

I told him that my engines did not really heat up until I ran them a while over 5000 RPM, but that I preferred not to run it hard all the time. He said that I could run them at WOT for it's entire duty cycle without any ill effect, in fact, it would be better for them!

I'm off for a Leak Down test in a day or two. Wish me luck!

[HOTSPOT]

In 1300 hours with my F200, 90% were below 1000 rpms. Never made oil, never.

What the Yamaha guy said makes perfect sense to me.

These four strokes are made to run, but most folks just don't run'em. You'll do more damage babying them than you will rawhiding them.

[petrel]

My dealer says that they will pump the ring free directly into each piston, let them soak overnight, then blow them out with compressed air and leak down test them again. Not exactly what Yamaha recommended, but I guess they know what they are doing?

Looks like the whole thing will have to wait a while though, just slipped the tranny on my F350 while hauling a utility trailer with a tractor on it. Waiting to get that fixed before I can drag the stinkin boat in for repair.

[HOTSPOT]

Nothing wrong with what the dealer is saying. That is an "old school" trick that may help free up a stuck ring.

[petrel]

I guess it would be preferable over installing an auxillary fuel tank and running a shock treatment through the engines? Of course if the engine passes the leak down test, I'm looking at thermostats or pressure control valves. Wouldn't you say that it would be unlikely for those to malfunction simultaneously in a twin engine setup?

[HOTSPOT]

Yes, very unlikely.

Back in the day, on the farm, we would pour diesel fuel into the cylinders of our gas burning tractors after they had sat over the winter. Pour it in and let it sit for an hour or so, then spin the engine over with the plugs out, then change the oil, put the plugs back in and fire them up for the spring. Those tractors still have good compression and still break land every spring.