Author | Theme: 4-Stroke Engines: "Oil Making" |
Jim | ![]() The term refers to the situation where the oil level in the lubricating oil sump rises over time as a result of contamination with gasoline that has leaked from the piston rings of the cylinders. It appears that this problem is most evident on a new engine during the break-in period and on engines running at low temperatures, preventing the contaminated oil from boiling the gasoline. Was this an issue on any of the 4 strokes belonging to our Whaler audience? |
fat fish | ![]() You will smell the gas if you are in the oil smelling the dipstick. In order for the gas to pass through the rings, a few things need to happen. First, the rings are worn, but usually this will cause it to smoke. Second, a (leaking) carburetor or injector is bad, causing the cylinders to fill with gasoline when the engine is turned off and slowly passing through the rings over time. Rings are designed to contain oil, not gas. If the engine is started while this gas is in the cylinders, the compression could cause the rings to break on start up. Or a bad intake manifold gasket, etc. Gasoline entering the crankcase doesn't just "happen". |
TOM | ![]() After reading this post last night, I wrote to one of my friends who practices in Alaska. Your welded aluminum fishing boat is powered by a 75 HP 4-stroke Mercury engine. Because he uses the boat for both business (traveling to see patients in his locum tenens settlement) and leisure (fishing and tourism), he has logged over 300 hours on the engine in just over a year. He reports NO [emphasis his] engine problems. He says he will be contacting the owner of some of the local fishing lodges, all of which are converting or have been converted to four-stroke engines. Has a similar situation been described with four-stroke automobile or aircraft engines operating in cold climates? Would this situation be unique to gasoline engines, or would diesel engines be affected as well? My technical knowledge in this field is limited, but it seems that only a malfunction would create the situation you describe. PM |
weekend warrior | ![]() |
dgp | ![]() Many factors come into play here; oil level at drain interval, oil mark, fuel consumed, operating hours and engine angle during check. You are definitely not trolling here! |
TOM | ![]() dgp raises an interesting point. Lhg got you into this? IT'S A JOKE! Your recent posts seem to be critical of the horsepower of four-stroke engines and clearly express your loyalty to the Mercury brand. PM |
Jim | ![]() On the Yamaha/Mercury angle, I found it amusing that the original complaint I read about this referred to the engine as a Mercury 4-stroke. But the problem is in the head. When people talk about how good their Mercury 4-stroke engine is, "Oh yeah, but that's a Yamaha engine" always comes up. So when there's a problem, he goes back to being a "Merc". From the results seen so far, it does not appear that this is a widespread problem. Honda outboards were also mentioned in this context. The usual solution suggested by dealers is to change the thermostat to a higher temperature, causing the engine to run hotter. I find it helps to boil water or fuel in the lube oil reservoir. Another review I read mentions changing the crankcase oil more often, every 50 hours. I think some people really enjoy working on their engines. |
suburban boy | ![]() sub |
gss036 | ![]() Yamaha has a really serious gas-in-oil problem on the previous model (89-90) 9.9 hp high thrust 4-stroke. I've had 3 or 4 friends who have received changes when theirs stuck due to high gas content in the oil. I change my oil every 25-30 hours just in case, $1.29 for a quart of oil every month is cheap insurance for a $2800.00 engine. |
capital | ![]() |
PECESNFF | ![]() I think you spoke to the WHO people. I personally know a gut with a twin 90 (2001) in an outrage 22 with this problem, and another with a twin 75 (2000) in an outrage 21 1970. Both were taken care of under warranty. They were less than 2 years old but had almost 1000 hours on them so Merc must know they have a problem. If I remember correctly, they said it was water in the crankcase, not gasoline. The transoms of these two boats sit low in the water and both drag slowly or drift. I only have a few hundred hours on my 90, and mine seems to burn a little oil, not gain. I get blue smoke on startup or after sitting in water for a while. The dealership said this is normal. PECESNFF |
PFSQUAN | ![]() I'm not sure if you mean a 12V71 turbo, but in any case if fuel gets into the lube oil you have a problem. |
capital | ![]() |
TOM | ![]() PM |
capital | ![]() |
doctor t | ![]() |
sal dimercurio | ![]() Thanks. Sal |
Jim | ![]() The current thread here contains more information than what I first read. |
David Jenkins | ![]() |
blue corridor | ![]() http://thehulltruth.com/6/ubb.x?a=tpc&s=382602711&f=436600231&m=8676024683 http://www.walleyecentral.com/dc/dcboard.php?az=show_topic&forum=6&topic_id=125752&mode=full y http://www.boatsetup.com/cgi-bin/ubb/noncgi/ultimatebb.php?ubb=get_topic;f=7;t=000732#000000 |
Clark Roberts | ![]() |
jws | ![]() The engine produced oil when it was briefly out of warranty. The local dealer I bought it from claimed to be completely unaware of the problem. I removed the intake manifold with all three carbs and checked everything. The engine continues to produce oil. Then I replaced the fuel pump. $80 or more. Problem solved. Earlier this year, on another forum, I found a thread about how to produce oil. Poster had the same engine with the same problem as mine with the same cure. I advise an oil analysis if you have a 4 stroke and are in doubt. I also have a Detroit 4-53 powerboat. Sturdy little motor that will make your jaw drop if you don't have great soundproofing. Fun to work with, simple, reliable, cheap to operate and parts. "Runaway" stories are some of the best. |
jws | ![]() I apologize to the moderator. You may need a new strand in two strokes running backwards. |
mrpike17 | ![]() |
Jim | ![]() If you have a question about four-strokes that "make oil", start a new discussion. Thanks. [Topic closed.] |
4-Stroke Engines: "Oil Manufacturing" - Moderated Discussion Areas (2023)
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