Yamaha T8 making oil

About a year and a half ago I bought a like new 2002 T8, it runs perfect, works great but makes oil. I try to run it wide open each trip for a little while but that does not seem to change things. It makes enough oil that after a couple uses its out of the normal range on the dipstick. It uses less than a quart of oil so I have just been dropping the oil a couple a times a season, but was wondering if there is a hotter thermostat I could try or anything else to help with this. Thanks.

Have you replaced the thermostat at all? Mine got week about a year or 2 ago and was stuck in the open position. I was not only making oil but it was looking milky due to condensation. Take your current thermostat out and see if it is open or closed.

Please explain to me how an engine can “make oil”. If the oil level is increasing while the engine is running, something is leaking into the crankcase. The foreign substance leaking into the crankcase can only be two things, either water or fuel or both.

Lubricating oil that has been diluted with either water or fuel needs to be drained completely and replaced. The source of the leakage needs to be determined and corrected.

Fuel can leak due to a faulty diaphragm. Water can leak due to a faulty gasket.

Have you installed a fuel demand valve? Do you have one of the epa fuel caps and a tank that swells up like a balloon in the heat?

First off, its not making oil. It is diluting you oil with either water or fuel.
Both are bad.
First you need to determine if it is fuel or water.
Drain your oil onto a glass container, let it separator for a few days and you will see the layering. Using a seringue suck the top layer off squirt it in a metal tray and see if it burns.

What type of tank do you use as the fuel source for the kicker?

1. Add a fuel shut off to the kicker. This will make sure that fuel pressure is not being put to the kicker if it plumbed incorrectly. Could also be a bad carb needle valve or fuel pump issue if it uses crank case pressure to operate.

2. Could be a head gasket leaking or cracked cylinder even.

Yes I realize that it not making oil, its fuel that is getting in the crankcase, its a commonly used term for this problem. Often this is caused by the engine not getting warm enough to burn it off thats why I asked about the thermostat. I know some other engines that have had this problem have been fixed by using a themrostat that runs a little warmer. It is in a Ranger boat with a seperate kicker line from the main tanked, plumbed in at the factory. I have not removed the thermostat yet, will get to it this week. Oil is not milky, it does smell like gas, I unhook the gas line when not in use and drain the carb when not using for more than 2 weeks. Thanks.

Process of elimination but stuck open needle would be my first guess. Stupid question are you running the correct plugs?

There have been a number of four stroke outboards with this issue. It is usually tracked down to a bad thermostat engines runs too cold fuel is not completely burned and ends up going past the rings. The early Verados suffered from this issue in almost every incidence I have heard about a new or hotter thermostat cured the problem.

The majority of the time when I see this its because the rings aren’t seated all the way allowing blow by. Lots of times its carbon build. But if it’s running cold that is a very good possibility that that’s what it is. I would check it and make sure it’s running the proper temp first and then do a leak down on it and possibly decarbonize it if necessary.

Yes, “making oil” is the term that is widely used but as everyone knows, they do not actually create oil.
I would check the thermostat first, like others have said. That is likely the culprit.