Kicker making oil

[B.I.]

My mariner 9.9 was choking a little during the last fishing trip of last season. It had made a ton of oil in the crankcase, filled up with gas not water. I flushed it out over the winter, it started right up and ran like a champ the last three trolling trips. I checked it tonight and its making oil again. Any thoughts on what is causing this?

[Music Man]

gas on crankcase is usually caused by carburetor float valve sticking open. Fuel leaks through the carb. into cylinders an then into crankcase. This a common problem with small engines with gas tank higher than engine. Cure by putting inline valve in fuel line before carb. and turn off after each use.

[.338WM]

gas on crankcase is usually caused by carburetor float valve sticking open. Fuel leaks through the carb. into cylinders an then into crankcase. This a common problem with small engines with gas tank higher than engine. Cure by putting inline valve in fuel line before carb. and turn off after each use.

I agree on the cause and the valve is a good backup/short term cure. However, I recommend getting a carb kit and performing a little maintenance and repair.

[B.I.]

Cool, Thanks. The kicker is fueled by the main tank and its not above the engine so it shouldn't, i don't think, be able to push or suck fuel into the engine when its not running, i think that is what you're saying. although maybe a new carb kit wouldn't be a bad idea. My buddy told me bad piston rings maybe?

[.338WM]

Cool, Thanks. The kicker is fueled by the main tank and its not above the engine so it shouldn't, i don't think, be able to push or suck fuel into the engine when its not running, i think that is what you're saying. although maybe a new carb kit wouldn't be a bad idea. My buddy told me bad piston rings maybe?

Fuel can still be pushed by the needle and seat if they are worn or the float is sunk/stuck when fuel expansion occurs. If the rings were worn so bad as to allow the fuel to pass them the engine would not run as it will suffer inadequate compression.

Installing a shut off valve as suggested would be a good test to eliminate such a cause and is a good thing to have inplace regardless.

[Music Man]

If the rings were worn so bad as to allow the fuel to pass them the engine would not run as it will suffer inadequate compression.

Not so. Rings are not 360*. The split ends will let any liquid past each ring. This is more pronounced in vertical engines but will occur in horizintal if there is enough fluid in the cylinder.

[rbuck351]

The choking thing says it. It's running rich because the needle and seat isn't sealing like it should and you are pushing partly burned gas past the rings. If it's filling up while not running then there is a gravity/siphon problem along with the leaky needle and seat. It does need the carb cleaned and check to see if there is any bits of stuff in the seat causing it not to seal. Probably a good idea to just put a kit in it and make sure there is no dirt in the carb.

[.338WM]

Not so. Rings are not 360*. The split ends will let any liquid past each ring. This is more pronounced in vertical engines but will occur in horizintal if there is enough fluid in the cylinder.

If piston rings are so worn as to allow raw fuel into the crankcase, increasing the oil/fuel level of the crankcase while running, IT WILL NOT RUN for the reasons I stated. At a state of rest, piston ring wear is insignificant and fuel can easily makes it's way past the rings.

Often times after an engine has been severly flooded, a engine in excellent condition will not start due to lack of compression caused by washdown of the cylinder walls ( the gas removes the film of oil coating the cylinder walls), compression can fall up to 50% or more. When this happens the spark plugs need to be removed and oil introduced into the cylinders restore compression and engine to restart.

3 Days Ago
B.I.

Kicker making oil
My mariner 9.9 was choking a little during the last fishing trip of last season. It had made a ton of oil in the crankcase, filled up with gas not water. I flushed it out over the winter, it started right up and ran like a champ the last three trolling trips. I checked it tonight and its making oil again. Any thoughts on what is causing this?


Clearly the engine is running fine, therefore, the crankcase contamination is occuring at rest. It may exhibit some symptoms during starting and then clear due to a rich cylinder( may be not noticable since it is under choke anyhow) until the excess fuel is burned.

[B.I.]

Thanks guys. I like what you are saying .338 and hope its not rings. I have a carb kit on the way and will clean her up. where is best to put the shut off valve, outside the cowling right?

[.338WM]

Thanks guys. I like what you are saying .338 and hope its not rings. I have a carb kit on the way and will clean her up. where is best to put the shut off valve, outside the cowling right?

Best location would be low in the supply line nearest to the "T" in as possible. One very good reason for that is if at some point the fuel line to the kicker ever decays to the point it cracks, it can allow air into the fuel system as the main runs and cause a starvation issue with the main, conversly it can exhibit a leak and that is BAD.